Conversion of my RM250 with an YZ250 engine

The RM250 to YZ250 Conversion.

Hello all

I just finished the coversion but I still have to fiddle around with some details.

Ridingwise I have to see if it is any different from the original RM250 feeling. I found the RM a bit jittery at full throttle and the knifing in sand I found it first quite difficult to handle. I think it will make not much difference with the YZ250 engine.

Ripping the RM250 engine out.


Then mounts and axle thickness. The rear axle of the RM is slightly thinner so I took some time to find some can, beer or coke will do to fill in the missing half a mm.

I had to take of some material off the YZ250 engine mounts



Important were those little inlets


mounted and glued into the engine casing


Resetting the middle engine mounts by about 7mm


Taking off more material at the front engine mount and the front engine to frame mount points.


Engine mounted, the top mount points fit without any changes or dremel work


And here is the RmYZ250 :thumbsup:


Funny is that working on the engine became easier, I got more space on top, and more space for the carb too :confused:

Wow, that's a new one and pretty cool, congrats.

The knifing thing might be too little offset on the triple clamps or suspension setup.

You could try more offset, or lower the forks, or increase sag.

My only question, is that a Suamaha or a Yamasuki now?

Hi carver

Hmm I think I was spoiled by the YZ250 and when I got the RM250 I lowered the forks about 8mm. It helped, now I have overcome the knifing effect. The YZ engine is abit snappier and I think the flywheel is the reason. Comparing both they have a difference of 5mm between both in their setting.

Replacement parts was one of the most important reasons. Here our suzuki dealerships produce some 1000 bikes, all GN125 and why would they care if someone needs a piston or some roller bearings. Just peanuts.

The Yamaha guys are different. Luckily for me.

The OEM pipe of the YZ250 bolted in there, less touching points than the fatty, even the first rubbermount was the OEM YZ250 one. I had to enlarge the silencer about an inch though. Not what I would like on an exhaust. I remember sawing off some 4 inches when young on our bikes. :thumbsup:



Why do you have your brake line outside the fork? The correct routing is inside the the fork tube.

Hi there

I wouldn't know that is how I did get the bike. It is a 2008 RM250.



Why do you have your brake line outside the fork? The correct routing is inside the the fork tube.

He's correct. You'll want to reroute that brake cable to prevent snagging.

Cool project by the way :thumbsup:

Arne, very nice project!

very cool

Thanks a lot guys :thumbsup:

and a special thanks to all who made it possible, getting those parts needed to complete it.

It rides nicely already although I still have to do some stuff specially on the exhaust mounts. I wonder now how to call it, Sukiyama?



Cool project. I think Yamazuki fits well.

true it could be named that way, if you are die hard blue :thumbsup:

IMO a rolling frame gets me somewhere even if only downhill. An engine on the other end I have to drag around. So I believe you have to give credit where it is due :confused:



That's awesome! I want a steel fame bike just so i can weld and do engine swaps with it.

I think an aluminium frame can also be welded. But that apart I believe you have to make up your mind if you want it swappable for various engines like RM250 frame and Yamaha engine which can be converted back with the middle mounts (remove and reweld) all other stays the same. I think if the space between the RM250 set up and the YZ250 engine mounts would have been greater it could be done with a metal clip. Screwed on the older bridging to the newer mount.

As for the frame I am quite happy as it turned out. I think the engine lies about 5mm deeper in its mounts, amking all the other mounts fit, or a more or less fit. I used the elctric of Yamaha with one exception. The coil. Here I used the Suzi one.



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