RM - PE 400 Help please

[Roostin440]

Hi. I talked a friend into racing vmx with me. He bought a 1980 RM 400 on line. Well last night it was delivered and we discovered it is mostly a 1980-1981 PE. It does have a RM 400 motor. The vin says it is a pe frame. The rear wheel and swing arm are also pe items as well. We found a good RM frame near by that he will buy. What year swing arms will work and does it mater if they are from a 125,250,400? How do we tell if the forks are from a rm or from a pe?

Thank you,
Mike

[DR]

thought someone from PE Land would have answered this by now but since not I'll give it an uneducated shot

firstly Roostin, I'm preeeety certain that the RM250/400N/T swingarms are the same dimensions excepting a chain roller tab added or some other small difference. Shock mounts for the RM and PE are in different positions which you probably know. The 125 arm is no go due to the smaller pivot bearing size and being of a lighter build than the 250/400 require. Not sure about the difference in fork legs but check the triple clamps to see what they are as this may give an indication..for mine PE clamps would indicate it probably has PE forks also

[oldfart]

Ok I will chip in ......   Pe  forks are 36mm  250/400   1980 & 1981     swing arms are the same
                             Rm  forks are  38mm  250/400   1979 & 1980     swing arms are as what Doc has stated
                             Swing arms from a PE to Rm differ at pivot also  ...... width wise
                             Pe 250 and 400 frames are the same in years 1980 -1981      and the same can be said for Rm 1980  250/400

[LWC82PE]

Ok I will chip in ......   Pe  forks are 36mm  250/400   1980 & 1981 plus 82    swing arms are the same
                             Rm  forks are  38mm  250/400   1979 & 1980     swing arms are as what Doc has stated
                             Swing arms from a PE to Rm differ at pivot also  ...... width wise
                             Pe 250 and 400 frames are the same in years 1980 -1981 plus 82      and the same can be said for Rm 1980  250/400

if you want to save money i would stick with the PE frame, otherwise your gonna have to buy a RM swing arm and RM rear wheel which wont be too easy to find. The PE frame is dimensionally the same as the RM. youd just be saving a bit of weight from not having the rear frame loop and a couple brackets.

[Marc.com]

Yeah I would look about for a PE400 engine as well  , almost the same power, but much smoother and has primary kick starting. The RM400 engine was an old nail compared to the PE.

I would like Leith said stick with PE frame and swinger and throw your money into RM forks and good shocks. Shocks are the biggest improvement you can make to these bikes.

[Roostin440]

Thank you guys. We stripped the bike down to the frame last night. The motor runs great, so we are good to go there. Found a RM 250 frame for $99.00. He wants a rm swing arm and rear hub/brake. That may be a little harder to find. The forks measure 36mm. He may keep them, I'm not sure the 2mm is worth the cost. Good to know the 125 swing arm wont work. There are a lot of those for sale around here.

[flyingdg]

A friend is running 81-84 RM wheels on his 79 rm250, he told me it was a bolt up.

[LWC82PE]

wouldnt that make the bike illegal for EVO class though and make it a pre 85?

[flyingdg]

It's OK to run them here is the States. DG

[oldfart]

A lot depends on what you intend to use the bike for .....Enduros or  MX.