The BSA A7-A10 Forum

Technical => A7 & A10 Engine => Topic started by: Steverat on 03.10. 2018 17:31

Title: Piston choice - Hepolite or JP?
Post by: Steverat on 03.10. 2018 17:31
I am in the lucky position of needing to buy a pair of +0.040" A10 pistons, and find the Hepolites offered at less than £100 whereas JP are over £200 (Feked and others). Can you enlighten me as to the difference in value? I always thought Hepolite, as an OE manufacturer, would be more highly valued, obviously not. What is so good about JP? Is there a problem with Hepolite?

Thanks for your views
Steve
Title: Re: Piston choice - Hepolite or JP?
Post by: mugwump on 03.10. 2018 18:02
Hepolite only in name now, unfortunately. They are TAIWANESE made, and come in a deliberately aged looking and authentic packaging. However, they have served me well and I'm assured they are good quality. BUT, the rings supplied with them are crap so if you go with these get some decent rings, which are readily available from somebody like Hastings or Thorntons etc.
I have also had good experience with Gandinis in other bikes.
No idea about JP.
See what others have to say.
Title: Re: Piston choice - Hepolite or JP?
Post by: RDfella on 03.10. 2018 20:20
Original Hepolites were the benchmark for others. Always used them in the engines I rebuilt (incl many marine diesels) in preference to OEM.
When I recently rebuilt my GF I had a set of + .040 Hepolite, but sadly, when boring the cylinders, found the muppet who bored it previously hadn't got the cylinders perpendicular. Had to go to + 060 to clean up, so was obliged to buy fresh pistons. Ony ones I could find were JP. Came in very cheap cartons and the pistons themselves look cheap. They work, but then my GF isn't run in yet. Not overly impressed whith what I saw. I've heard Gandinis, mentioned by mugwump, are good, but never seen them in the flesh. Have Feked still got the original Hepolite + 040 pistons they bought off me when I had to go to 060?
Title: Re: Piston choice - Hepolite or JP?
Post by: Steverat on 03.10. 2018 20:49
I'll ask, thanks
Title: Re: Piston choice - Hepolite or JP?
Post by: berger on 03.10. 2018 21:02
i have not been to the pub, I put those Taiwanese pistons in mine but with Gandini rings and they are doing very well, from the oil ring groove all the way down to the bottom of the skirt it looks like you could use them to saw fire wood compared to the smooth finish of old original pistons , but they are standing up to the abuse I give them *shh* >:D
Title: Re: Piston choice - Hepolite or JP?
Post by: Dipstick on 03.10. 2018 21:07
It was before I discovered this great forum, I bought a set of JP's from a local dealer in Holland. Those were properly packed in a JP carton box so I do not recognise the complaint as mentioned in the previous post of RDfella.   No idea what the quality is....
Anyway, I bought them and have to install the pistons otherwise I am throwing away a lot of money  ;)
Fingers crossed.
Title: Re: Piston choice - Hepolite or JP?
Post by: Steverat on 03.10. 2018 21:13
i have not been to the pub, I put those Taiwanese pistons in mine but with Gandini rings and they are doing very well, from the oil ring groove all the way down to the bottom of the skirt it looks like you could use them to saw fire wood compared to the smooth finish of old original pistons , but they are standing up to the abuse I give them *shh* >:D

berger where did you manage to buy the Gandini rings?
Title: Re: Piston choice - Hepolite or JP?
Post by: ellis on 03.10. 2018 21:21
Andover Norton stock them.

Address: Unit 4 Brunel Gate, Portway West Business Park, Andover SP10 3SL
Phone: 01264 359565


ELLIS
Title: Re: Piston choice - Hepolite or JP?
Post by: berger on 03.10. 2018 22:20
Steverat I seem to think it was burton bike bits and they hadn't got + 40s at the time of asking but within 14 days they got them to me, they are well made and all marked for fitting the correct way, even in a nice box and each in its own packaging with a diagram and instructions-------- also pre gapped
Title: Re: Piston choice - Hepolite or JP?
Post by: groily on 03.10. 2018 22:25
When I needed some for one of my AMCs, the only available option at 8.5:1 was JPs.

I think the critical thing is bore dimensions.  JPs don't come with machining data if I remember right.  If memory serves, about 5 thou skirt clearance was what we went for on 72mm bores. I haven't touched the engine significantly since building it up in early 2013. Doesn't use much oil, is very free revving and goes really well..

If I was faced with using them in the A10 I wouldn't be unhappy. That day cometh, as the +40s in it have done umpteen thousands of miles over 10 years+ and I've already given them one new set of rings.

My latest new ones are GPMs (Gandinis) for a notrun, just a few weeks back. I used them because they're what's available (and what was in there before) but I would have been happy enough to go JP there too if necessary..

Prices for the GPMs  and JPs were comparable at £175+ taxes for the latest ones, and about £160 five years back for the JPs.
Title: Re: Piston choice - Hepolite or JP?
Post by: bl**dydrivers on 04.10. 2018 02:32
I’ve read up so many horror stories with reproduction pistons that I searched for NOS BSA +40 pistons and was lucky to have found them. But will need new piston rings as the NOS ones have some corrosion on them and best to play it safe.
Title: Re: Piston choice - Hepolite or JP?
Post by: John alexandrou on 04.10. 2018 10:31
I bought a set of Hepolite Pistons and rings for my A10 Roadrocket, the rings didn’t bed in properly and forced a second reopening end strip and rebuild, I bought a new set from an Italian manufacturer and the difference was like chalk and cheese, bedded in nicely no smoke etc.,
Title: Re: Piston choice - Hepolite or JP?
Post by: Slymo on 04.10. 2018 13:48
I found the JP Piston I bought for a B44 rather heavy and the rings would simply not bed in. I found on looking at various forum posts that this was a common experience. I ended up with a Hap Jones Piston from the States (although the Piston was made in Japan) which settled in a treat. It may be that there was too much oil around for the JP rings to bed in as I had head gasket issues at the same time but I would suggest that you use the lightest wipe on the bores on assembly.
Title: Re: Piston choice - Hepolite or JP?
Post by: BSA_54A10 on 04.10. 2018 14:09
It was before I discovered this great forum, I bought a set of JP's from a local dealer in Holland. Those were properly packed in a JP carton box so I do not recognise the complaint as mentioned in the previous post of RDfella.   No idea what the quality is....
Anyway, I bought them and have to install the pistons otherwise I am throwing away a lot of money  ;)
Fingers crossed.

