2001 rm 250 broken piston, those in the know come give opinion please.

[Keith Kile]

well I bought this 01 rm 250 used like most people.. I could tell it been rode pretty hard. every since day one noticed a pretty good vibe in the pegs and a low rpm knock that went away with rpm.. the bike ran pretty good. I then pull bike down to the frame and replaced all bearings leaving motor on the bike. put PC platinum pipe and 304 silencer on it..along with rebuilding my forks and having pro action do my rear shock with 3 stage valving..new wheels, tire, etc. well I notice its alil rich as i have read most 01's are .. so with the jetting from PC I only take 1 jet# out the main and move the clip into the second spot in the needle. runs better feels good and starts on the first to second kick each time. well I run motul oil at 30:1 and just switched over to 110 leaded VP with same oil and same ratio. we unload today and tried to fire it up to notice it was alil hard to start. ( sat for 2 weeks) I thought nothing of it. went to track to play around some, was practicing my berms turns and looping around to work on this one turn.. I did this a couple times and the went to rest. 10 Min's or so pass and try to fire it up.. hard to start again with a slight bog right off the crank up when free reving. rev twice bog went away.. hit the berm a few more time and notice I have a rattle sound from what sounds to be the top of the motor.. I look for the first things.. like good on gas, kick start not hitting the pipe, plug is in good, pipe warm to touch but not hot. so I think maybe something like motor mount alil loose under the tank.. nothing bad make a few more laps and call it a day to check it out later.. well hit the same berm again to hear a clank and the bike shut off.. at this point I know I found what the noise was as when I went to kick it, it stop dead in its tracks.. long story short took home and tore top end down in the frame to find that I have a broken piston. the lower skirts on both sides are shattered. from what I can see so far is that my oil and fuel seem to be good as I have no scaring on the sides other than from the broken areas so I think its not lean.. next so scaring what so ever on the jug.. I will mic it at work tomorrow to see what it measure's out at... I guess my question is do you think that its a case of it was worn out when I got it and needed a piston and it was just loose in the bore and waiting to break? or something else?

when I first bought the bike I did look into the exhaust port while I had pipe off to look at the piston and it looked awesome no scratches at all. so its leading me to think that it was just over due for a fresh piston and rings..

I will add pics of the piston so I can have others opinion on this..

I will also be pulling the cases to check my bearings and also to get the piston debris out of lower case. and to check crank and trans.

thanks for your time and sorry to ramble on...

[quadracer87]

hang that piston on a wall!

get that beast going


buy a wiseco prolite

[stk563]

oh fuck take the cylinder in it needs a sleeve for sure. split the case take all the metal out and start over fuck dude that is bad how did it still run. when u separate case better take crank in and have them make sure its in specs because for it to destroy a piston like that something went wrong big time in ur motor. from looks of it the piston got caught on intake port and was jamming the top of the piston into the exhaust port meaning the wristpin was shot in that piston causing about 600 dollars worth of damage to ur bike.

[Keith Kile]

split the cases today after work and got all the metal out the bottem..rist pin bearing is flawless and so is the wrist pin clearance to the rod and the piston.. lower big end bearing seem good. none of them have any signs of trash running through them or heat.. did notice that the crank to case bearings are going to be changed.

the rod moves side to side and free play appears normal..rotates great, it has no up and down movement.

also the Cyl has no metal transfer or scratches.. still going to mic it at work when I get it cleaned up to see what the bore is.. to see if its with in spec.

does anyone know if the 01 Cyl can be honed to the next size? or is it plated?

looks as if I will be replacing the lower crank to case bearings and seals and a new piston and pin along with a new pin bearing to be safe, as soon as I determine the size piston its going to need and how the Cyl checks out.