Burris Piston Failure

[David Luciani]

gordon g's theory is what steve was postulating about the pin being battered by the ring movement.
i've forgotten most of what he wrote and wil be revisiting that book again as it has alot of info that is useful.
of course alot of it is way too much for what we're supposed to be doing but it is still fun to read.

[Scott Kneisel]

Hey Scott,
I'm sure everyone is tired of me quoting The Two-Stroke Tuner's Handbook... I know, I know, I gotta widen my horizons... 

Anyway, on page 24 and the top of page 25, Gordon Jennings describes his theory for how this can happen.
See what you think.  Did these motors have work done on the exhaust ports?
Doug

http://www.vintagesleds.com/library/manu...ndbook.pdf

Thanks, this is good reading and makes a lot of sense.
The Mc91B has stock exhaust ports but the 101 (first gen) with a divided exhaust port has had both ports raised and slightly widened at the top of the outside corners. They are not fully eye browed but are widened a bit. I suppose this could add to a pin problem but the port is not nearly as wide as the 101A and on up with the oval port.

I seem to have at least one of these pin failures a year in the last couple years. Now that I am building mostly for myself, I hope this calms down.
Thanks again, Scott