melted the exhaust side of the piston, help

[yamaha_blaster03]

hey guys i was out on the ice today practicing for ice racing and i noticed i was in 4th gear and i lost some power and then 2 minutes later it died. I couldent get it kicked over again so i took the top end apart and i saw the exhaust side of the piston was melted, i have no idea what some of the causes would be, i know i need a new top-end but can anyone help me on the causes?

 

[gonzo]

lower the clip 2 notches and go up about 5 on the main or put the air cleaner lid back on

 

[Blasterb0y794]

How long were you running it for? Were you red lining it alot, and were the tires spinning alot? If you were red lining it that could have been the cause for the melted piston

 

[yamaha_blaster03]

i was riding for around 30 minutes and i wasnt going all out on the track at the time, could it be that i got some snow in the carb?

 

[89custom]

did you rejet for winter ridding?

 

[yamaha_blaster03]

yes its a .280

 

[pittboss45]

Too small

 

[89custom]

shizam. theres your cause.

 

[yamaha_blaster03]

i ran it last year like that too... so idk whats up

 

[gonzo]

bottom line is you cooked it, last year you may have been on the edge and got away with it this year its 10 degrees colder not as much humidity and oops there goes the piston, it happens, make it so rich it blubbers and then back it down, I see where people say jets are expensive, no there not pistons and bore jobs are expensive