The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => A7 & A10 Engine => Topic started by: Greybeard on 27.10. 2017 11:20
-
I've obtained permission from Barry Huron from Ontario to copy and post his comment on Facebook. He says he has more to say about this in Real Classic magazine, October 2017.
Barry was answering a chap who was trying to find a cheaper way to get a roller conversion than SRM.
...modern oil is far better than the old stuff and tolerances for bearings has not changed since the beginning of the industrial revolution. the plain bearing is much stronger and more durable than a roller and is universally used in all engines. the fly in the ointment is the sludge trap in the crankshaft-it is always the left big end that siezes due to it filling up if there is any oil in the tank. i have an A65 engine that ran just fine with .009" clearance and .035" end play so it is clearly a good design. the idea that a modification of dubious durability worth as much as the whole bike is more a matter of marketing hype than engineering excellence. clean out the sludge trap and add a filter and it is a bulletproof design. spending money on a modification will only win you garage races and ultimately devalue a bike in the eyes of the rivit counters that have the money to buy it at your estate sale.
-
Interesting point of view.
I went SRM conversion back in 1984. Got fed up with end float and poor quality pattern bushes. Replaced the combined needle roller/ball thrust bearing in 2009 after many many miles. So for me the durability is proven and not dubious. Would not want to go back to a bush.
First photo is one of the horrors which persuaded me to convert.
On the other hand see second photo the defence of the Vandervell bush from BSA back in 1964. Unfortuately Vandervell dont make them anymore.
So it is all a matter of personal choice.
-
A similar argument often rages among unit Triumph enthusiasts, until someone always points out that Ted Simon (he of "Jupiter's Travels") rode around the World on a bush motor, and with no problems.
How much bigger test can there be?
-
I've done 2 engines with the SRM conversion and 1 without. In hind sight I think I wasted my money on the conversions.
Firstly I'm in So Cal U.S. so obviously the freight charges add a lot to the total cost, and secondly I had one of the SRM bearings fail, I found little shiny flecks in the oil and after removing the timing cover, discovered the small ball bearings were breaking up after 13,000 miles. I sent the bearing back to SRM, as I thought it might be of interest to them and within a month I got a new one in the post...no note. I had already purchased a new bearing from a supplier in Canada, so now I have a spare.
My local bearing supplier told me that a 1% failure rate in bearings is quite common, so I suppose I was just unlucky...didn't play the lottery that week.
-
Back in the 50s and 60s, bikers used thick coffee and washing up liquid for oil, never changed it only topped it up, and never fitted fancy modern filters - just made do with the tea strainer to filter out the chunks of metal. Nowadays, we use engineered oil and change it in half the recommended time or less. Some of us have magnetic sump plugs and are meticulous at cleaning everything. Do we really need to change the original bikes. I'm not fitting a filter, just changing the oil more often - and no conversions!!
Rant over - with the winter lay-up coming, do I leave the old oil in the bike and change it when the rabbits start breeding, do I change it now and leave the new oil in the bike, or do I drain the whole lot off and leave it empty? *dunno2* :-\
-
Many A65s had disastrous problems shortly after new purchase. Sloppy factory build may have contributed to that.
The Devimead/SRM end feed conversion had a market because of all those disgraceful A65 breakdowns. The similar conversions for A10s and unit Triumph 500s were tacked on to the range and people bought and keep
on buying them.
-
There is simply no comparison - the SRM conversion is far, far superior to the original bush. If you ride an A10 or A7 in a low level of tune and are not prone to thrashing it, then fine, the bush will usually suffice. Once BSA uprated the power though on the late A10s and the later unit twins, the bush was at the absolute limit of acceptability. BSA had loads of warranty claims, and many unimpressed customers. The bush can't cope with high revs & power.
My A10 is tuned up, and has been thrashed continuously for the past 34 years. The bush lasted two years, but the SRM conversion has managed 32 years so far - with one replacement a few years back as I'd stripped it anyway.
