Author Topic: pistons and rings  (Read 2313 times)

Online bsa-bill

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Re: pistons and rings
« Reply #15 on: 18.04. 2012 09:57 »
but the socks i buy nowdays are very tight round the ankles has any one else noticed

I haven't noticed that Tumbleweed  but guys watch out for tight garter elestic, the thought brings tears............................
All the best - Bill
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1959 Rocket Gold Flash - blinged and tarted up  would have seizure if taken to  Tesco

Offline duTch

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Re: pistons and rings
« Reply #16 on: 18.04. 2012 13:20 »
Yeah chuckle at all that stuff, but serious, Tumbleweeds, if your bore is an even 70mm, you may get away lucky with just hunting up some standard bore pistons,and no rebore??
       Good luck ,duTch

Oh yeah, I'm not even going to think about suggesting sleeving the pistons *warn* *eek*
Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
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Online RichardL

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Re: pistons and rings
« Reply #17 on: 18.04. 2012 15:37 »

Beezermacc clearly knows his stuff, no debate there. Knowledge of the numbers and markings inside the pistons is foreign to me and, I'd guess, to most. The problem I'm reading into this discussion is that, with your measurement method and accuracy, it is really impossible to give good advice. Using your flat ruler or scale, you've managed to correctly measure the bore diameters to within 1 mm. Not too bad, accuracy-wise, with what you have. But for the pistons you are off by over 2 mm using the same method across flat-top or dished pistons, per Beezermacc (meaning, no dome to go over).

The only reason I'm pointing these things out is that you appear to have now leapt to a decision to rebore and get new pistons. In my opinion (which, with the addition of 1-1/2 quid will get you a cup of coffee at Starbucks), you should get some really good measurements before making that leap. Of course, your machinist will provide that info when you go for the bore, but by that point you've probably committed yourself. At 40-over on the pistons, if the fit is actually right, you would not want to go up to 60 over, not just for the money, but because it is the last practical rebore value. Having spewed all that, my guess would be that your pistons are too loose in the bores, but it should be validated with good measurements.

Richard L.
Plan on signing up for the world-wide 2020 DISTINGUISHED GENTLEMAN'S RIDEon September 27, 2020. This year it's a solo or pillion ride in dapper attire. Watch website at for details.

Offline Tumbleweed

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Re: pistons and rings
« Reply #18 on: 18.04. 2012 21:02 »
thanks everybody for your time and advice, i took my barrels and pistons as suggested  to an engineering company. with the right measuring gear. my pistons were badly worn in the grooves, when you see them along side of new ones you can see how bad they are, so i think i had better have a rebore and new pistons and rings , they will supply the piston set or i can get my own, the rebore was very reasonable pricewise, its just a matter of getting the piston set at the right price,     once again chaps thanks.
Semper in excretia sumus solum profundum veriat.

Online Triton Thrasher

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Re: pistons and rings
« Reply #19 on: 18.04. 2012 21:08 »
Do not accept a rebore tighter than has been recommended in this thread, or siezure is very likely.