Blew Top End Twice in 5 Hours, help.

[silvera3]

So I just purchased a 1998 Blaster off a buddy of mine and the first take we took it out, we blew the top end within 4 hours of riding. He said he hadn't done a top end rebuild since early 04' so we figured it was time for it to go anyways. Well, it was already bored .020 over and the only piston in town I could find was a .050 over so I had it bored to .050 over. I had the bike reassembled and took it out again for about 3 hours, just breaking it in and everything went great. Bike was running strong and sounded good. Well today we went out again and within 30 minutes of cruising, engine just shut off and I came to a sliding stop. We pulled the piston and compared it to the first piston and the grooves are in the exact same spot. What does this mean? Has anyone had any problems like this? Any input would be much appreciated.

 

[hotrodjrod]

looks like its running lean to me? Are the rings melted?

 

[silvera3]

No, pulled the rings off the first one and second piston still have them attached but can pull them apart. I am mixing 32:1.

-Spence

 

[newnick]

Looks like you didn't let it warm up enough.

 

[pittboss45]

Looks as if it is lean and or dirty air.

 

[Oldfart1stATV]

Yup

I'd check the carb and your mix. Looks like some burn and blow by. They are in the same place due to the same problem killing them both. Looks a bit hot to me. How did you break it in? That may be part of the problem, it's a sucky procedure and most folks don't do it at all or do it wrong. Looks like some sh*t got burnt on top of the piston on the right, so like PB said see if you are sucking dirt, too.

A

 

[silvera3]

As far as break in goes, I was light on the motor for about a half tank ( 2 hours ) And then I started to ride normal. Could the carb be causing this. It has an after market carb on it. Also, the air filter is a cone style that sits right behind the carb ( not in the airbox ) But I do regular cleaning on the filter every other ride. :"> Do air cooled motors flex more with heat than say a liquid cooled motor? I don't tend to let this warm up a whole lot, but never had any issues with my liquid cooled motors, I just let them warm up for a few minute or so.

 

[dirtyblaster]

wait,did u get a good bore when u went from .20 to .50 was it done professionally? what are the mods? if you have a 240 kit u are required to run race fuel. let us know. what kind of oil are u running?

 

[Stryder917]

check your jetting, maybe you should do an official breakin process http://www.blasterforum.com/do-yourself/315-how-break-two-stroke.html

so yeah.. do this, and make sure that you got it bored correctly when you got it bored out for the rebuild

 

[blaster551]

do you have a bent rob meby its pushing it to the left or right to much

 

[bacardiboy]

Do you still have the oil injection system hooked up? Is it working correctly or at all? Saw an article on how to check it out(test it) somewhere...thought it was on here...

 

[Tim Steele]

You need to heat cycle for the 1st couple of outings and let the motor cool off completely before you ride it again. Proper breakin = long engine life. Let set overnight retorque the head and then gradually load the motor. No staedy state throttle settings up and down on the gas acccelerate and let off to seat the rings,brief throttle bursts after the 1st couple of heat cycles ,use good oil ...Jetting too lean ,timing advanced and or a lean fuel mixture may be a facor in the premature demise as well.

 

[silvera3]

I pre-mix everything 32:1, the oil pump seized once and cause my first top-end going south and at that point I removed it and just pre-mixed it myself. After breaking everything down we found the bike had never been jetted, still the stock 230 nozzle was in there so were thinking, just as everyone has pretty much said, it leaned out and blew.

-Spence