Engine blown!

Hey today me and my buddy were riding and he was on my RM 125. and he said all of a sudden it died and wouldn't start. We had been riding for a while the bike was running fine but I guess it was just a bit too cold outside and it was too lean becasue the plugs were white. So i tried kicking it over and it had no compression. But it was still kicking over okay so i figured that was a good thing. But right before i was about to pull the head off i was pushing it over with my hand and feeling the compression and the piston got stuck!!! (but i stoped right away - didn't hit it or push hard)

So i pulled the head off and the piston is stuck about half way down and the top of the piston looks a little melted - the head and what i can see of the cylinder walls look okay though.  My next step is to pull the jug off an pray its not stuck to bad. But I wanted to get some insight because this will be my first rebuild.

What would you guys do next?

What should I look for in cylinder and the ports?

And from what I told you do you think it sounds bad? I'm hoping its just the piston and rings.


Any other advice would be great before I screw anything else up.






I would start by cleaning and inspecting the bore and head to make sure everything is still good to go. Then I would figure out why it was running lean before you put it back together. 

Yah, I think it was a combination of cold weather and maybe cheap oil and to lean of a mixture. I always use Ipone but cheaped out and bought a bottle of AMS oil and it blew up.

Usually mix 40:1 but maybe should go to 32:1

Ask your buddy if he held it wide open before it blew up. That could make it lean. Not dumping enough gas at that rpm. Mic. The cylinder before u buy a piston. To make sure the cylinder is straight. If u don't no how to mic. Or have gauges take it to a machine shop

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now