blew up the motor 2 times, whats wrong?

[mineralgrey01gt]

My brother blew the motor up twice on 250r and the first time it straight tore up the cylinder and piston. Ive never seen something so scarred up in my life.

Well I gave him the motor off of mine since I busted the case on it and he took the top end off and put it on his motor and he said it ran like a champ and today it blew up again. He pulled it down and its scarred in the same exact place.

Also he said that the plug is a gray color. What do yall think is wrong with that thing? He didnt put new rings in it when he swapped top ends if that matters (which I thought it would)

[EXtreme-]

you probly have aluminum in your main's, which are now trash from the first blow and your rod is probly shot and needs replaced. You need to take it to a reliable mechanic and start over.

[mineralgrey01gt]

thanks a lot. I never thought about that. Ill let him know about it

[RedRider23]

thats exactly what my r motor did. and i found out that my water pump bearing was stuck, definelty check it before u redo it again. my oil was a silver blue color.

[mineralgrey01gt]

now hes telling me every time he shifts it that he is revving the hell out of it. Sounds like to me it overheated both times from him revving it so high on almost every shift. I noticed that the other day when i watched him ride it that the bike would rev as high as it could go each time he shifts it and downshifts it

[beobe99]

I was going to say it might be your bro and nothing else..

But of course check your jets, and water pump.

Also check your plug cap (I could be wrong with this cause its only something Ive heard) If your plug cap isnt tight like say theres a space between the top of the plug and the metal contact it will create a bridge/arch will will give a much hotter spark.. maybe to hot..

BUT dont quote me on that please haha! I do think i remember you having an issue with the plug/coil cap before.

[mineralgrey01gt]

i think its him lol. I told him when I get my new motor hes not riding mine!!!! lol

[86 Quad R]

it sounds like a combination of things thats causing the failures. its very important to make sure that there arent any trash in the bottom after an engine failure and unfortunately this involves splitting the cases and from what you stated it sounds like he has a lean condition aswell.

[fireburns99]

Sounds like a lean condition possibly causing the initial problem, and then left over crap in the bottom end that destroyed the second.

If all is set up right, revving it to the rev limiter shouldn't matter.

[250r4life]

Originally posted by fireburns99


If all is set up right, revving it to the rev limiter shouldn't matter.

exactly... is there any other way to ride a 2 stroke besides revving out each gear? :huh

[mineralgrey01gt]

hmm, ok thanks yall. How do you fix a lean condition? I know its a stupid question but I really dont know and I need to figure it out since mine will be going shortly. Also the mix he runs is 32:1 with Maxima Super M oil

[wilkin250r]

Can you get a picture of the piston? If it's the same problem, same spot, it sounds like it might be a lean seizure.

A lean condition is caused by jetting, not enough fuel. But it's not always as simple as "a larger main jet", or simple plug color. The carburetor has more adjustments than just a main jet, and you need to test all those different circuits and throttle positions they affect.

It's possible to be lean at 1/2 throttle, but rich at full throttle. Pulling the plug after riding all day won't tell you which area is rich or lean.

[86 Quad R]

good READING (http://www.duncanracing.com/techfaq/Tech_keihin-carburetion-jetting.phtml)

[mineralgrey01gt]

thanks for the info!