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broken piston skirts on 2 smokes

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seems to me that as the bore wears the piston begins rattling in the bore and when severe enough the skirt grabs (snags) a port and snaps off.

what amazes me is how the boken piece of the skirt ends up on top of the piston and beats the hell out of the combustion chamber, as evidenced by the hammering marks.

Even more amazing is that it does not enter the crankcase.

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seems to me that as the bore wears the piston begins rattling in the bore and when severe enough the skirt grabs (snags) a port and snaps off.

what amazes me is how the boken piece of the skirt ends up on top of the piston and beats the hell out of the combustion chamber, as evidenced by the hammering marks.

Even more amazing is that it does not enter the crankcase.

Must of got lucky on your cases,one of the rebuilds i did this year took out the bottom of a case too.:banghead:It was UGLY! For his wallet...

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skirts can crack just from fatigue of time, or running loose in the bore. whats alwys impressed me is how much ends up in the pipe, and how people never think to clean the pipe out.

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Many years ago my tm400 seized I removed the head and collected numerous pieces of metal not knowing where they came from until I removed the barrel it was the inlet side skirt of the piston incredible how it travels up through the ports then wedges the piston and doesn't end up in the crankcase.

Regards Rod.:busted:

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My hypothesis was based on the 77 PE250 I just picked up, seemingly nothing else wrong with the motor, simply the piston skirt broke. Motor looks to be in nice overall shape, not even really dirty, paint intact, bike shows signs of care from over the years, I think she just got tired. New wiseco piston and a fresh bore should fix er right up.

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of concern with an older twostroke is the crank end seals, get dry and hard and can suck air, somehting to watch for

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of concern with an older twostroke is the crank end seals, get dry and hard and can suck air, somehting to watch for

I agree! So far I have had great LUCK with em, and not replaced a crank seal yet. Friend of mine, says the older two strokes don't make as much pressure in the bottom end as newer ones and seals not a big factor, and even if they are leaking a wee bit you won't know it.... I dunno...

I know I much prefer a two stroke top end rebuild to a 4 stroke. :busted:

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used to soak old seals in a product made for auto transmissions called "seal swell" , know guys that even used brake fluid

depending which motors I find its as much work to futs around with the power valve mechanisms as it is cam and cam chain on a 4s

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