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RM250 Top End Video - Need Advice

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I was told the top and bottom end on this 1996 RM250 were recently rebuilt back about 6 months ago and had minimal back yard driving.

The bike was not running good, fouling plugs, no powerbands and felt like the clutch was slipping, however we changed the plates and springs and still got the same slip like sensation, or lack of power....bike just didn't want to take off like it should.

See video and talk to me what you think?

http://s182.photobucket.com/albums/x274/kenthompsonhome/?action=view&current=VID-20111227-00025.mp4

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some detonation

that's all i can see in the vid..

side play on your crank is normal,

but you cant have up and down play

cant see the cylinder, so if it's good, just measure it, put in correct size piston and run that biatch

and search the reason from the detonation, what fuel are u using? high compression? moddified header?

correct ignition timing? correct spark plug?

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I was told the top and bottom end on this 1996 RM250 were recently rebuilt back about 6 months ago and had minimal back yard driving.

The bike was not running good, fouling plugs, no powerbands and felt like the clutch was slipping, however we changed the plates and springs and still got the same slip like sensation, or lack of power....bike just didn't want to take off like it should.

See video and talk to me what you think?

http://s182.photobucket.com/albums/x274/kenthompsonhome/?action=view&current=VID-20111227-00025.mp4

That doesn't look like "minimal back yard riding" to me. I would rebuild the top end, check the bottom and replace if needed, and re-jet. Does the head have those pit marks around the edge like the piston? May have had a ring break off and flop around a while.

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Thanks.

The sleeve was gouged up pretty bad. One of the rings was stuck pretty much flush with the outside of the piston in one area. The powervalve looked like it was a little worn from the piston...looks like it would touch it.

The new piston kit, sleeve and gasket kit are ordered.

Questions:

1. What would think my symptoms would be when this bike was running in this condition? Any noise? Lack of power?

2. How do you notice detonation on the piston? Hot spots or actual damage? Does it make any noticable sound in the motor while running?

3. If the crank and everything else is okay when I put in the new sleeve and piston, with a cleaned up PV.....I should notice an improvement, correct?

I will put a fresh batch of 93 octane and 32:1 mix before I do anything. Also, I believe the main jet is a 172 and pilot of 52 with 1467N (i think) needle in middle postition.

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Thanks Tailender. The top was pretty beat up.......but the rings were still in the piston, one of the rings was almost fused in one spot.

Regarding the head.....should I sand the pitted areas down smooth, or just get the high spots? Any input on what to do is appreciated.

Hope this thing has power after this small investment because a little Z50 would beat my RM right now.

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Why are you putting a sleeve in? I would get the cylinder re-plated. It would cost close to the same as a sleeve job but last a lot longer. It would run a lot better when the top end is new. For the head, I would make sure there are no metal pieces stuck in it and try to LIGHTLY grind the pits as smooth as you can or get another head. The pits will collect carbon and just cause more problems down the road. Be sure to check the crank. Maybe a bearing went and caused all the damage.

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Shop guy said I can go either way, but mentioned the sleeve option would allow me to rebore the next time around and go a little bigger on piston....only reason why.

I will probably spend a good hour smoothing that head out, if i cant find a reasonable new one.

This is my first top end issue ever....so i am learning as i go.

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All my bikes are yellow, but if I had your 91 kawi, I would have kept that! That thing looks nice! There are a lot of guys on here that have their cylinder re-plated, and as long as you keep the air filter clean and the jetting correct, plus regular maintenance, the cylinder will outlast a sleeve by a long shot. No need to overbore.

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