RH into RM frame conversion?

[Slakewell]

I know anything can be done , but how hard would it be to place a 75 RH motor into a 77 RM frame/roller? Are they both side port etc?

[80-85 husky]

72 ts cases were the same as rm125S cases... good chance, only changed the cases into RM 125 B

[LWC82PE]

RH is a 250. RA is a 125. I think we are talking 250's here?

[Oldfart]

What year frame are thinking of using ?? Rm  76-77

[80-85 husky]

right...

[Slakewell]

What year frame are thinking of using ?? Rm  76-77

I would use 77 frame with probably the 125 forks

[William Doe]

I gotta ask Mick why ? an RM 250B motor is i would have thought a better option in every way .

An RH motor into a pre 75 frame i get, a 74 KX 250 frame would be a good option or even a custom frame, Cheney copy or the like ?

I got  an RM 250B motor with no home  its apart but all there if your interested .

Bill

[LWC82PE]

I think if it makes use of spare parts you have then go ahead. May depend on intended use, do you want to even race it, or do you just want a fun and unique bike to build?

[Slakewell]

The few rides I have on a RH impressed me with the motor, I believed it was close to mid 80's power and out put.
Would others think the 77 RM motor is better?

[bazza]

When i rode DT's RN (earlier model) was impressed how much power it had down low.

[Oldfart]

you would be better sourcing a Rm 250 A (1976 ) package .... the A motor is very close in power delivery to a Rh 250.

The Rh frames were made of very thin wall chrome moly tubing ( imperial )  linked together with a super light one of  sand castings
in magnesium and Ali  and ended up with one hell of a light bike.
Very few of these parts carried on over to production models.

 

[gt96]

The few rides I have on a RH impressed me with the motor, I believed it was close to mid 80's power and out put.
Would others think the 77 RM motor is better?

I think you are spot on. First time I rode a 74 RH was 76 and I had an RM250A at the time. The RH engine was so much better that I wanted to swap it out at the time. The droopy TM slippery footpegs were rather distracting on the RH, but that engine was something else.
Recently, I have ridden fresh 74 and 75 RH's. The engines were pretty much identical and apart from the softer rear end on the 75, they handled very similar. Power and power type still leaves my RM250B for dead, and my B is not exactly slow.
Getting an up pipe built to match the original RH may be a little challenge.....
Good luck with the project and hope to see it out at some of the club events.

[Doc]

When i rode DT's RN (earlier model) was impressed how much power it had down low.

I concur, DT's RN had power to burn in a package weight of a TM125. A bike I could easilly live with