TM400 in RM frame

[Marc.com]

Have spare TM400 engine and thinking about putting it in RM 250A frame, want to build RM400S, anyone done this conversion already

[JohnnyO]

Never heard of anyone doing that.. i think it'd be easier to buy an RM370

[cloggy]

 Super Hunky has a theory that the reason for the TM's extreme malovence lies in a variable advance. He postulates that as the engine changes temperature, so does the advance curve, hence it's extreme unpredictability. If that were so a better frame wouldn't help much.

[frostype400]

I reckon it would go well better suspension and frame might be able to handle the tm400 motor better tm400 in a modern bike frame would be fun.

[oldfart]

Marc, I dropped my TM 250 motor into a 250 B frame just to see what changes they had made.   Weight was the biggest factor along with width  mag to clutch cover.
I think  Tm 400 motor's are longer ??

[Marc.com]

Yeah I guess I was always a bit curious about the RM125S and why it exists in isolation and didn't have a 250/400 family. Already have RM370 and TM400 so thought I might build something in the middle.

Or else I will use the TM400 engine for some horror Frankenbike. Been buying them cheap and clean out of the USA at the moment so have surplus engine.

[frostype400]

You don't have a 71 72 tm400 pipe I can buy I just have to do the bottom end in my tm400 the cylinder is already done new piston awaiting some action.

[Marc.com]

You don't have a 71 72 tm400 pipe I can buy I just have to do the bottom end in my tm400 the cylinder is already done new piston awaiting some action.

Sorry mate, be nice to have another myself, I just bought one off the pipe division of the GMC corporation.

[frostype400]

Yeah I just wanted an original one becuase they look sweet no muffler has got to make a good sound as well.

I currently have a rm250a motor in a pe250b which is going back into an rm250a frame and will build a good pe250b as well best thing about suzuki I find is you can mix and match motors and frames as long as they are the same year.

[JohnnyO]

Have spare TM400 engine and thinking about putting it in RM 250A frame, want to build RM400S, anyone done this conversion already

I think you would be better off slipping an RM 370 motor into a RM 125S rolling frame,i have offered a motor up into one and it will fit fairly easily. As has already been said the TM 400 motor is a long unit and this limits its use in other frames .
I think the whole TM 400 death trap myth is just that, the original TM 400 apparantly had its dubious traits but the TM 400L and 400M were not a bad bike . Compared to the Euro stuff of the day they were a bit ordinary but in the right hands and with a bit of modern technology they are a reasonable vintage bike .

Keep us updated with your proposed project .

I can't figure out why you'd put a 370 motor into an RM125S chassis? You would end up with a bike not as good as a std RM370 and have to race it in the same pre '78 class..

[JohnnyO]

Yeah I guess I was always a bit curious about the RM125S and why it exists in isolation and didn't have a 250/400 family. Already have RM370 and TM400 so thought I might build something in the middle.

Or else I will use the TM400 engine for some horror Frankenbike. Been buying them cheap and clean out of the USA at the moment so have surplus engine.

Marc the RM125S is a '75 model and i guess you could say it's family are the RH250M & RN370M as they are very similar in design.

[Marc.com]

Matter of fact I slipped a TS185 into RM125S chassis years ago ( still have it) definitely 400 won't go into that space.