If they are the Aussie made JP's you have do not under any circumstance fit them with the original rings.
They will take near 1000 miles of careful running in before they seal.
Toss the rings on evilbay some idiot will buyt them and fit HAstings, Cord or whateveer your favourite ring is .
Title: Re: Piston choice - Hepolite or JP?
Post by: groily on 04.10. 2018 16:11
Yup - the weight of the JPs and the quality (or lack of) of the rings were two worries I had when doing my AMC motor, having heard exactly what's been said here.
In that case, the 8.5:1 JPs at +20 weighed 23 grammes more than the originals at standard bore and 7 point something:1. Not a big difference in that case I didn't think, but not a perfect apples to apples comparison either. How much heavier is a JP for a B44 I wonder, just as matter of interest? Maybe it's a 'singles thing' . . .?

The rings didn't give me any problems either luckily, and 20K kilometres down the road, no reason for concern. To start with, I was definitely very edgy just waiting for trouble to strike. Now, I give it full beans through the gears just so I can hear the sound of a high-revving comparatively shortish-stroke twin with an amplifier for an exhaust.

So dunno - am I just lucky? Or are some versions of JPs better than others? Or does it come down to getting those bores sized spot-on to suit by people used to fitting the things, and just maybe helped by being ultra-careful for the first few hundred km on what was not only a new pistons/rebore/valves/guides/seats/cams/followers job, but also a brand new crank and forged rods  . . . all of which cost a bloody lot of beer vouchers. (There were none left to make the cycle parts half as nice, but that's Ok.)
Title: Re: Piston choice - Hepolite or JP?
Post by: bsa-bill on 04.10. 2018 18:35
Quote
does it come down to getting those bores sized spot-on to suit by people used to fitting the things

yep most good shops given one of the  piston you intend to use should get it right
Title: Re: Piston choice - Hepolite or JP?
Post by: Dipstick on 04.10. 2018 19:13
It was before I discovered this great forum, I bought a set of JP's from a local dealer in Holland. Those were properly packed in a JP carton box so I do not recognise the complaint as mentioned in the previous post of RDfella.   No idea what the quality is....
Anyway, I bought them and have to install the pistons otherwise I am throwing away a lot of money  ;)
Fingers crossed.

If they are the Aussie made JP's you have do not under any circumstance fit them with the original rings.
They will take near 1000 miles of careful running in before they seal.
Toss the rings on evilbay some idiot will buyt them and fit HAstings, Cord or whateveer your favourite ring is .


Yes they're made down under...
Title: Re: Piston choice - Hepolite or JP?
Post by: bsa-bill on 04.10. 2018 19:19
Quote
do not under any circumstance fit them with the original rings.

now your going to tell us there upside down  *smile* (sorry old joke, just had to be said tho)
Title: Re: Piston choice - Hepolite or JP?
Post by: Sluggo on 04.10. 2018 19:40
I have posted frequently on many forums about Hepolites and aftermarket pistons, so dont recall if I recited my screeds here or not in other discussions but Ill try to hit the high points and move on.

Hepolites were a OEM supplier of a cast piston.  Keeping in mind CAST being an operative word.  Generally okay and revered by many, I have used many sets and sold even more.  However I never placed them very highly as some peoples prices may suggest.  (There is some fanboys out there of them)  I still have a few sets in original EARLY packaging so, Surely the early types.  Hepolites over the years had different packaging so you can guess-timate the era of manufacturing by its packing.   The original company was bought up by a US company, they did nothing with it, then broke it into pieces and sold off. There is other vendors now making poor quality parts under that name, I believe under license.   Poor quality is a relative term because I never felt the originals were never more than a cheaply made part, however that low benchmark sunk even lower with the knock offs.

### I grew up building hot rod American V8s...  So a cast piston was a cheap part and not worthy of any self respecting engine builder.  Forged pistons were the minimum benchmark, But economies of scale are much different, And I have had car guys getting into classic British were shocked at some of the prices for pistons. For an approx comparison some years back I ordered a set of Cast Small Block Chevy 350 pistons for a grocery getter.  Less than $100 for 8 pistons, pins and rings.  For a set of much better Hypereutectic Was $160 and premium Forged was $275  FOR a FULL SET of 8!   I had a guy ask about Original Hepolites for a 1961 Triumph Bonnie and he was incensed at the price at the time of $220 for a set of 2.  (He opted for some cycle crafts I had for $90.00)   Now days, some are using all kinds of interesting materials as manufacturing has evolved.  A lot of discussion about Billet, and unthinkable before, but apparently its working out great.  MAP cycle is selling Billets for a range of applications.  Good reports I hear.  ###

Now, when using Hepolites of the original company I have seen a great deal of quality variables.   Pistons are graded and the better ones are matched up, When you turn them over NOS should have small painted dots.. green, red, blue etc.  This means that L-R they are somewhat consistent.  Castings can vary widely so they pair up sets to match.  However its not uncommon to get a set that varies considerably by weight.  Up to several grams.  They can also vary by sizing. CONSIDERABLY between L-R and some Hepo's are absurdly mismatched to proper dimensions.  So, when boring a cyl,, Its mandatory to label them L-R and hand fitted to each bore to correct dimensions as the piston ODs vary with Hepos in most cases.

