97 rm125 siezed/weird sound?

The other day, we were riding my buddies rm125 around in the field. We had just replaced the piston and rings. After riding it, we let it sit for a few days, as there was a rain storm. Today, we went to start it. As my friend kicked the starter, it made a sound that is different from usual, which is a sort of metal-on-metal sound, and didn't even attempt to start. After kicking it for a few more seconds, not thinking anything was really wrong, the kickstart siezed and would not budge. The only way to get it to move is to put the bike in gear, pull it back as hard as possible, so that the back tire moves a little, and then try kicking it again. However, it usually siezes after 1 or 2 kicks again. I really have no idea what it might be except something to do with the crank. Unless the piston turned sideways and siezed somehow haha... HELP!

Sounds like it's time to look inside. If it kicks once or twice after you pull it backwards to free it, I doubt it's the crank. That would seize each time you tried to kick it at the same spot. Take the clutch side case cover off and look for "spare parts" floating around inside that may be jamming. With the bike in neutral, remove the stator cover and try to turn the motor.(remove spark plug to make it easier) If it doesn't turn, pull the clutch off and check again. That will eliminate or prove it's the crank or piston.

This actually just happened to my nephew's 1997 RM125 Sunday evening. I tore it down yesterday and one (maybe both) of the crank main bearings are seized. I am waiting for the proper flywheel puller because I don't have the right size here. But the cylinder, piston, and rod big end bearings are all in great shape. This bike was rebuilt a few months before we bought it, but I now suspect they reused the old crank bearings.

I also think it could be the crank bearings

here's my crackpot theory: when it's getting "stuck" that's where the bearing is damaged. Breaking it free removes it from that damaged spot, then kicking it over again gets it back in that damaged spot and gets it stuck again

time to tear down and start thinning out the wallet..

Assuming it was running when it was torn down to do top end, I seriously doubt the crank has seized while it was sitting for a few days. If all else is the same, and the only thing changed was the top end, therein lies your problem. Take the top end back apart. Perhaps a ring was not seated properly, or a circlip has come out. And for gods sake, stop trying to kick start it!! The first "metal on metal" noise should have been your queue to take it back apart.

thanks for responding guys, I'm going to take it apart and see whats up

Since this thread already exists I am just going to post here.

On my nephew's 1997 is definitely the crank bearing that seized. I got the cases split today and the stator side is seized. My problem now is I can't get the case half off that side of the crank. Considering you can only buy a $500 OEM crank and not an after market one I need to be very careful I don't ruin the crank trying to get it out of the case. Normally I would just press it out because I would be replacing the crank. In this case I only plan to rebuild the crank since it's apart. So I don't want to bugger up the thread end and screw myself.

Just figured I would update so the OP or anyone else would have the info for future reference.

that's what was happening to my cr80 before I put it together turned out there was a shard from the piston stuck in the crank barring lubrication hole causing it to seize, than when I would back it off it works for a wile than it gets tuck again.it kinda scared me for a moment cause I couldn't figure out what was causing it.

Since this thread already exists I am just going to post here.

On my nephew's 1997 is definitely the crank bearing that seized. I got the cases split today and the stator side is seized. My problem now is I can't get the case half off that side of the crank. Considering you can only buy a $500 OEM crank and not an after market one I need to be very careful I don't ruin the crank trying to get it out of the case. Normally I would just press it out because I would be replacing the crank. In this case I only plan to rebuild the crank since it's apart. So I don't want to bugger up the thread end and screw myself.

Just figured I would update so the OP or anyone else would have the info for future reference.

Why cant you get the case off? Use a little heat on the case and the bearing should just about fall out. Be care full to try to heat evenly to not crack the case.

I just did that and was able to get the crank out. If you look at 3 o'clock and 7o'clock you can see where the race is damaged around the bearing. The cylinder and piston are in great shape, the lower rod bearing is intact. I am not sure what caused this other than the bearing just failed or the previous owner said it had a fresh rebuild before we bought it and maybe some shrapnel got down there and they didn't bother to split the cases to find it/get it out.

RM125-8.jpg

Edited by AdvCoop

Sorry. I thought that the case was stuck on the crank yet. Try heating the bearing race real good and it may fall off with a few taps on a block of wood. (Be sure to wear thick gloves!) Or if you have a puller when it's heated. Or , last resort, air cut off tool very careful. Cut the outer race and remove bearings then work on inner race. Very carefully get it as close the the crank as possible. Even if you bump the crank slightly, it shouldn't make a difference, heat it up and it should pry off real easy.

No you were right, it was the case stuck to the crank i was having trouble with. That picture was after using heat to get the crank out, the bearing came out with the crank (typical, no biggie). I have to get a parts order together (plus the cash to order it lol) and then give everything a very good cleaning so I have some time to get that bearing off the crank :thumbsup: .

I am in need of help, and as quick as possible. How the **** do you get the cylinder off. I see three bolts, but shouldn't there be four? wheres the other one! thanks

is there a power valve? if so it's behind the cover

is there a power valve? if so it's behind the cover
The 4th is behind the power valve cover.

like they said, it's behind the cover on the right side of the engine. You will also have to disconnect the power valve linkage rod thingymajigger thats under that cover also. Here is a pic for you to check out. It's the same year and everything. If you got anymore problems or questions, feel free to ask.

100_3147.jpg100_3149.jpg

Edited by aaronjohn20

ah, thanks. i can't believe i didn't think of that before. changed my piston and rings, but now the bike sounds different for some reason :smirk: hope there's nothing wrong with it maybe an exhaust leak

There is an o-ring on the end of the exhaust where it slides into the cylinder. That might be damaged or missing, and explain the different sound. It will also cause power loss if not sealed properly.

Just a thought, but did you happen to put the piston in backwards? I'm not sure if that would make a different sound or not. Also like Jethro said, there maybe something up with your exhaust oring. You should never reuse those.

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