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1992 rm 250

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#1
i just got a 1992 rm 250 and it clattered bad so i pulled the the top end off and the piston has a bunch of pits in it and the top ring was seized and the cylinder head has pits in it to..the cylinder is scored but no deep scores just visible scratches...can the cylinder be honed? and it has a rod in it that says pro series has anybody ever heard of these are they any good? and the rod has side to side play but only a teeeeeeeeny bit of up and down play is it ok? oh and how do u know if the crank bearings are ok?
 
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#2
You may want to dissasemble the entire engine and inspect everything. If the piston and head is pitted, there may be peices in the lower end. If you don't remove those peices, your engine will eat itself.

The bottom end should have a little side to side movement but no up and down movement that you can feel. The rod is most likely a Pro-X or IMS. The main bearings should rotate smoothly without any noticable noise or roughness. They should be replaced when the crank is out.
 
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#3
well the crank rotates smoothly and i think the pitting was caused by detonation but i did find these little like metal ball things stuck into the piston? but there were only three of them......but there is a little bit of noise but i had my uncle look at it and he said they are fine..and he has had a lot of experience so i trust him:) but thanks for the advice:)
 
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#4
The little ball things are main bearings, PLEASE DO NOT RUN IT. Within an hour your bike will be toast again unless you get lucky and get 2 hours out of it. The bearings are wore out and are coming apart, my RM did the same thing I know what im talking about. And yes my crank rotated smoothly too.
 
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#5
oh man you have little balls stuck in your piston and you feel its ok because your uncle said so?wow, well when it makes a load knocking noise b4 it blows...just have your uncle pay to have it fixed...because i surely wouldnt want him to "fix" it for me....those "balls" are bearings...no two ways around that....and anyone that has just a little basic knowledge of any combustion engine would know that..:( do yourself a big favor...replace the top and bottom while its still not grenaded itself..
 
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#6
dude the little balls that im referring to are only a little bit bigger than a grain of sand they dont pt little ball bearings in a 250 and i dont have that much $ so i cant afford to take the bottom end all apart for nothing.
 
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#7
Like it or not, you have a problem and you need to repair it. Don't worry, you're not taking the bottom end apart for nothing. If you can detect any radial (up & down) play in your rod, you need to have the crank rebuilt. If you don't, it's going to Chernobyl and possibly take out a lot of other expensive stuff that you definitely can't afford. How long it will hold together without doing anything is hard to say. Eric Gorr has a buddy that's rebuilding cranks for $125:
"...my friend Ryan from Finishline Engines offers crank
rebuilds with parts for $125
His number is 1-920-382-2897"

The cylinders are all aluminum with a very hard plating for wear resistance. If the plating is worn thru anywhere then it has to be replated. If the plating is good and the cylinder dimensions and geometry are withing spec., then it can be honed. Do a search here on the subject and you'll get all the info you need. Don't rely on your uncle's knowledge unless he's familiar with plated cylinder technology - traditional techniques can't be used. If both the piston and the head show impact marks, there was something hard bouncing around inside there. I'd be inspecting everything to try to determine it's source.

If you don't have the cash to do this then you should wait until you do. Especially in the world of 2 strokes, Cheap is Expensive as is impatience. I recently bought a 2000 RM250 that some idiot cut corners on and both the bottom and top have to be replaced as a result.

Marc -
 
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#8
It's not the whole bearing you're seeing, its pieces that have been broken off. This is what happens over time of being revved to 10'000K.
 

IndyMX

Crash Test Dummy
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#11
billy madison said:
but only a teeeeeeeeny bit of up and down play is it ok? oh and how do u know if the crank bearings are ok?

If there isn't ANY up and down play...

If you have a teeeeeeeeny bit of up and down, you need to fix it.
 
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#12
billy madison said:
and i told u my uncle has had plenty of experience with bikes
I have plenty of experience with women doesn't mean that I understand them.
There is something definately wrong with the motor. If you don't fix it now it WILL COST YOU much more in the end. If you really believe what your uncle is telling you then WHY are you here asking us???? :whoa:
 

IndyMX

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#13
bruno670 said:
I have plenty of experience with women doesn't mean that I understand them.
There is something definately wrong with the motor. If you don't fix it now it WILL COST YOU much more in the end. If you really believe what your uncle is telling you then WHY are you here asking us???? :whoa:
Nothing wrong with a second opinion. What you do with it is your business. If you don't at least check out what many people have suggested, based on the information we have been given, is a serious problem, don't be surprised when it costs you a lot more to have the cases repaired cause you didn't take the time to check it out properly.
 
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#14
Also, take your flywheel off and see if you can move the flywheel at all. There's your rod bearings then there's your main bearings. Play in the flywheel is an indicator for main wheel bearings. But if you have play in this then they're really worn.
 
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#15
billy madison said:
and the rod has side to side play but only a teeeeeeeeny bit of up and down play is it ok?
billy madison said:
the rod doesent have any up and down play...
:coocoo:

WTF? If there's no play, why did you waste everyones time asking what to do about it? :bang: Keep in mind Billy that the collective experience found on this board exceeds that of your uncle many times over. Some of the folks here have been working on bikes for 30-40 years. They also bring to the table thier experience gained in occupations such as mechanics, engineers, and machinists. As Indy said "what you do with it is your business", but you would be foolish to ignore the advice offered here.