'98 Rm250 kickstart-little compression

[howsmydust]

Hi guys I've just bought a '98 rm250 from one of my friends last week and it has worked like a charm until tonight. I was riding across the corn field and as I went to enter the woods in 1st or 2nd gear it stalled. I then went to start it back up and the kickstart feels very soft (less compression) than normal. Its always had to be kicked over while the piston was in top compression to start up but now I cant even seem to find that. Does this sound like I broke the piston/rings or is there something else?? please help im skrewd as of now :|

 

[muddy226]

I've had that horrible feeling twice recently on my 2000 RM250. The first time some plating had come off the cylinder and damaged the rings and piston. I had the cylinder replated and new piston, flushed out crankcase etc., did the break in and started riding properly. At the end of a straight and approaching a jump it just died, and wouldn't even fire. It seems that the centre power valve had become worn and a little sloppy, and also when the replate was done the top of the exhaust port had'nt been dressed properly, the rings caught it and and broke, and the debris closed the spark plug gap. Another new piston and we're going again. Anyhow, if you've suddenly lost compression it could be rings, piston or plating damaged, and you should take the head and cylinder off before trying to start it again so you can find the problem before doing more damage. Good luck.

 

[howsmydust]

more options..

I was thinking around the same lines as you are saying but I talkd to my dad (not to expierenced) and he thinks maybe a reed valve stuck open possible carbon build up or something like that. It was running pretty rich fouled plugs quite often .. The compression is deffienitly not there like it used to be. What does spraying ether or wd40 in the carb kicking it over a few times and letting it sit a few hours to see if that cleans out the possible carbon sound??

 

[muddy226]

Well, sometimes rings get seized with carbon too, so I guess it wouldn't hurt too much to try it, but I don't hold out too much hope. Perhaps you should inspect the spark plug first and maybe shine a torch in the plug hole and see if there is any obvious debris, also you might try removing the exhaust pipe and shining a torch into the cylinder to at least see one side of the piston, and if you just gently push the kick start you should be able to get it in position to see the top of the piston also. While you have the exhaust pipe off give it a shake, and if it rattles try to recover whatever is in there and have look at that.

 

[howsmydust]

Alright well today is the day I get to try and fix it or tear it down and order what I need. Every one I've talked to thinks its the rings that went which is kinda weird cause I was only putting around the frontyard in 2nd gear and it stalled out, 10 mins later I tried to kick it back over and there was nothing.. I checked the plug last night it was fouled out so I cleaned it and checkd it still sparks.. Theres no way I can look down the plug whole but maybe I will try looking through where the exhaust would be if I can. I think this may be a long and disappointing day. :bang:

 

[howsmydust]

I've found out the problem by taking off the header and looking in with a flashlight.. a small sliver of the piston somehow broke off probabley causing me some big troubles now. the cylinder wall also has a small piece taken out either causeing the breakdown or caused by the break down. i hear this bike cant be bored out cause of the material used in the wall so i have to send it in to get replated?? looks like i may be fixing my toy then putting her away for the season.

 

[marcusgunby]

You can get the cylinder repaired and replated by someone like www.ericgorr.com

 

[sick 96 250]

you better tear apart your bottom end and make sure no pieces got down in there, that will cause a world of trouble and money. hope it works out for you in the best way

 

[howsmydust]

i have the whole top end taken apart right now sitting out in my garage. i talked to a local shop yesterday and the guy told me seeing it was a nikasil bore that i could not bore it out or put a sleeve in it. i dont think this guy knew what he was saying because theres ive found wcsleevescom and advancedsleevescom both have them for the 98 rm. its only a small piece of the cylinder (2 grains of rice) taken out just above the exhaust valve and about the same size taken off the piston. the head has no marks on it but the ex. valve is a little scuffed up but dosnt look like itd be a problem id have to repair.. i dont really want to take the whole motor apart to look for pieces but neither piece was accounted for hopefully they came out the silencer.

 

[muddy226]

Thats bad luck,but it could have been much worse. You need to know what caused the problem in the first place. Do you think the rings might have caught on the power valve ? If so, just draw filing the power valve should prevent reoccurence. Unfortunately for peace of mind you do need to dismantle the bottom end and make sure that no pieces are hung up in the bearings etc. As for repair, sleeving is an option but most people would opt for replating, which would involve chemical stripping of the original plating, welding the damage if necessary and then replating. To find out more about replating you could look at Forward Motion, Langcourt or Poeton Industries ( Apticote ).

 

[howsmydust]

Yeah Im going to go through the bottem end after i get the cylinder fixed back up.. i was going to put a sleeve in it cause i want to bore it out and get an oversized piston but i dont know if thatd be such a good idea. it has plenty of power the way it is but i wouldnt mind a little more to play with

 

[howsmydust]

as for what caused it im not to sure but i know the piston and rings havnt been changed in almost 2 years or so, the rings are not to to bad but will be changed maybe the piston finally gave out or clipped the valve or wall somehow

 

[howsmydust]

oh yeah i havnt gone through the bottem end on this before any tips or things i should watch out for?? i dont really wanna get into the gearing and such then have it come out not running when i put her back together