Verify yourself,  Throw them on a scale and measure with mics & calipers.  Math is Brutal!

With Hepo rings,, again depends upon era manuf,, Some were quite good, (Considering)  However later years not so much.

I have NO experience with JP. However I find the expansion joints on the skirts shocking!  Holy hell that would keep me up at night!   I have seen many decades of mayhem on the Nortons where such joints were a sure fire way to seperate the crown of a piston from the skirts with much damage. Even the later versions with just the holes would break with regularity.  Many pictures online of blown up Nortons with these and the INOA tech digest expressly warns about this.   I have heard of similar on other makes.  Although I have seen a FEW race motors with holes drilled in the thrust face skirts for lightening, But in general a piston is like an egg,, It derives its strength from its integrity of the shell structure so a big slot, seems counterintuitive.    Other than some 2 strokes have never seen that pencil out. (Expansion joints)

Now for 2 decades I was a huge fanboy of CycleCraft pistons.  For a casting, they were excellent quality.  The finish and casting quality was excellent. More importantly I found very consistent piston weights L-R and dimensionally they were so consistent I never found any out of spec.  In some apps.. BSA A65 they were heavier than originals for example.. So rebalancing is important, But I like to balance everything so a minor issue.   However the supplied rings were garbage.. I always used Hepo rings, Hastings or a few others.
I only found one instance of the piston weights being off in 25 years of using them and we caught it early.  I believe that was an anomoly.  I DID find the supplied pins varied but we always weighted them and machined the IDs of the pins to get a consistent weight.  The supplied clips are a spring type and depending on what shows up, I never had a problem but in many cases I used special circlips I ordered for piece of mind.  (There was a raging argument on a NotRun site about bad circlips and grooves)

So, When I was building a LOT of motors (Mostly Triumphs) I would take in 4-6 cyls at a time. (20-40-60-80 in a few cases)  and drop off one set of pistons for each size with my cyl guy.  The consistency of the cycle crafts was so good, I never had an issue with sizing.  If it was for Hepolites??  hell no!!  We carefully controlled each cyl and the pistons to get the holes sized exactly.

I only built a few Motorcycle engines with high end forged pistons, as its a different world than car engines.  The reality is few people actually race or push these vintage bikes hard enough to justify it, so Cast pistons are usually adequate.  However when I hear someone gushing excessively about a Cast Hepolite being the top of the game its amusing.  Its still JUST a casting. And in the world of metallurgy a casting is subpar to other materials.

**One note on sizing.   I still have some old dealer stock with 10 thou increments, but its very hard to find pistons and rings in those ranges.  Back in the day they were supplied in 10 over, 20-30-40-50-60-70 and even 80 over.   I have run Triumph 650s with 80s with no issues and high mileage covered because there was enough meat in the cyl.  However I had a few cyls that were scrap at 60.   Nortons twins the cyls were so irregular you take a serious risk at even 20 over, 40 is exceptional and 60 is a miracle! (Dirt inclusions, dross, casting voids and cracking are the usual rejection issues)
Manufacturers typically only offer ins 20-40-60 these days unless you can find some old dealer stock, then HOPE there is matching rings.   ALSO note over the years, some pistons changed Ring designs,, which is a whole different topic, But the ring grooves HAVE to be checked they are suitable for the rings and vice versa
Check ring groove WIDTH and DEPTH!

I have had conversations with some of the largest US wholesalers and its painful for them to stock pistons for the more common BSA-Norton-Triumph  as to get pistons made now requires huge orders in each size to get them done.  Often these wholesalers will work together.  (MAP-JRC-Walridge-British ONLY-and Healys operation-Coventry Spares).   You guys are not riding enough and ordering enough.  It can take YEARS to sell off enough pistons to justify a re-order.     BSA A10s are considered so obscure very few people will bother to stock parts for them.  BSA A7???  Ha!  Good luck with that!
Title: Re: Piston choice - Hepolite or JP?
Post by: Sluggo on 04.10. 2018 20:43
Just to clarify supply chain mgmt..

The cycle crafts dealer prices were around $45-55 per pair w/ no rings but included pins & clips, Retail varies by seller by typically $80 a pair.  A comparable pair of Hepolites were retail around $160-220  this is for a Triumph 650 twin and a few years ago.  But that should give you an idea.

I know directly the largest wholesaler was having a hard time getting stock from Cycle Craft because CC was doing 10,000+ piece orders for most Asian manufacturers so it was laughable when Bill called to order 100 pairs for each size. (20-40-60) and thats for faster moving stock like Triumph.  Unit  BSA and Norton twins stock moves even slower.  As the largest dealer supplier in the US (Wholesale only) Bill asked me what I though he was moving on Norton twins.  My guess was not even close.   He had sold under 20 pairs of Norton pistons in a year  (You guys arent riding enough)   So, the MINIMUMS for pistons orders keeps going up, and demands down.  Tough market.   As a financial reference,, its poor economy to tie up thousands and thousands of dollars in poor moving stock.  So Dealers would go in on group buys for pistons.

Now, CC seems to have severed production of vintage bikes.  I am seeing products instead branded by EMGO, They look the same.. and assume they are okay.   But here is my advice.  If you guys want to see your beloved Preunit BSAs on the road at all,, You need to stock up on consumables because the supply is fading fast.  I just dont see the incentives to produce such small batches of pistons, valves, rings, and bearings that are proprietary for BSA applications that have no cross over to other makes and models.

My friend Charley who does all my cyl work specializes in 2 strokes and you can often repurpose a cyl or sleeve for obscure applications but not so much on vintage  British 4 strokes.

Heck, at the DGR ride was chatting with a Buell owner and I own some Tube frame and XB Buells and he asked what am I doing for parts,, as some are now already UN-OB-TAIN-IUM  so the writing is on the wall you guys!     

