The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => A7 & A10 Engine => Topic started by: Angus on 06.12. 2012 19:41
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Storing away bits and piece not used in the rebuild and I was wondering should I keep the old pistons.
They appear OK no scoring or obvious damage.
Assuming they are worth keeping, is there any way to tell what they are, compression and + size as I can not see any markings on the crowns and it was over 30 years ago I took them out.
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If they are still in reasonable condition I would keep them. You or someone else might be able to use them oneday.
As for compression, if the tops are concave (dished) then they are about 6.5-1, if the tops are flat with small cut outs for the valves then they are about 7.5-1 and if they have raised bevelled tops with cut aways for valves then they are about 8.5-1. There are of course other variants but they are the basic ones.
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In my opinion, anyone who fits old used pistons into their engine needs their head tested!
Throw them away and save someone from waisting time and energy doing a foolish thing.
They do make fun ash trays though!
Regards,
Julian
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I tend to agree Julian. But, time, cost and location can have a bearing on things. I have two sets, both with under 1000 miles use, waiting for a rainy day. I would never re-use rings.
Cheers
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I'm with Julian, this one, out of an old truck has given sterling service for years!
(http://)
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I tend to agree Julian. But, time, cost and location can have a bearing on things. I have two sets, both with under 1000 miles use, waiting for a rainy day. I would never re-use rings.
Cheers
There are of course exceptions to every rule, ;)
It just makes me cringe though when you see adverts saying "Bike completely restored and rebuilt to the highest standards, no expense spared" and then you read, "Pistons re-ringed" You can then judge how well the bike has been "restored" just by those few words.
OK a piston with no visible sign on the skirts of being run will I am sure be fine. In my opinion, Anything else should be turned upside down.
It's often cheaper to do it perfect in the first place!
Little example.
I just fitted 4 new Colsibro guides in my Scrambler head. I then reamed them all to make perfect. However! I have several sets of reamers for 5/16 guides and was doing exhausts slightly larger than inlets. Stupidly I picked up the exhaust reamer while doing one of the inlets. Now I "could" just let it be and it would "probably" be fine. But it would be so annoying if it were not. and it's so easy to do it now, (although highly irritating) It would just not be good practice to let it be! This is what I say about engine building or anything else, It is not a difficult job in itself, we all have hands and we can all physically do it. The hardest part is policing yourself to be a perfectionist! That is the only way you even get close to perfection.
Regards,
Julian "P" for pedantic *smile*
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Personally I do keep an eye out for NOS and low mileage pistons, particularly the genuine BSA 8:1 road rocket ones that are light.
race engines don't mind slightly greater piston clearances (but with good rings)
Sure anything well used suitable for reference or emergency only, but I would prefer a good lightly worn genuine BSA piston over a new JP any day. I greatly dislike heavy pistons (which many new ones are)
I also do not rush to regrind cranks (if within tolerances), I just fit new shells.
Depends on intent for use and extent of wear.
When I put my race engine together the bores and pistons were already used and it pulls over 7000, no smoke and good compression. I'm happy.
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Hi,
I personally take old pistons to cast new parts, because piston have an high part of silicium ... giving very good casting parameters....
Cheers Rudolf
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Clever little vegamite. ( oz slang saying for good)
Why not cast into new BSA pistons?
Cheers
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interesting answer to a question on a TV quiz
Q what is the most common element on Earth
A aluminium
I know certain cast aluminium has a good scrap price but takes a fair bit of it to count
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The most abundant element in the universe is hydrogen, which makes up about 3/4 of all matter! Helium makes up most of the remaining 25%. Oxygen is the third most abundant element in the universe. All of the other elements are relatively rare.
The chemical composition of the earth is quite a bit different from that of the universe. The most abundant element in the earth's crust is oxygen, making up 46.6% of the earth's mass. Silicon is the second most abundant element (27.7%), followed by aluminum (8.1%), iron (5.0%), calcium (3.6%), sodium (2.8%), potassium (2.6%). and magnesium (2.1%). These eight elements account for approximately 98.5% of the total mass of the earth's crust. Of course, the earth's crust is only the outer portion of the earth. Future research will tell us about the composition of the mantle and core.