My bike does a lot of miles, cruises at 80mph on faster roads, and gets revved high through the gears all the time. No bush could cope with what I've put my engine through. You might consider me a philistine for treating my BSA like this, but it's built to take it. If you only potter round on yours (and there's nothing wrong with that) then don't waste your money on an SRM conversion. If you want a bullet proof engine like mine, get the SRM conversion, and nitride your crank at the same time.
-
Point taken t20racerman - can't argue with that!
-
Back in the 50s and 60s, bikers used thick coffee and washing up liquid for oil, never changed it only topped it up, and never fitted fancy modern filters - just made do with the tea strainer to filter out the chunks of metal. Nowadays, we use engineered oil and change it in half the recommended time or less. Some of us have magnetic sump plugs and are meticulous at cleaning everything. Do we really need to change the original bikes. I'm not fitting a filter, just changing the oil more often - and no conversions!!
Rant over - with the winter lay-up coming, do I leave the old oil in the bike and change it when the rabbits start breeding, do I change it now and leave the new oil in the bike, or do I drain the whole lot off and leave it empty? *dunno2* :-\
Used oil has some acidic qualities, I believe this is a byproduct combustion.
I dont think a three or four month lay-up would make any difference, but I would change it out than store it. Its one less thing to do when you bring it back out.
Lee
-
I'm with t20. My A10 Cafe gets flogged (raced for 9 years) and no problems with the conversion. My A7 plunger is on it's third bush and needs replacing now.
Cheers
-
The big advantage I can see from a distance is the fact the bearing can be changed by anyone.
I can get my own bushes close by setting up in the mill, but I don't own a Sunnen hone much less the mandrels needed to do the job correctly.
I think if I was to ever do another A10 motor, I may do this conversion and think deeply about converting the rest of the bushings over to bearings.
Dont get me wrong, there is nothing at all wrong with bushings. Its just that if your not set up with the right tooling it gets pricey quickly and you have to rely on other peoples time line.
Lee
-
To a large extent, the problem wit the bush is way way way over rated.
back when we were young and used the bikes as daily transport we were always looking for reasons not to pull down the engines and accepted that they missed a bit , dropped some oil, blew a bit of smoke, vibrated and did not throw the front wheel skyward the instant you looked at the twist grip.
Now days when they get used once every forest fortnight we are desperate to find reasons , any reason to tear the engine apart.
Now my first BSa was a horrid mix of long & short stroke parts, over carbed & filled with pistons that made a church steeple look flat.
I thrashed that bike without mercy for 3 years till eventually it locked a rod , chewed out the barrel spigot then proceeded to rip the barrels off the flange.
Now there is no such thing as an engine that can not be made to work better by spending a lot of money on it, the question is , do you need to spend the money & will it be good value.
While there were quite a few warranty claims attributed to the plain bush on A 65's. remember that engine is putting out near double what a std A 10 puts out and is a high reving over square engine and not a A7.10 that developes peak power way before an A 65 gets onto its cam.
-
The big advantage I can see from a distance is the fact the bearing can be changed by anyone.
Lee
The fact that you could do your own bearing and could be changed by anyone with basic tools is a BIG advantage. The pain of having to strip down and then find an engineering company to hone and prat about with a plain bush..
What about cost???... How much does it cost to get a bearing conversion done? What is the difference in price Plain vs Bearing?
-
My Star Twin has now clocked up 40 years of use and abuse and absolute thrashing on its plain bearing. Failures of plain bearings are not a design fault. So much is down to the bush and how it is fitted. My wife's A10 has had even more years of thrashing (she's not a delicate flower when it come to the throttle hand) and has never had a problem with the timing side bush.
A lot of this discussion is down to personal experience or belief. It does worry me slightly that new BSA owners feel they must go for the SRM conversion before anything else. It's a lot of money for something that they most likely don't need.
If you are going to hammer an A10, I would look to the ageing con rods as the most likely components to fail.
-
My Star Twin has now clocked up 40 years of use and abuse and absolute thrashing on its plain bearing. Failures of plain bearings are not a design fault. So much is down to the bush and how it is fitted. My wife's A10 has had even more years of thrashing (she's not a delicate flower when it come to the throttle hand) and has never had a problem with the timing side bush.