Look at it this way...If you shuffle off this mortal coil before you use the parts, make sure they are labeled and what they go to so your estate or family can sell the bike AND the spares to keep the machine operational, It also adds value.   Otherwise all these bikes will be just like that RUSH song about the Red Barchetta.

-----------------------------------------------------------
Music: Geddy Lee and Alex Lifeson
Lyrics: Neil Peart

My uncle has a country place, that no-one knows about
He says it used to be a farm, before the Motor Law
Sundays I elude the ‘Eyes’, and hop the Turbine Freight
To far outside the Wire, where my white-haired uncle waits

Jump to the ground
As the Turbo slows to cross the borderline
Run like the wind
As excitement shivers up and down my spine
Down in his barn
My uncle preserved for me an old machine –
For fifty-odd years
To keep it as new has been his dearest dream
I strip away the old debris, that hides a shining car
A brilliant red Barchetta, from a better, vanished time
Fire up the willing engine, responding with a roar!
Tires spitting gravel, I commit my weekly crime…

Wind in my hair –
Shifting and drifting –
Mechanical music
Adrenalin surge –

Well-weathered leather
Hot metal and oil
The scented country air
Sunlight on chrome
The blur of the landscape
Every nerve aware
Suddenly ahead of me, across the mountainside
A gleaming alloy air-car shoots towards me, two lanes wide
I spin around with shrieking tires, to run the deadly race
Go screaming through the valley as another joins the chase

Drive like the wind
Straining the limits of machine and man
Laughing out loud
With fear and hope, I’ve got a desperate plan
At the one-lane bridge
I leave the giants stranded
At the riverside
Race back to the farm
To dream with my uncle
At the fireside…
Title: Re: Piston choice - Hepolite or JP?
Post by: RDfella on 04.10. 2018 21:05
Have to disagree with sluggo re Hepolite pistons. Maybe we’re talking different eras, but in the 70’s, 80’s and 90’s when I was building at least one engine (road cars, race cars, boats, m/cycles) a week, I almost always used Hepolite instead of OEM (ie Ford or any other manufacturer). Never had an issue. Yes, cast pistons for 2,500rpm diesels, road cars and cooking motorcycles, but forged for anything that might get a thrashing. In those days Hepolite led the way, not only in piston quality, but alfin cylinders, steel piston inserts and the like.

BTW, does anyone know the preferred balance factor for an A10? I didn’t bother with my recent rebuild as it’s only for road use, but I notice vibration starting around 2,700 (guess, no rev counter) that comes in fairly quickly and maintains the same to max revs (or at least as far as I’m prepared to push a motor with alloy rods). I remember when Chevrolet carried out testing on alloy rods. They only lasted a couple of million cycles – that’s around five hours at 7,000rpm. Aluminium fatigues and work hardens; witness the number of BSA rods that have exited the crankcase (mine, at one time, for example). Would never be my choice for a rod.
Title: Re: Piston choice - Hepolite or JP?
Post by: muskrat on 04.10. 2018 21:15
G'day RD.
62 to 65% is the recommended figure.
I went a bit higher to 72% and it's pretty smooth up top (5-7000) but at 1-2000 she'll walk out the door.
Re alloy rods, I think BSA put a life span on them of 80,000 miles. I never had a rod go when racing the A7SS with 14:1 compression and revving to 7500. Lifted barrels and snapped cranks but never a rod.
Cheers
Title: Re: Piston choice - Hepolite or JP?
Post by: RDfella on 04.10. 2018 21:20
Just to add to my last post, the fact our bikes have become classics should mean parts will be more readily available than they were a few decades ago, not less. As an example, I have a '46 Ferguson the family has had from new. It has the continental motor and when I rebuilt the engine in the early seventies parts were getting really hard to find. It was an old tractor, Ferguson wasn't interested any more, and by the time the eighties came around, nothing was available. When I needed some pistons, there was no chance. Eventually I found a set of four for a 50's Plymouth car that were the same, but 3 1/4" dia instead of 3 3/16". Ideal, as I could bore the liners + 060. Nowadays, forty years later, virtually everything is available. Pistons & liners (three sizes) exhaust manifolds, valves. Everything. Why? Because they are no longer old tractors, but classics that people are doing up, thereby creating a demand. I feel it is the same with our bikes. So much more is now available than was the case twenty or more years ago. Sure, some of the parts may be of questionable quality, but remember that twenty or thirty years ago thare were no parts at all.
Title: Re: Piston choice - Hepolite or JP?
Post by: Steverat on 04.10. 2018 21:25
I have bought the new foreign Hepolite pistons but with NOS genuine British Hepolite rings to fit, all from Burton Bike Bits for £163.13 total.
Thanks for all your help and advice!
Steve
Title: Re: Piston choice - Hepolite or JP?
Post by: Sluggo on 04.10. 2018 21:36
Have to disagree with sluggo re Hepolite pistons. Maybe we’re talking different eras, but in the 70’s, 80’s and 90’s when I was building at least one engine (road cars, race cars, boats, m/cycles) a week, I almost always used Hepolite instead of OEM (ie Ford or any other manufacturer). Never had an issue. Yes, cast pistons for 2,500rpm diesels, road cars and cooking motorcycles, but forged for anything that might get a thrashing. In those days Hepolite led the way, not only in piston quality, but alfin cylinders, steel piston inserts and the like.

BTW, does anyone know the preferred balance factor for an A10? I didn’t bother with my recent rebuild as it’s only for road use, but I notice vibration starting around 2,700 (guess, no rev counter) that comes in fairly quickly and maintains the same to max revs (or at least as far as I’m prepared to push a motor with alloy rods). I remember when Chevrolet carried out testing on alloy rods. They only lasted a couple of million cycles – that’s around five hours at 7,000rpm. Aluminium fatigues and work hardens; witness the number of BSA rods that have exited the crankcase (mine, at one time, for example). Would never be my choice for a rod.

