The BSA A7-A10 Forum
Bikes, Pictures, Stories & more => Wanted & For Sale => Topic started by: BSARoadRocket on 14.06. 2022 05:32
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Hello all,
I would like to find some .070 or larger oversize A10 pistons. I prefer flat top 7.25:1 or even the dished top 6.5:1 pistons. Years ago I found some NOS hepolite 6.5:1 dished top pistons that came from a seller in Malaysia in .070 and .080 over so I know they existed but I have yet to find any more.
I know conventional wisdom says not to bore A10 cylinders beyond .060 but, I believe that with a good even casting even .100 over could be done with out problems.
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I know conventional wisdom says not to bore A10 cylinders beyond .060 but, I believe that with a good even casting even .100 over could be done with out problems.
In my view - for what it's worth - there'd be so little cylinder thickness left below the flange that it could break off or, even worse, the cylinders could part from the flange. My cylinders are at .060 and there ain't much left.
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I've looked over and compared a lot of cylinders. I have one that was machined off from the factory so the front of the right sleeve is too thin and the rear of the left sleeve is too thin and it could barely take .040. I have another small fin thin flange cylinder that is bored to .080 with high compression pistons and it obviously has had a lot of use that way with no problems. I know of somebody else who ran an A10 at Bonneville with a thick flange cylinder and custom high compression .080 pistons and never had any problems. I think the key to avoiding having a cylinder crack above the flange is making sure the base nuts are tight. I know the thick flange cylinder is ideal but I think the thin flange cylinder is still adequate for regular street riding.