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Piston Clearance

Big Sid

There are long feeler gauges for this . Place the piston half way or more down the bore , not up top , a 4 thou . strip down between the skirt and the bore on the front or rear thrust face , not inline with the piston pin bore . If its a fairly firm tug to slide the strip out with a 4 it's usable . Tighter can often nip up , looser will give rise to slap . Many go much closer , down to 2 but it's very prone to pick up or seize in the bore if not broken in VERY gently . Not for us . My thoughts anyway . Sid .


Well Known and Active Forum Website User
VOC Member

I have always used a micrometer and a telescoping gauge. It is much easier to measure in different spots to find tapers and/or ovals.


Big Sid

Absolutely the best and the way Bill Jean in his superb shop would do it , but very expensive to purchase . Not what was requested or needed for an easy check . The original owner of his Vincent would do it as I described as most back then did . I was there .
The original muff assembly by now is a poor thing anyway , a loose fit when hot having lost most of its interference fit and there are pockets of burnt oil up between in many places so cool very poorly if run at any real speed . And will easily seize its piston . Modern replacement cylinders are far better from the best machinests and cool far more effectively . No comparison . Sid .
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