locked up

[Austin77]

my son rides a 06 kx 100. We were at the track praticing Sunday and the motor locked up. There was no signs at all of this about to happen. He told me that the bike was running strong as ever and then, as he was about to jump a table top it locked up. When he first pulled it to the side I could not turn the engine but I didnt use alot of force. After the it cooled and contracted I was able to turn it a couple of times I wanted to here and feel how ruff it was " maybe a dum move" it was ruff feeling. A guy at the track seems to think that my piston skirt broke off. And That i might just have to buy a pistion and they usual stuff to rebuild to top end. The man that I bought it from said it had 10 hrs on the top end. My son has put, at least 10 more hrs on it. Can anyone give me some ideas on what may have happen and what kind of bill Im looking at? Thanks for youlls help

Oh buy the way I amsoil at 40 : 1

 

[Chili]

No way to tell until you open it up. It may be a busted up skirt or a classic 4 corner seizure. No way to estimate the bill until you know what damage you need to repair.

 

[Austin77]

Thanks for the reply

 

[rmc_olderthandirt]

Sounds like a typical engine seize. They tend to be running at their best right up the seize. Why? Because when you are pushing them the hardest is when the cylinder temps get the hottest.

No doubt about it, you need to tear the top end apart. About an hours work will get you to the point where you can see how bad it is.

I am guessing new piston and cylinder re-plating.

I wouldn't have expected a seize with only 20 hours on the engine but some manufactures recommend refreshing the top end every 15 hours. Sounds like it seized just before the jump, which is a lot better than having it seize just as he gets airborne! Having the rear wheel lock up mid flight can make for a nasty landing.....

Rod

 

[Bigdogdaddy69]

Ive had a piston skirt like stated above come apart. When My piston broke on my rm 250 some how it did not leave a mark on my cylinder, I guess i shut it off in time, I was also running amsoil. Im not sure if it happens every time a piston breaks but my bike made a loud popping noise and it almost blew my pipe off. Good luck and get your son riding again.

 

[2-Strokes 4-ever]

Perhaps the "only 10 hours" stated by the seller was a stretch. My older son was our districts MX champ when on an 80, and he ran them real hard (melted a plastic waterpump impeller more than once.) Our routine then was... piston every 30 hours with a ring job at 15. Very important to warm up a motor too before riding because a still cool cylinder (coolant in it) has not expanded enough to allow room for a hot, expanding piston (seizure for sure).

 

[Austin77]

thanks for the replys will up date after I tear it down, have to get a Olifens unit up first, Thanks to IKE