86 trx250r popped piston HELP!!!

[01modblaster]

[IMG][/IMG] Hi I need as much help as I can get, I have a trx250r and this is whats done to it
5mm long rod (hot rods)
67.5mm bore
V Force3 reeds
Reed spacer
K&N air cleaner
FMF Fatty glod series
FMF power core silencer

Stock carb the jetting seems ok neverdone a plug chop and never had a LEAN plug always loaded if anything, Could the carb be too small and cause this, and I am @ 180psi before starting it from new bore. I ran premium pump gas! should I have ran race gas?

[mgty3whlr]

Did you melt the piston??? When did it happen? were you running it full thottle for a long period of time? need a little more info about your riding habits, when was it rebuilt?

[01modblaster]

I was running in sixth gear, the piston melted right at the plug, not a lot of damage beside that hole. I rode the quad alot 3-4 times a week for 1-3 hours @ a time never had a prob. don't know when last rebuild was.

[01modblaster]

but when I ran it before that trip never really ran that long at that speed

[01modblaster]

could it be to small of a carb?

[mgty3whlr]

Unfortunately, unless you jet the carb on the rich side, you'll melt pistons all day long running in 6th gear, wide open.

[BlueDiablo]

Big ouch man. Always keep that piston to remind ya of your mistakes. lol

[SHOWED UP]

my 86 trx did the same thing. it is from running lean.if you look at the front of the piston you will have some scaring. this is where being ran lean really effects the piston. I was in 5th for a period of time my bike started to bog by then it was to late. what happens is in taller gears you have plenty of air but the engine is not able to burn the fuel like it is when going through gears and powerbands. burning holes in the top of your piston in most cases happens because a constant high speed in tall gears stresses the motor to keep puttin out ,then bog and BOOM. I think your carb is fine you have riddin it many times with no problems. rebuild your bike and remember this.

[01modblaster]

would a ricky stator help, or the CR250R electrical sys.

[ky 2stroker]

I dont think the stock carb caused that to happen, but I'd say a larger carb would only help power on your 250r. probably the best bang for your buck would be to get a keihin 38mm air stryker carb for about $200. it helps the power everywhere and the more mods you get, like porting especially, the better it works. and an aftermarket ignition like a cr250 ignition is suppose to really help the powerband also