A lot of this discussion is down to personal experience or belief. It does worry me slightly that new BSA owners feel they must go for the SRM conversion before anything else. It's a lot of money for something that they most likely don't need.
If you are going to hammer an A10, I would look to the ageing con rods as the most likely components to fail.
I do not intend hammering my A7 . I just want it right and reliable (as can be!) . I will use it , not mollycoddle it , defo not thrash it. I may stick to a plain bush then......BUT..it is getting the RIGHT part (C&D Autos?) AND having someone who KNOWS how to machine it correctly .That is my concern.
-
The original bushes work fine but a few years ago there were a lot of two piece bushes about with poor fixings between the inner and outer. This allowed the inner to turn and close off the oil ways. I always fit solid bushes then blue and hand scrape them into line. Not the recommended way but has proved reliable on all the families a10s (some of which get a right hammering by the young-uns.
-
I always fit solid bushes then blue and hand scrape them into line.
I had to learn how to do that when I fitted a new crankshaft to my Austin Seven. The big ends were white metalled and had to be hand scraped to fit the journals. I hadn't realised one could do that with the BSA shaft bushes.
-
I agree with gpo746, both my A10s cover barely 2000 miles a year, so the bushing is probably adequate, especially as I change the oil, which is still relatively cheap, approx every 500 miles. But if you intend to use your A10 as a daily rider, covering many thousands per year or racing then perhaps the conversion is for you, unless you have a bearing failure as I did.
-
My Star Twin has now clocked up 40 years of use and abuse and absolute thrashing on its plain bearing. Failures of plain bearings are not a design fault. So much is down to the bush and how it is fitted. My wife's A10 has had even more years of thrashing (she's not a delicate flower when it come to the throttle hand) and has never had a problem with the timing side bush.
A lot of this discussion is down to personal experience or belief. It does worry me slightly that new BSA owners feel they must go for the SRM conversion before anything else. It's a lot of money for something that they most likely don't need.
If you are going to hammer an A10, I would look to the ageing con rods as the most likely components to fail.
Yes a sore point there.
More than 1 person I know was ardent that their bike would grenade without an SRM conversion but were more than happy to put the old rods back in without as much as a simple dye pen test for cracking.
-
Horses for Courses,,,,,,,, But overall I agree with T20Racer,
Biggest REAL issue in my experience with many rebuilds of British engines, (Not many on A10s admittedly) is that the process of "Blueprinting" is the most important, followed by sensible time change parts replacements with basis of metallurgy and physics.
Blueprinting is the process of checking every surface and dimension and optimizing it to the best possible specs. Not easy, but in my experience (And I am certified in Aerospace inspection and repair (FAA-A&P as well as multiple ratings in NDT-Non Destructive testing) is that many of these old bikes were built to rather loose and sloppy tolerances. For their day they were pretty good and overall I think 1950s BSA stuff was some of the best on the market. But lets be honest. Every manufacturer builds things to a cost, not an engineering/machining ideal. Secondly after 70 some years, dimensions change, especially aluminum castings. In the BSA engines I have checked I have found significant dimensional changes that I am certain did not leave the factory with. But I have also found some really sloppy work as well that was "Good enough to go out the door" and many that WERE NOT good enough to be installed on a bike.
**Norton was probably the worst offender in that dept, and knowingly shipped junk that had to rectified at the dealer level, But all Brit manufacturers were guilty at times of this.
Something that Edward Turner begrudgingly acknowledged after returning from a trip to Japan.
But I wholehearted agree on aged rods and other bits. I bring it up often but in Stan Shentons book "Triumph Speed tuning", Triumphs engineers stated that the service life for a Triumph connecting rod was ONE,, thats 1,.... 500 mile race. Its simply physics that a alloy rod has a limited service life, Math is Brutal!
As to the specifics of a bush vs bearing, I have come to a middle of the road approach. I agree that a low stressed engine will run fine on a bushing if tolerances are kept in line. I also talked to a lot of racers who spent decades thrashing these old engines on their insights. I believe that the bearing conversion done properly is a sound modification.
Triumph ran the early 500 unit twins on bush but they were not without failures (same with the gooseneck frames prior to 67). As the 500 unit gained power it was necessary to upgrade all aspects of the engine.
