cylinders and info on rm125 early water cooled cylinders

[twinrock]

hey guys does anyone have any rm125 cylinders for sale 81-84 befor they went to full rear reed cage induction,
im lookin at putting a matching pair on a rg250, i measured up a rm84 cylinder at the wreckers and it looks like it will go on with out too much bother...
what i would also like to know which were the best? are they interchange able..different pistons? diff conrod? lengths that sota thing any help would be great thanks

[vmx42]

81, 83, 84, 85 all case reed cylinders.

82 full reed cylinder. Only year they used it. Different cylinder, cases and head.

There are variations in the waterjackets, and heads from the 81-83 aren't interchangeable to the best of my knowledge because of it. I haven't looked at the 84-85.

As for cranks, conrods and pistons I am sure somebody else can shed some light...

I would be shooting an email off to Stan Stephens in the UK. He does a lot of work on RGs and I am sure he could answer your questions far more accurately than I can.

Good luck...

[Lozza]

Question is WHY?  Only difference between the RG and RM is the RM has a bridged exhaust port but no AEC valve. RM has a 100mm rod length not sure but the RG could be 105mm. The RM cylinders didn't come in pairs either 
The only advantage would be using individual cylinder heads. If you want to do that the RG125 is a far better option.
Jeff you can always ring Stan for 4.95GBP/min,everything comes with concrete guarantee

[D project]

83 ran full reed also.81-84 all had the same pistons. 85 had a different head and flat top piston.84/85 had different rods.

[twinrock]

why u ask??
why do we do anything...
i had the 84rm cylinder in my hand right next to the rg cylinder and with out even measuring things i could see vast differences...both the exhaust and intake were much larger, also transfer ports were almost twice the size..!! all the ports in the cylinder were bigger and more of them...water jackets were much bigger too.. the figures on the rm125 claims 40hpr..!! the rg is 45hpr from a twin twice the capacity!! surely if u put 2 together one would expect around 60 or so hpr..and like i said they look pretty close match already the biggest prob i saw was that the rm cylinder was taller by about 5mm could just skim the bottom maybe??

[Lozza]

why u ask??
why do we do anything...
i had the 84rm cylinder in my hand right next to the rg cylinder and with out even measuring things i could see vast differences...both the exhaust and intake were much larger, also transfer ports were almost twice the size..!! all the ports in the cylinder were bigger and more of them...water jackets were much bigger too.. the figures on the rm125 claims 40hpr..!! the rg is 45hpr from a twin twice the capacity!! surely if u put 2 together one would expect around 60 or so hpr..and like i said they look pretty close match already the biggest prob i saw was that the rm cylinder was taller by about 5mm could just skim the bottom maybe??

Because 'big ports' dont always mean 'big power'. Show me the Dynojet dyno graph of a 40HP power reed 81 RM 125. Put a ignition on the RG and you will go to 50odd HP straight away, put properly designed pipes and your around 60HP, with a truckload more midrange.This is a 54mm 125 cylinder the ducts are barely enough to stick your finger in but guess the output of it? Anything look like it needs fixing?

 

[twinrock]

im going off factory quotes.. 1984rm125 40hpr ,rg250 45hpr, yes i know that factory specs are not dead acurrate but what one could assume to be accurate is the difference, ie even if the rm is closer to 35 that would still mean the rg is closer to 40...yes i could pump pump cash $$$ into ignition and pipes, how much would that be! whos gonna build pipes !? how long would it take..!!? and i would still have to rebuild my tired top end..and have it ported.. man it would be $2k plus later and possibly months of the bike off the road..
this is not an attempted to revolutionize the engine , i just thought if i was to rebuild it why not start with better cylinders i could match them on a spare bottom end on the bench when its fully sorted its a mornings job to swap it over..this would all come down to what price i could get the rm cylinders for..
as i have a rz engine with the yamagamma mounting kit ready to go...how ever..seems a shame to bench a perfectly good suzuki engine ,

so again does anyone have any cylinders for sale 85/84?