Coppied from a good chemistry web site.
Julian
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Save them... put them up on your shelf... you may be famous one day... *eek*
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The most abundant element in the universe is hydrogen, which makes up about 3/4 of all matter! Helium makes up most of the remaining 25%. Oxygen is the third most abundant element in the universe.
Q what is the most common element on Earth
The question related to Earth however and they were wrong also according to Wikipedea
Aluminium is the third most abundant element (after oxygen and silicon), and the most abundant metal,
not that it is at all possible that I didn't hear the word "metal" *whistle*
We could start an element thread *fight*
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So the general view is to keep them if I want another dust gathering ornament (sorry don?t smoke so they won?t become ash trays) and that they should never see the inside of an engine again.
So will put them in a box at the very back of the roof space in the garage to become long forgotten. Then those that mentioned an emergency will also be satisfied, although I will probably forget they are there.
PS enjoyed the other banter *smile*
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I turn junk parts into trophys for the next bike show. Split'em in half makes 4. *smile*
Hate to think of the poor bloke in 40 years time that finds them to get his 100 year old A10 going. *sad2*
Cheers
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To play the Devil's advocate...
I say there is nothing wrong with using used parts. New parts and perfection is nice, but sometimes the pocket book won't support it and it can be amazing just how far used parts can get you, even the worn out ones. After all used parts are what get most of us to work every day.
As a bit of automotive racing trivia early in Micky Thompson's racing career he could not afford to buy matched sets of new pistons for his flathead V8 race motors. He bought a boring bar and scrounged up what ever used pistons he could find and frequently ran all different sized used pistons as that was all he could get.
I once put together a super rocket motor on a budget that consisted of no money to spend. The only new parts that went into it was a set of rings and a drive side oil seal. I put used high compression pistons in a freshly bored cylinder with 5 broken fins and I cut out a spacer to put between the barrel and the case to lower the compression.
I then took a worn out under-size timing bush and carefully scraped it out with a pocket knife and honed it with a wheel cylinder hone until it was a nice fit on my slightly worn standard crank.
Yeah, it was a remarkably half baked rebuild job. I figured it would hold together for a year and by that time I could afford to rebuild it right. 30K miles and 12 years later it's still running fine, has good compression and every time I've removed the timing cover I check the timing bushing for play and it's still tight!
Yeah...It's probably really due for a proper rebuild now but it still runs just fine with no funny noises so if it ain't broke don't fix it.
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There once was a clever bloke in NZ that melted down particular types of pistons to cast his new ones. I recall he had a rather quick Indian.
Cheers
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Anthony Hopkins? wink2 *smile* *smile*
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Not totally off topic but when RR made their 6.25 Liter V8 which latter on became 6.75 L , twin turbo fuel injected V8 they used wet sleeves and no 2 pistons are in fact the same size.
You have to either buy a piston & liner set or get a new piston custom made.
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as stated in this post it dpends on the size of your wallet and sometimes time restraints,i once blew the crown of a piston on my bike (triumph) the inlet rubber had split!! on my way to catch a ferry from harridge to the hook of holland i turned around limped home on one cylinder stripped the top end put in a used spare piston and caught the next ferry 9 hrs later the bike ran like that for a few years i was always skint then and not much better off now.......baz
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just rebuilding an Ariel square 4 motor , customer wants to use original standard size pistons. as bores are ok I thought re ringing would be ok, his request , the other square 4 motor Ive rebored and got new pistons for,
new rings arrived and after a struggle I find pistons wont go in bores . on checking the new GPM rings are ok for end gap but are 0.020" thicker on wall thickness , thus making them 0.040" bigger on outside diameter. now grooves have to be re machined.
I suppose A7 and A10 were more plentiful so spares are worth keeping and new rings would be the right size.