(Gearbox too) So the castings were improved as well as the bearing change.
***CORRECTION: Ted Simons Triumph he rode around the world on was NOT a bushing model,, It was either a 72 or 73 Model which had many improvements over the early engines. So lets dispel that myth please ***
So, comparisons to cars always come up, and I have built a number of car engines and raced a few. But there is a BIG BIG difference and it comes down to design. The more cylinders you have the smoother the power pulses, which is why for example Jaguar ran a V12, A twin cylinder vertical twin without counterbalancers is a nasty enterprise, which is why Ducati and others ran a 270 deg crank. (Smooths out that nasty vibration) Only Matchless/AJS really got the design right and then failed in execution with their center main bearing. (Sloppy manuf tolerances). This is why the modern Norton 952-961 engine has a center main bearing as that crankshaft whip is extreme. I have the documentation on stress analysis equipment to prove this.
If you guys were to actually see how much these engines flex, whip and bend internally at speed you would never leave the driveway or garage. Some feel that the vertical twin engines of BSA-Norton-Triumph are purposefully weak and flexible by design and some argue that by reinforcing them you invite breakage. If there is any truth to that then you by extension have to acknowledge that parts that flex can only do so for so long and how much. (IE: Time change)
But a bushing in a main bearing application CAN last a very long time in a 4-6-8-10-12 cyl configuration if properly supported. Most of the small block chevy V8s I build are a high nickel cast iron block with 4 bolt main caps and substantial meat. They get line bored and I use seasoned blocks. They dont move or flex.
These old vertical twins dont have any of these benefits and the amount of flywheel flex and whip is extreme. But dynamic balancing is critical. Not the old static balance (Which is better than nothing) but true dynamic balancing is something I wont cut corners on. I have found piston and pin weight discrepancies of several grams out of the box, rods mismatched,Cranks with different strokes between cyls, and then there is rocking couple.
So a BSA A7-A10 puttering around under 4000rpm and intermittent usage will be fine on a bushing, but beyond that they need all the help they can get.
-
***CORRECTION: Ted Simons Triumph he rode around the world on was NOT a bushing model,, It was either a 72 or 73 Model which had many improvements over the early engines. So lets dispel that myth please ***
Turns out you are spot on, and it was a late police model with those nice big mains fitted.
Another old myth busted... *conf*
-
Ted Simon was a guest many years ago at the Oregon vintage MC club annual banquet, seemed like a nice guy.
He gave a short talk and presentation. I did not go that year but I heard it was good evening.
I rather like the later model Unit 500 Triumphs, I would NOT want to travel the US interstate system for any length of time on one, but back roads they are a hoot. Torquey and just a lot of fun. One of my long languishing projects is a Rickman Montessa missing a motor. I have a very nice 1972 Triumph Daytona motor for it and one of these days will see the road again as a enduro. (I have a clear title and registration for the Rickman) I wanted to run a BSA B50 motor in that chassis and BRG along the lines of a Jeff Smith bike but sadly the BSA engine is too tall for that frame. The T100R is a tight squeeze but manageable.
To cut up the Rickman frame is unconscionable so Triumph it is.
-
That's where you and Odgie differ...
-
A similar argument often rages among unit Triumph enthusiasts, until someone always points out that Ted Simon (he of "Jupiter's Travels") rode around the World on a bush motor, and with no problems.
How much bigger test can there be?
I thought he had a lot of problems. Not sure how many were with the bottom end though.
-
Lads,
I have attached an article of 20 years ago. Found it recently.
On topic up to a point. It restored my faith in the basic design of the Timing side bush.
Col
-
So now you have to come up with the follow up story... :!
-
Lads,
I have attached an article of 20 years ago. Found it recently.
On topic up to a point. It restored my faith in the basic design of the Timing side bush.
Col
couldn't agree more!
thanks for sharing article.
-
Lads,
I have attached an article of 20 years ago. Found it recently.
On topic up to a point. It restored my faith in the basic design of the Timing side bush.
Col
couldn't agree more!
thanks for sharing article.
