Bike blew up, wrong jetting ?

[MCEWEN]

Hey I'm having a hard time getting the jetting set properly on my 03 blaster.

I recently just installed a full fmf pipe and a boyesen rad valve. Jumped the jetting up to a 290 with the air box cover on. Air screw 1.5 turns out. The temp was about -5c. I took it out for half an hour or so today and it was running better than it ever has then out of no where shut off and locked up...took the top end off and found one half of the piston skirt broken off. Is this because it was running too lean ?

 

[best]

Nope.
It was because it was running better than it ever has and the piston was getting loose in the bore and fatigued. The rpm and stress finally broke it.

You can teach an old dog new tricks but old motors need a new piston first.

 

[Tooloose]

Recently many riders have came to the shop with blown up or seized top ends. We have came to the conclusion that the alcohol enriched gas and two strokes do not mix! Even worse, worn out rings let compression slip by generating extremely high temps and mix that with 10% alcohol enriched gasoline bam-boom,bursted piston skirt, seized engine. Buy premium pure gas to mix with, for all 2 stroke engines! Nothing less!

 

[Tooloose]

Also leak down check all 2 stroke engines periodically Air leaks SUCK Right?