The Triumph Dolomite Club - Discussion Forum

What size is this Sprint piston?

Look's like standard to me

Tony.

It says Std, but at 90.28 is it 20 thou (of a mm) undersized ??? One to measure I think!

xvivalve wrote: ↑Mon Apr 02, 2018 6:34 pm It says Std, but at 90.28 is it 20 thou (of a mm) undersized ??? One to measure I think!

I was thinking it is std but looking at the figure below (0.02). It won't be 20 thou of a mm. though. It is 90.28mm. across the skirt of the piston.

Hi Mart, You probably know most of this already, but page 12-5 of the Sprint Workshop Manual gives the various dimensions of the Sprint standard pistons. And the piston lower skirt dimension is given as 90.277mm to 90.290mm for Grade "G"std . So that agrees with what you have measured as 90.28mm. A STD size grade G piston.
As to what the 020 number refers to ... sorry I don't know.
My initial thought it was a mixed metric ( 90.28mm) and imperial measurement (+0.020 thou ) ???

Tony.

I would say the 90.28 is the skirt size and the bore clearance is the 0.02mm (not thou), so needs a bore of 90.3mm which is standard

Tony

Thanks guys. Yes Tony G, that makes sense. Ah! well, off to the M/C shop tomorrow.

What brand are they Mart?

Tony