When you were building these motors, what kind of anomalies did you find with piston weights and measurements when using Hepolites??    I have zero experience using them for anything other than Motorcycles so perhaps cars, lorries and locomotives were a different kettle of fish.  But for motorcyle applications I would measure them on a scale and see what the difference was L-R for weights.  I saw many with significant weight differences sometimes up to 2 grams. (often less but still significant)  I surmise that could have a significant impact on vibration wouldnt you agree? 
Usual fix was to take a die grinder and carefully use a carbide or sand paper roll and take some material off the undersides in non critical areas to even them up.
When it came to measuring, It was common to see big deviations from established specs, so back in the days manual specs usually were 3 thou piston to wall,, modern day much looser (4 to 4.5 thou) but when the OD of a piston exceeds those numbers, you will have a problem getting clearance right so either hand fit each piston to each bore, (Hone to spec) or turn down the piston exterior to spec.

As to cast vs forged,, I was illustrating that these are 2 different qualities and specs, However many owners dont know the difference or aware of that.  They go simply for brand name recognition.  However a Cycle craft made in Asia as a cast piston was in my experience vastly better quality at 1/3rd to 1/2 the cost to the OEM Hepolites.  Yet some persisted that the CCs were asian made junk.

I do agree with the alloy rods, valid point.  Stan Shentons Triumph Speed tuning quotes Triumph factory engineers as saying the life of a OEM Alloy rod was one race at race speeds.  However if a plodder and sunday driver,, many can get a lot of life out of a alloy rod with little worry.  If your machine is a significant investment new rods are a sensible expenditure.

BSA Goldstars are a prime example... While many in their heyday ran them competitively with the stock cranks and rods,, these days any sensible Goldie owner will opt for a Pearson Crank assy and Carillo rod, or many are using the ABSAF kit.  The value of a Goldie (And parts) makes anything else foolish economy.
Title: Re: Piston choice - Hepolite or JP?
Post by: Sluggo on 04.10. 2018 21:57
Just to add to my last post, the fact our bikes have become classics should mean parts will be more readily available than they were a few decades ago, not less. As an example, I have a '46 Ferguson the family has had from new. It has the continental motor and when I rebuilt the engine in the early seventies parts were getting really hard to find. It was an old tractor, Ferguson wasn't interested any more, and by the time the eighties came around, nothing was available. When I needed some pistons, there was no chance. Eventually I found a set of four for a 50's Plymouth car that were the same, but 3 1/4" dia instead of 3 3/16". Ideal, as I could bore the liners + 060. Nowadays, forty years later, virtually everything is available. Pistons & liners (three sizes) exhaust manifolds, valves. Everything. Why? Because they are no longer old tractors, but classics that people are doing up, thereby creating a demand. I feel it is the same with our bikes. So much more is now available than was the case twenty or more years ago. Sure, some of the parts may be of questionable quality, but remember that twenty or thirty years ago thare were no parts at all.

Could & should vs reality is 2 different things.  If the demand is there, Sure,, someone will produce a product for it, However it all comes down to economies of scale.   While Vincents are not a common bike and generally considered rare, because they have some passionate owners you can nearly build a new Vincent from parts, albeit at an exorbitant price.   You can build a new 1969 Camaro, or Chevelle as barleycorn makes all new bodies and there is multiple suppliers for every nut bolt & assy, but again,,, at a very dear price.  Same with MG and Triumph sports cars.   The parts supply for POPULAR makes and models of vintage British is generally better than anyone has a right to expect and surprising really.   But thats only on models that have enough demand.   For example Lowbrow customs, one the largest online sellers for vintage bike parts does not stock ANY parts for a Preunit BSA.  They do have limited Unit BSA A65, A little Norton and a LOT for unit Triumphs, but only scattered parts for a Preunit Triumph.  No 441 or C15 single parts.
I know most of the major players,  Mark Appleton of BCS, Mike P at Walridge, Marino & crew at MAP, Bill of JRC, John of Coventry Spares, and only in passing that shifty character at British Only, Bob & his son Mike at Rabers parts mart (Now closed)  and they will all tell you the same thing about supply and demand,

While its amazing we can get ANYTHING at all,, Some may not like hearing it but Preunit BSA twins are not in the same ballpark and the demand is so low, we are fortunate that any one sells parts for them, and I dont see that improving.

If you think that is harsh,,, I have some Matchless bikes.  THOSE get no love at all.  Only true nutters have them and if it were not for the owners club and spares scheme, they would be totally extinct by now.  I have some friends who restored them and its very hard to even recoup 2/3rds of the expense when you sell one.

