I have a 85 LT250R with tired motor and the opportunity to buy 89 RM250 dirt bike with a strong motor for cheap. Will the RM250 bolt right in? If not are the mods difficult? The 85 has bad crank and damaged case and the RM250 is cheaper than the fix.

 

I don't believe it is a direct bolt in, but I doubt a large amount of mods are necessary. There is a guy on here by the name of 1986SuZuKiQuAdRaCeR, he has a '86 (same motor as '85) with an '89 RM250 motor in it. Maybe you can contact him and he could tell you exactly what to do. I would suggest using the RM's CDI box and associated electronics also....

 

It WILL NOT bolt in. You have to use all the RM electronics. I wouldn't even think about using the LT electronics.

You're going to have to cut the frame... UNLESS you toss your 85 frame and get an 87 frame. That would really not be that expensive seeing how 87 frames go for cheap on Ebay and you probably could sell your 85 frame on there easily...

Even if you do get the 87 frame you may require making motor mounts. That kind of stuff is really easy.

I used my 86's frame, it went in, but I had to make the frame rail where the engine bolts to like an 87+ frame, with room for a center exhaust port.

The 87 frame is stronger and offers better suspension than the 85-86 frame. It is also wider in the front an inch or two...

of course, talking about this work is a lot easier and less in-depth than actually doing it...

I STILL don't have the bloody thing running! I need a custom pipe to be made or the RM pipe to be professionally modified. I'm still waiting to get that done...

I won't even mention the possibility of vibration...

Good luck, whatever you do. I too have an 85 Quadracer case that sadly met with the chain... (that's not why I have the 89RM engine in there)

 

Oh, i just remembered you have to heat the frame up and bash it with the hammer to fit the case covers...

 

Thanks. I may give it a go, it doesn't sound too bad. Since the post I came across a Quadzilla roller and after reading some of the posts that maybe the better money-pit; if I can find a reasonibly priced 500 motor I may just unload the '85 LT250.