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Trouble is Chaz, when it all goes wrong the customer never says "well it's my fault for being a cheapskate, I should have let him do it properly" they always say "what are YOU going to do about it!" So a cheap job in reality means "will you pay for it please? I'm too tight"
I got fed up with trying to do things cheap for customers with more money than me and then getting kicked for trying to help them. It now gets done how "I" want it or they go somewhere else!
For your self it's ok if you want to take a risk, but for customers, Never!
Just my opinion based on my own experiences.
Julian
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My own experience re used bits is very positive . I bought a 54 s/a A10 which when started sounded like the proverbial bag of spanners , both mains completely shot and the crank ( small journal ) knackered . Being like most of us (who were around in the sixties ) at 17 I was always skint but had friends one of these found a plunger motor from a guy who we knew , He was adamant that the motor was a good 'en and I took his word and paid the princely amount of £5 plus some bits I had for a bubble car ( one of Willies finest ) I just had an idea that the plunger crank would drop right in same as barrels and pistons fingers crossed etc. I stripped and cleaned and even polished the doner bits and the s/a cases, fitted new big end shells, moved the d/side main from plunger cases to s/a and in my nivety simply transferred the main . The result was a motor that started 1 time after I'd oiled by kicking it with plugs out until it returned to the tank , idled wonderfully and then wouldn't break no matter what I did to it!! and remember stupid a 17 yr old can be. I've often thought about that rebuild and would like to think that the extra care preparing everything before reassembly outwayed the s/hand element of the bits. I also remember another slant on the R/R info about 2 posts back, when selling Ford cars a couple of years later a brand new Cortina wouldn't start, had to have the head lifted to sort it and every piston was a different size from standard to 40thou over all as sloppy as hell ,no compression worth speaking about ,selective assembly Ford called it ,you can imagine what we called it Regards BobH.
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I don't mean to say that using old pistons will never work, quite contrary, if they came out working fine then it stands to reason that they can go back in working, however to fit them to a new engine requires quite some messing and at the minimum new rings etc. So my point is why bother as the price of new pistons is so small. And the risk of a problem, especially with a customers engine where parameters come into play that you can not controll is so high!
Regards,
Julian
typed fast so excuse any spelling mistakes.
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wise words Julian, but I have tried to get him to buy new ones but does not want to go that way , and now Ive got 2 suppliers of oem standard piston rings he is happy.. will be a caveat on his bill
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Must say that I would love to see the SQ4 when it's running again. Extremely special motorcycles! I just swapped mine for a rather special Gold Star Scrambler. Finding out some really interesting race history about it now! Will fill the hole again shortly though ;) (as soon as the wife is not looking)
Julian
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Wouldn't dream of contradicting you Julian, to much respect for your engineering prowess ,simply giving an example and really possing a question ,did my motor turn out reasonably good simply because I was lucky or was it due to extra care I took, no meticulous care I took putting it back together? Also not put from any commercial point either , if I pay I want the best and I expect to pay well for the services of the guy doing a good job hence when I rebuilt my present motor I used SRM for all the engineering work and paid accordingly for a good job, didn't show the receipts to the wife though!! No back then in 1967 ( I was 17 ) I was simply risking about £10 and my time ,a completely different proposition than that of customer / engineer and of course it added to my knowledge and experience which in itself is priceless to an enquiring mind which fortunately I was blessed with, best wishes BobH. ps any new piccys of the project ?
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*smile* Don't worry about contradicting me, I can be as wrong as the next man and often more so ;)
You are absolutely right! It's not actually "What you put in" rather "The way that you put it in" an idiot can mess up even the best ingredients where as time, patience, knowlege and experience can make even the worst ingredients sing. However the cost in time goes up exponentially the worse the ingredients are, and this is what customers regularly fail to understand. Where as if we fail to understand that on our own jobs we usually pay the price as fuckitty fuck shit fuck fuck fuck! I will do that better next time ;o) We've all been there!
Julian
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I tend to say bugga a fair bit. *smile*
Cheers