Pistons

[wardleybob]

Hy merry christmas has any one had problems with Wassels (he polite ) pistons .I have only done 200mls
And the left one has picket up. It was bored with 4thou clearance . Wardley bob

[Dean]

Hi Bob
last summer my left piston picked up. Its always the left isn't it!
My pistons weren't Hepolites (GPM). I guessed it was a lube issue but a strip down showed all was Ok with lube. But I still went for new pump, pressure relase valve, and oil filter so I could run modern oils. Perhaps the rich running in the early days after rebuild washed oil off cylinder adding to the inherent lubrication issue on ledt cylinder?

[Triton Thrasher]

4 thou clearance is tightish on a 70mm bore.

Any suspicion of a weak mixture, or timing off, or even just slogging in too high a gear would sieze it.

Avoid barking up wrong trees like "bad pistons."

[trevinoz]

I'm with you, TT.
Solid skirt clearance is 0.004" - 0.0055".
I have mine with 0.005" clearance.

Trev.

[Triton Thrasher]

I'm with you, TT.
Solid skirt clearance is 0.004" - 0.0055".
I have mine with 0.005" clearance.

Trev.

Thanks, I didn't know the exact spec.

If 0.004" is minimum, you're on thin ice if the clearance is less than that at any part of the bore. And there are inaccuracies in boring and honing, which have to be allowed for.