Rm 125, 2002 problems (crankshaft)

[rosehill_rider]

After a small drag strip my rm started making a knocking/clicking noise in the engine. A couple seconds after i heard it the engine seized up and the back wheel locked up. I got it home and took the top end apart. The piston and cylinder were fine. The connecting rod is locked onto the crank shaft and has no up and down movement. the crankshaft still spins freely though. Being new to working on bikes i'm not to sure of what the problem is. I would guess that the bearing between the crankshaft and connecting rod is busted and preventing the connecting rod from moving up and down. (It seems like the connecting rod and the crankshaft are one piece and move together util the connecting rod hits the cylinder walls) Any idea what the problem might be? Before i dive into the bottom end i wanna have an idea of what to look for.

Thanks for any advice or help you can offer.

 

[TRexRacing]

Sounds like ya pushed it just a bit too far and the big end rod bearing has seized and killed the crankshaft.Time for a new one.

 

[rosehill_rider]

what all needs to be replaced

 

[Rich Rohrich]

what all needs to be replaced

Until you take it apart and inspect it, no one can know.

 

[rosehill_rider]

ok thanks for the help. if it happens to be just the big end rod bearing that has seized it is possible just to replace the rod and not the whole crankshaft?

 

[gregorious77]

Yes but you will need to have it done by a shop so the 2 crank halfs are aligned correctly

 

[whenfoxforks-ruled]

A basic rebuild, new crank, bearings and top end with gaskets, around 300 dollars. I would have a professional check, hone the cylinder. I like Forward Motion for that, and if the rod needs to be pressed. Some wiseco does not stock? He is in good with wiseco by the way. Them or hot rods should offer complete engine rebuild kits.

 

[rosehill_rider]

thanks for the info. Would anyone happen to know how much just the labor would cost for this type of job. I bought the bike for 1400 and 300 dollars for a complete rebuild is gonna hurt enough. Is it really worth all the money if the repair cost is a third the value of the bike?

 

[Rich Rohrich]

If you have someone else do the work you'll have to tack on another $300-$400 in labor in addition to the cost of the parts.

 

[whenfoxforks-ruled]

If the bike is worth 1400, its only worth it running.

 

[rosehill_rider]

I've decided i'm gonna try to do it myself. We have all the tools to check the cylinder. I'm hoping the only broken part is the big end rod bearing. I'll have a professional align the crank assembly if thats the only problem. Thanks for the post. they help alot.

 

[qwert321]

If you are going to get somebody to put in new rod you might as well just buy a hot rod crank.dont think it would be that much more if not cheaper crank is $183 at rockymountain rod is $92.I would go with crank personally but not sure what a shop will charge you to put rod in and you have to hope its not the rookies job to do.