If you doubt that,. I have some G3 and G12 parts I would like to sell you.
Title: Re: Piston choice - Hepolite or JP?
Post by: trevinoz on 04.10. 2018 22:23
Standard balance factor is 54%. 65% for racing.
Title: Re: Piston choice - Hepolite or JP?
Post by: muskrat on 04.10. 2018 23:20
Yes thanks Trev. Why do I always go to the extreme?
Ah I know. Lots is good, more is better and too much is just enough!
Cheers
Title: Re: Piston choice - Hepolite or JP?
Post by: berger on 05.10. 2018 00:57
I have just weighed 2 genuine STD BSA pistons and 2 +60 possibly made in Taiwan and I have a question I hope could be answered. BSA piston 8to1 comp stamped BSA 67/1443,. 210 point 4gms
also stamped 46/2/69
BSA piston number two BSA 67/1443  then  number 6.7/66
 weighs 212point 8gms
what do the other numbers mean??
other pistons +60thou one is 241gms and other is 239point 9gms , not very interesting but I have no idea what the other numbers mean on the genuine BSA ones , anyone know?
Title: Re: Piston choice - Hepolite or JP?
Post by: Slymo on 05.10. 2018 01:59
Here in NZ we have always suffered from a scarcity of spares. EBay and t’internet have reduced the problem but what happens when you’re looking for something truly obscure pistonwise is you go to Franklin Engineering who for an economically viable (for them) price will make them for you bespoke from appropriate blanks. Alternatively you can find something that will match. I have a mate who runs a Hyundai diesel piston in his 30’s Panther 100 with unqualified success.
Title: Re: Piston choice - Hepolite or JP?
Post by: Peter in Aus on 05.10. 2018 04:40
I fitted JP pistons and rings to my A10 and have had no trouble
Title: Re: Piston choice - Hepolite or JP?
Post by: cyclobutch on 05.10. 2018 08:38
Mmmmmmmmmmm - Rush. A favourite back in the day.
Title: Re: Piston choice - Hepolite or JP?
Post by: BSA_54A10 on 05.10. 2018 08:50
FWIW JP are by and large a bespoke piston maker.
Any size min batch size is 5.
In order to keep stock of blanks low the gudgeon bosses are larger than sd pistons so they can shift the position of the pin a bit.
We have been supplied 2 of the same pistons made from different blanks so you must specify if you want a matched pair.
The landlord just bought the last 550 cc sloper piston for $ 275.
The down side is he buys his rings from a local ring maker who used to supply the auto industry so generally they are too hard for motorcycles with C I bores.
Fine if you have fitted a steel sleeve. Thus we toss his rings on ebay & buy new ones.
I get mine from Total Seal as I can order them by diameter width & radial depth.
Ask them for A 7 ones & they will have no idea what you are talking about.

John Healy mentioned some time ago the minimum order for pistons out of the Tiawanese factory where all of the aftermarket pistons are made is 2000 pairs and he sells less than 100 pair of BSA pistons a year.
To make the production price economic they need to be ordered in 10,000 pairs which is about 20 years supply world wide.
At $ 100 pair you are looking at 20 different size pistons for A's x $ 100 X 10,000 = $ 20,000,000
Even with the current low inflation you are making a loss on every pair you sell after 5 years compared to what you would have made on a term deposit or government bonds.
So it is uneconomic to get pistons made for stock.
I do a lot of riding but in the past 25 years have only put 84,000 miles on the M20;  45,000 miles on the B40's and about 15,000 on the A65.
In the 25 years I have bought 2 Std NOS Army pistons for the M20 & one piston each for the B40's from George Heggie when he was in Narwee & a set of +40's for the A65 in 1986
To put that into perspective, George traded out of Greenacre for 7 years & has been dead for around 15 years.
Now when I was in my youth and the A 10 was the only transport I bought a set of pistons every couple of years, usually from Joe ( Allparts ) or Doc Kelly ( Doc's Speed Shop ) and both of them have been dead for a decade or more.
There are over 2000 different BSA pistons which unless some one knows a very benevolent millionaire with a bent towards supplying pistons for obsolete motorcycles we are left with paying $ 200 - $ 400 a pair for bespoke pistons, it is just a matter of economies.
OTOH if every one on this list wants to toss in $ 15,000 ( AUS ) we could get a run of each size pre unit A series pistons, any one got space in their backyard for a container ?
Title: Re: Piston choice - Hepolite or JP?
Post by: RDfella on 05.10. 2018 13:34
Berger - your piston weights show each pair are pretty well matched - but that the 'other' pair are significantly heavier than the BSA ones. That is of concern, because whilst the difference betwee two of each pair is negligible, the extra weight of the 'others' at almost 60 grams (2 ounces) could have a slight effect on vibration by altering the balance factor.
Title: Re: Piston choice - Hepolite or JP?
Post by: RDfella on 05.10. 2018 13:41
Some very interesting comments turning up.

Agree with Slymo – my 800cc vee twin has modified Fiat 131 pistons. And sand casting a piston should actually be within the scope of a competent DIYer. The pattern required would be fairly easy to make. I recall one sprint bike that was the first locally to achieve 100mph – using a piston made on a TREADLE lathe.

Trev and Musk – I’d expect maybe a 2% difference, but 54 / 65 sounds a lot. If that’s to get smoothness around 5k it must be rough as hell low down. B31’s are 58% and pretty good at that.

BSA-54 –  2,000 different BSA pistons sounds a lot. Even if it’s true, our requirements are far less. As Slymo suggests, the more unusual models cannot realistically be catered for and owners will have to make do. For the rest, I’d guess about 30 models would cover most BSA classics that are actually ridden. Three sizes would be adequate – 030, 040 and 060 – which makes around a hundred. Add in a few models with alternative compression ratios, and we’re still under 200 types of piston. Now we’re not talking pressure die-casting here (something I’m well acquainted with) so I’m surprised someone hasn’t set up to sand cast small batches of, say, 50 of each of the most popular ones. Less popular ones could be cast to order, with machining carried out on an as required basis as orders are received.
Other manufacturers (eg Triumph, Velocette, Norton) made fewer bikes and models than BSA. and many of those would fall into the ‘unusual’ bracket nowadays, so to cover the spectrum of commoner British motorcycles would not be beyond economic feasibility.  Or is that what BSA-54 is telling us JP do?

