Author Topic: Pistons  (Read 627 times)

Offline wardleybob

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Pistons
« on: 01.01. 2014 14:26 »
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

Offline Dean

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Re: Pistons
« Reply #1 on: 01.01. 2014 17:01 »
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?
Never tell people your troubles. Half of them are not interested and the other half are glad you're getting what's coming to you.

Online Triton Thrasher

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Re: Pistons
« Reply #2 on: 01.01. 2014 20:59 »
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."

Online trevinoz

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Re: Pistons
« Reply #3 on: 02.01. 2014 19:53 »
I'm with you, TT.
Solid skirt clearance is 0.004" - 0.0055".
I have mine with 0.005" clearance.

Trev.

Online Triton Thrasher

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Re: Pistons
« Reply #4 on: 02.01. 2014 22:16 »
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.