I could only find this; there are a couple of pics if you scroll down, and it seems to be talking more of '85 than '86 I think.
http://zhumoristenouveau.eklablog.com/a-versailles-louis-xiv-recoit-le-paris-dakar-85-a117369820
-
Looks good in the husky frame, you could do a double take and almost think it belonged there! done up with its black paint job.
cheers ;)
http://www.parisdakar.it/category/piloti/#/?playlistId=0&videoId=0
more pics
-
sorry a bit off topic *conf*
-
Hi Dutch, Harvey,
I did also wonder whether Mr Eicher competed in the 1986 Paris-Dakar.
Clearly the article was written just as the 1986 Rally was commencing.
I have been unable to find any reference to whether he competed in 1986, and suspect he didn't.
It appears from the article that he was planning to do so right up to the start of the 1986 event.
So I have just emailed him to ask. His website is at http://www.eicher-classic.ch/.
Awaiting his reply and will advise.
Colin
-
many years ago back in the late 60's there was a firm that did a pure needle roller conversion that had a thrust washer made from phosphor bronze fitted to the timing side and all the bronze bushes were replaced by needle roller bearings, this was before devimead did it, i still have this engine in my loft, it was highly tuned with a polydine cam, 9:1 pistons, gardener carb and many other mods and it went like the clappers, no low down power and a very rough tick over, but it is still on that original needle roller timing side bearing, one major problem with fitting needle rollers to the idler shaft was oil getting in to the dynamo as there was no seal, nowdays you can get those bearings with a seal built in so that would cure the problem. building another engine on simalar lines but with a 357 cam instaed of the polydine as that would be dificult to ride in modern traffic.
-
many years ago back in the late 60's there was a firm that did a pure needle roller conversion that had a thrust washer made from phosphor bronze fitted to the timing side and all the bronze bushes were replaced by needle roller bearings, this was before devimead did it, i still have this engine in my loft
They last forever if you keep em in your loft! *smile*
-
did a lot of miles on it, as it was my only set of wheels at the time so it went every where including a trip to the italian lakes 2 up , proved very reliable although a bit intractable at slow speeds , i think the filtrate 20/50 plus oil helped a lot. pity it is no longer available, then i changed to a castrol strait oil with a graphite aditive and that seemed to work ok, going to rebuild it and put it into a light frame to have a go at hill climbing, seems like a bit of fun that. got a couple of other projects i need to finish first.
-
I hate to stir up trouble again, but I do enjoy it!! *fight*
Recently I was in Bright Victoria, and found this article in a bike magazine at the accommodation I was haunting.
Interesting 1953 test by Enzo Ferrari. As some pointed out, a lot depends on the quality of the plain bearings.
Col
-
B....r, gonna have to get mine put back to bushes and worry about line reaming and end float again. *help*
On a serious note, thanks col, interesting to think there are only plain shells in the van i drive.
*computer* *beer* *bright idea* *beer*
-
Attached January 1964 bulletin from BSA re the Vandervell bearings.
On a personal note my SRM end feed roller conversion has been working with no problems since 1985.
-
G'day Fellas.
Once again I have a foot in both camps. Plain bush in the plunger and bearing in the Cafe. The bush in the plunger has I think lasted 30+ years but was well due for replacement at the recent rebuild. The bearing in the cafe was done in the early 90's for the racer and only replaced after blow ups (barrels parting company from cases) a couple of times. Still delivering full oil pressure to the crank. I'm happy with both.
Cheers
-
Question: Why did the plain bush last so well 60/70 years ago but does not fare well now?
One thing I didn't have a clue about when Bergs built my engine is the line boring, which I presume is how the bush is lined up with the crank???? Sorry if that's rubbish. I think, when RM built my engine originally, he just shoved a new bush in and chucked the rest together (badly). With Bergs and MWAS, the bush was engineered and line bored to the engine, and probably takes account of the amount of damage and wear to the other components. When everything was brand new, this may have been unnecessary. So, maybe the failure rate is down to the fact that bushes are put in without taking into account the tolerance variances of other components due to wear, etc??