Sluggo – couple of answers to your queries ..
I agree, different engines need different approaches. I always checked sizes (always found within .0005) and bored / honed to fit. Weights I didn’t bother about unless a race or fast road engine. Quality pistons from the same box are very close. You don’t get paid for doing unnecessary work. A piston from an average diesel engine will weigh around five pounds and the conrod not much less, so a gram here or there is of no consequence. Add to that the need on some to machine the piston crown to get correct bump clearance, and we’re talking ounces, not grams. If a lot of crown machining was required (sometimes including deepening valve pockets) then I would weigh. Only time I would weigh a piston for a single cylinder (motorcycle) is if I was making a change – eg to a high comp piston, which would be heavier and depending on the difference I would want to check the balance factor.
Parallel twin engines were rare in my workshop, but agree that with their susceptibility to vibrate they might benefit from matching. However, if the pistons are of good quality there’s unlikely to be variations sufficient to affect a road bike. I’d be more concerned about the total weight and its effect on balance factor, as vibration is more likely from the latter than the former. If in doubt, the only way is to set the crank up on parallels and check. If going that far, and unless there is a known good balance factor for the engine / frame assembly, I usually modify the flywheel so balance can be altered without dismantling the engine again. Especially useful on newly-designed engines or when a frame has a different engine (eg Triton) when the balance factor can only be a guess.
My present nightmare is a Weslake engine in a sprint bike. By rebalancing I can reduce vibration to almost acceptable levels at low revs, only to be riding a jackhammer at 5,000. Or vice-versa. One of these days it’s going to fall to bits on the start line so I’m currently modifying the frame in an attempt to change frequencies.
Never known a Gold Star rod to fail (not to say some didn’t). The bikes I raced did hundreds of hours on methanol at 13:1, but then I always kept under 6,000 rpm. Best way to ensure rod reliability is not to ding it and cause a stress-raiser. I always protect rods right up to cylinder going on.
Just have no confidence in alloy rods. Never had, but then again if you saw the rough, spindly rods in Jaguar XK and early Aston engines, you’d wonder how they stayed inside either. Usually. I did see one Jag rod outside, but it was being raced at the tim
Title: Re: Piston choice - Hepolite or JP?
Post by: berger on 05.10. 2018 16:02
RD fella if I use the heavy pistons in an engine I am getting round to building one day *work* *whistle* I am having it all sent away to be balanced, I am dying to know what the other numbers stamped on the beezer pistons means *conf2*
Title: Re: Piston choice - Hepolite or JP?
Post by: Slymo on 05.10. 2018 20:50
The happy and sad thing is that as these machines get older and rarer they will become more valuable. There is for instance little problem in buying Brough or Vincent parts but you do need a capacious wallet. A friend with a twenties Norton 18 flat tank has just bought a speedo drive made I believe in the Czech Republic. Very pricey but not a problem when you consider the value of the machine.
Title: Re: Piston choice - Hepolite or JP?
Post by: Kickaha on 05.10. 2018 21:11
FWIW JP are by and large a bespoke piston maker.
Any size min batch size is 5.

We can (or used to be able to) order batches of 4 forged pistons for around $1200-1400 NZD from the likes of Ross or JE,  you could get two in standard bore and the other two in the next oversize
Title: Re: Piston choice - Hepolite or JP?
Post by: Sluggo on 05.10. 2018 21:53
I think i sidetracked this guys thread more than enough. As is typical on many forums, what WAS a simple question spun off into tangents (Im told im really bad about that). 

So, yes,, 2 grams between a pair is significant in my opinion, But I had been thinking for some time of starting a tech thread on blueprinting, balancing and engine design, some which would use some Non BSA examples but all relative and illustrative....

I am certainly not the worlds leading authority on anything, But I DO have a lot of experience in a range of fields and importantly,, I try and find the smartest people out there who are experts, And harvest as much info as I can.   So, I will ask admin If I can start a sticky and add to it, with pictures, graphs and data as well as cover a lot of this material.  I have been looking for a place to park my data from Sir Eddy as well on his methods of blueprinting and I took photos of a BSA Unit motor that was grossly out of dimension so a great example.  I had intended to put this up on BritBike, but Morgan kicked me off!  (Morgan, the real story is far less interesting than what you were told)

In addition, I have some great examples to illustrate this stuff with.  I worked aerospace and product development and process engineering with a range of applications, And I OWN Norton America..  What did not go to the UK to Stuart I have here, Including prototypes, test pieces and ALL the company materials including all the engineering, stress analysis and development work.  (Stuart has given me permission to use this material, and We are using it for education and outreach for our museum as this is an Oregon USA story as well).   I also have access to the technicians who did all this work and doing more interviews as well.
So, when it comes to making a vertical twin I have a lot of resources on hand.

Dont hold your breath for anything overnight,, I move slow, But Ill ask admin to help set something up.
In the interim tell Morgan what he is missing!
Title: Re: Piston choice - Hepolite or JP?
Post by: KiwiGF on 05.10. 2018 22:45
Another shameless plug of my post on balancing, in relation to this thread on Pistons it has some info on piston weights, it can be seen the weight of gudgeon pins is also important. JP Pistons were not unduly heavy as some think.

I’ve read over size Pistons can be relatively heavy as the makers just make (cast?)  one size then machine the OD down for each oversize  *dunno*

I fitted std size JP flat tops with the rings supplied over 5 years and 8000 miles ago with no problems.

https://www.a7a10.net/forum/index.php?topic=6086.msg41598#msg41598
Title: Re: Piston choice - Hepolite or JP?
Post by: BSA_54A10 on 06.10. 2018 10:36
FWIW BSA used one blank for 2 or 3 different oversizes.
And yes there are 2000 different piston sizes.
BSA made a lot of different engines from the winged wheel to the 550cc model H single.

As for machining them to order, way way too expensive as the set up takes a long time even with dedicated machines
Usually the pin is milled flat both inside & out then bored & ground to spec with a final hone.
The piston is then mounted by the pin holes on a mandrel so that it is concentric to the rod.
The piston is then turned to size then ground oval ( where required ) then the ring groves cut.

Lots & lots of set up time & checking time.

Gravity sand casting pistons is not easy to control the filling of thin walls and get a reasonable grain size.
Let alone things like hydrogen adsorbtion which will cause the piston to grow as it gets hot.
Title: Re: Piston choice - Hepolite or JP?
Post by: Slymo on 06.10. 2018 12:47
Burt Monroe cast his own I believe. There is Roger Donaldson documentary  footage of him using a bunsen lamp to melt the alloy and heat the mold. 
Title: Re: Piston choice - Hepolite or JP?
Post by: bikerboy on 07.10. 2018 15:45
If you have not bought any yet I went to TMS in Nottingham for my pistons and I cant remember the make but they were not heppolite.

