Need '77 250 Specs

[Bob]

Can someone tell me if 71mm is standard bore for a 1977 Penton 250 ?

Is 71.25 first over ?

What is the piston-to-cylinder clearance and ring end gap ?

Thanks,
Bob in Va

[tofriedel]

Bob,

71mm is the correct std. bore.  The piston clearance is .050-.070mm for the 250.
The piston ring end gap is .15-.20mm

Tony

 

[Larry Perkins]

To the best of my knowledge 71.25 is like a half size over and were made by Wiseco.  The Mahle KTM pistons I believe were 71mm, 71.50mm, 72mm, and 72.5mm.  That is my memory.

 

[Bob]

Thanks guys.

Larry I have an original KTM / Elko piston which is 71.25. The part number is 543 30 007 201. I hope this is correct for my '77 250