I reckon the consensus is not a bad one, heavy, frequent and prolonged use may warrant a conversion. For the rest of us with empty pockets, the bush may have to do.
-
A plain bearing (bush) does not like contaminated oil, so the use of modern oils (without filtration) may well accelerate wear. Also, the original design was, I believe, while metal - which is more tolerant to impurities than the bronze usually fitted today. Type of bronze is important too, but don't ask me - there's a zillion different types - metallurgy is a subject all its own.
-
Question: Why did the plain bush last so well 60/70 years ago but does not fare well now?
heavy, frequent and prolonged use may warrant a conversion. For the rest of us with empty pockets, the bush may have to do.
Think the accent needs to be on the 'heavy' worty. On an initially unknown motor I got 50K miles out of mine before passing it on. At 30K-odd the bush was within the 1.5 thou tolerance and the ends and crank were unworn. A couple of years post-departure she's still running smoothly and well. That's without return line filters or anything except regular oil changes, bog standard 20/50 after cleaning the crank out, and moderate treatment. Which to me was 60-65mph cruising, and not going totally mad with the right wrist very often.
A nicely in-tune engine, upward gear changes when you know you'll be on the cam in the next gear (ie torque not revs) and I reckon these things can last and last as designed.
I don't think there's much point in flogging any of these things to death, because the difference between using full revs or 65-75% - in terms of time taken to get anywhere - isn't very obvious. And the olden day fun of blowing cars into the weeds has long gone - most moderns will see off most old Brit iron, and any 2 wheeler with an engine bigger than a mobile 'phone will too!
-
Cheers Bill/RD. I think that MWAS got a particular type of bush which Bergs rated, but you'd understand that better than me. I had forgotten that I commented earlier in the thread about external oil filters, but that has changed after my experiences. At the end of the day, I don't want bits in the oil being ground into the bush (after seeing the horror of my old one). I'll continue with a mid-detergent mineral to get the debris through the filter, now that I know the sludge trap is clear.
With the regular oil and filter changes, I'm hoping that the motor will have a good life for some time. Bergs said he'd put that motor in his bike, and that's good enough for me.
-
G'day Fellas.
The bush I put in (in the early 80's) lasted quite well considering the flogging it got. The plunger for quite a while was my daily and weekend tourer, had a spell on the race track and was my bush basher. So 40 years since I did it she was making a bit of racket. EIGHT thou up and down in the bush and 5 thou ed float but was still going, mind you I was using 70wt oil to help fill the gaps.
Cheers
-
worty if it starts first kick again the engine is going in mine as mine won't throw over easily with the thick oil i tried it the other day, roll on summer.
-
It does sound sweet. Do I need to remove the PRV again to see if oil is still coming out?
-
worty nooooooo leave the PRV in, i'm going to start calling you Whittling Worty *whistle* your timing side bush is SAE 660 copper lead bronze and other bits nickle silicon maybe, just right for the job. MWAS bought the material to make the bush because they don't make a bush to fit your well ground timing side journal.
-
I believe guzzies get ridiculous mileage from their plain bearing engines.
Do you think the horizontal split cases make a difference?
cheers
-
I believe guzzies get ridiculous mileage from their plain bearing engines.
As do all modern cars / vans / lorries
-
worty nooooooo leave the PRV in, i'm going to start calling you Whittling Worty *whistle* your timing side bush is SAE 660 copper lead bronze and other bits nickle silicon maybe, just right for the job. MWAS bought the material to make the bush because they don't make a bush to fit your well ground timing side journal.
Heh, soz Bergs, just want to do the best for the motor after all the work that's gone into it. How does that bush material compare to the original as a matter of interest?
RD - the Kwaka also has horizontally split cases - is that the 'case' for most moderns?
-
worty the original bushes were steel backed with a pegged bearing material which i believe is not a lot different to yours i think they were made by vandervell maybe white metal on copper like a big end shell. stop worrying it's not got a hard phozzy bronze bush to wear down your already worn journal. go to the pub untill the sun comes out *beer*
-
I have used LG2 for decades
Firstly it is softer than the steel journal and secondly if it gets too hot the lead melts & smears to protect the shaft ( for a while )