rebore piston clearance

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paulvk
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rebore piston clearance

Post by paulvk »

Rebore piston clearance ? I have a Ajs 500 twin M20 and want to rebore my standard barrels to +20.
I have a pair of BHE or (BHC) Split wire wound pistons . Like to know the clearance for threes.
Regards....Paul
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ajscomboman
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Re: rebore piston clearance

Post by ajscomboman »

Sounds like you have original BHB pistons. They were designed to run very close tolerances around 1.5 thou off the top of my head however others may chime in with a definitive later. There maybe some specs to be found in the archives google archives.jampot.dk
paulvk
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Re: rebore piston clearance

Post by paulvk »

thanks for that. Yes they're BHB, these pistons have lots of numbers on them. Apart from +20 they have 022669 ,W151,L60.
No idea what they're for..
Cheers.. Paul
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GSAX1
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Re: rebore piston clearance

Post by GSAX1 »

I installed mine with a clearance of 0.03 mm / 0.0012". No problems and no tightness. F.W. Neill says in his book that clearance on the wire-wound pistons for the 500 twins was 0.0009" when new.
paulvk
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Re: rebore piston clearance

Post by paulvk »

Wow... Thank you. That is close.. Is that overall or per inch of piston.
Regards.... Paul
g80csp11
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Re: rebore piston clearance

Post by g80csp11 »

if you look at the user manual for 51 G9 twin it gives piston diameter measurements of 2.5984" on standard at bottom of skirt and , bore of 2.6" that would give .0016" clearance, so provided you have wire wound pistons then this is what you should aim for .

http://archives.jampot.dk/book/Owners_m ... Manual.pdf
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GSAX1
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Re: rebore piston clearance

Post by GSAX1 »

paulvk wrote: Fri Nov 26, 2021 6:36 pm Wow... Thank you. That is close.. Is that overall or per inch of piston.
Regards.... Paul
I had my cylinders honed to an overall clearance of 0.03 mm / 0.0012". Yes, that is close :) .
paulvk
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Re: rebore piston clearance

Post by paulvk »

OK once again thanks.
Cheers
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