Old RM guys

MaxPower
Profile picture for user MaxPower
Posts
2696
Joined
8/15/2006
Location
NJ US
MaxPower
Edited Date/Time 3/13/2014 12:13pm
Help me settle a meaningless debate please. The 77 and 78 RM125 were very close to being the same bike but for a few parts. Did they share the same exact cylinder? I say yes. Right down to porting specs. My Bud sayssays no. The 78 was tamed a touch in port timing. I'm right, right?
I wish we had a 100 Challenge and big turnout for it like you fortunate guys in So Cal. That sounds like a blast. It's probably good we don't have one. Because my life would be consumed building a bad ass 100 to race
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minifig-phil 3/7/2014 8:48am
3/7/2014 8:48am
A is 1976 and is a 56mm bore
M is 1975
B is 1977 54mm bore
C 1978 also 54mm bore
Sanchez
Profile picture for user Sanchez
Posts
156
Joined
4/1/2008
Location
Potomac, MD US
Sanchez 3/13/2014 12:13pm
3/13/2014 12:13pm Edited Date/Time 3/13/2014 12:15pm
The 78(C) model came with "keystone" type rings for better sealing. That was the only difference between the 77(B-model) top end. Cylinders on the 77-78 model are interchangeable, and yes the porting specs are the same too.

Also, the PE175 top-end will bolt right on for that model year as well. Just need to replace the rod with the PE model and you have yourself an RM175 super vintage cheater

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