I have to say they are absolutely excellent 10000 miles later and I have no complaints at all
Title: Re: Piston choice - Hepolite or JP?
Post by: BSA_54A10 on 08.10. 2018 06:36
Burt Monroe cast his own I believe. There is Roger Donaldson documentary  footage of him using a bunsen lamp to melt the alloy and heat the mold.

Ad so did a lot of local racers over here.
We call them Anthony Hordern pistons whose logo was "while I live I grow" and grow the home made pistons do.
Sid reckoned he got 1 good piston out of 5 and remember these are pistons for race engines so running massive clearences.
You can melt aluminium on your stove top, on a lead pot burner, with a kerro blow torch, in an open wood fire.
However if you do not have a reducing flux over the top you will loose a lot of aluminium to dross.
If you do not degass it before pouring then you will get a "special lightweight" piston with up to 5% hydrogen as discreet atoms dissolved into the lattice.
If you are making paper weights or cheap garden furnature then fine ut as soon as the alloy exceeds 200 C these dissolved atoms of Hydrogen start to move through the lattice and they bump into each other to for a Hydrogen molecule ( H2) . However that requires 9 times the space as 2 single Hydrogens and this puts stress on the lattice causing the part to get larger. And by larger it can go tobetter than a 10% increase in size.

So yes Burt cast his own pistons, and if he was lucky probably 1 in 5 cast properly and of those 1 in 5 about the same number would machine cleanly and of those probably 1/2 failed in service.
Back in the day there were a lot of DNF's in every race.
Title: Re: Piston choice - Hepolite or JP?
Post by: Peter in Aus on 08.10. 2018 09:14
I don't think I will bother casting my pistons I will just use JP! ;)
Title: Re: Piston choice - Hepolite or JP?
Post by: Slymo on 08.10. 2018 11:34
There were lots of "Sacrifices to the Gods of Speed" on his shelve that is true. I too would happily use a JP piston again but I will source the rings from somewhere else.
Title: Re: Piston choice - Hepolite or JP?
Post by: coater87 on 08.10. 2018 22:13
 Didnt Wisco make some decent A10 pistons at one time?

 Lee
Title: Re: Piston choice - Hepolite or JP?
Post by: chaterlea25 on 08.10. 2018 22:43
Hi Lee,
Yes,
Cake St Classics had Wiseco make a batch some years ago
They were 9:1 compression
I do not know if they are still available
I have a pair to go into the RGS engine build

John
Title: Re: Piston choice - Hepolite or JP?
Post by: Colsbeeza on 09.10. 2018 02:33
Hi Steve,
I went through the headache of finding rings recently for my Flash. It has new bores at 70.5mm, but were glazed with only 40 miles running due to issues I have detailed elsewhere on the Forum (Smoking), so replaced the rings as a precaution. The pistons were 25yo Hepolites, so presumably English-made.
I purchased a set of Gandini rings locally with the specification on the package blotted out due to the poor condition of the package. The ring measurements did not match the old Hepolite rings.
I finally purchased a set of AE Hepolite rings from SRM, being fairly confident that they know their stuff.
The AE's did match the original spec and also my old rings, although the AE's do have more Back clearance - along the lines that Hastings recommend. I have attached the measurements, which also show clearances both either top/bottom of the ring and back clearance.
If you are matching new rings to existing pistons, the only advice I can give is to make sure the supplier is prepared to take them out of the package and measure both the thickness and depth before parting with your hard-earned. After trying this with Draganfly for two weeks, I gave up.! *problem* They did eventually do so, but by then I had already ordered from SRM. Draganfly's new Gandini ring spec did also match.
After getting the head done up, de-glazed the bores and fitted the new rings, I have re-assembled and run the bike fairly hard but variable for 5 miles - still some smoke and oil on left cylinder. *eek* Given the issues I found with the engine, I was just too smuggly confident to check the breather system and a few other smoke sources. Those little jobs will be next before I do serious miles on it. Geez it ran like stink though.!!
Col
Title: Re: Piston choice - Hepolite or JP?
Post by: Steverat on 10.10. 2018 22:06
Hi Col
Burton Bike Bits very kindly sold me some new Hepolites with some NOS British Hepolite rings. I'll take your point and have a look at he clearances before I bolt everything up.
Thanks
Steve
Title: Re: Piston choice - Hepolite or JP?
Post by: RDfella on 10.10. 2018 22:22
Colsbeeza - am surprised at the variation between rings in your table. The measurement that's most important (assuming there's adequate back clearance) is the fit in the lands. Too much gap, and the lands will fail through hammering. Too little and the gases won't be able to get behind the ring to seal it to the cylinder wall or, worse still, the ring will get nipped in the piston and fail to seal at all. From your list, it seems OE Hepolite is the only correct match.
Title: Re: Piston choice - Hepolite or JP?
Post by: berger on 24.02. 2019 22:33
steve there's this thread to refer to people have mentioned suppliers
Title: Re: Piston choice - Hepolite or JP?
Post by: Rocket Racer on 25.02. 2019 03:32
On a Norton Atlas I used JP's and nothing but problems with several sets, I wouldnt use them again if I was paid to, but know people that both swear by, or at them.  I fall into the latter camp. Seize the day is their motto  *whistle*
Have a set of +80 Gandini's awaiting fitment to my road rocket but the compression ratio is a bit low as for a track motor.
Title: Re: Piston choice - Hepolite or JP?
Post by: ironhead on 25.02. 2019 04:25
As groily mentioned earlier JP's need at least 0.005" skirt clearance. They grow & always have.
Title: Re: Piston choice - Hepolite or JP?
Post by: Scott and Jay on 07.03. 2019 01:50
Hi,
On this topic I like to refer back to my posts on IMD pistons and rings - better, I believe - than either JP or Hepolite (made in UK)..