2004 rm125 motor Insights help needed

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8/8/2020 5:12 PM

I'm working on an on 04r rm125.

Does anyone know any upgrades I can make to the bike outside of the obvious ones? such as pipe/silencer/ reed block/p&p/bb?

I've heard I can use an 05 governor to improve response, what about 05-07 cdi?

What other tips/tricks?

Note this is a full build, I'm interested in making aFast engine not riding faster


"If you feel in control, you're not going fast enough" ~Mario Andretti

8/8/2020 5:45 PM

The 2005 and newer head, cylinder power valves and governor are better setup.

I wouldn't bother with reeds. Stock are good


8/9/2020 7:45 PM

I am in the process of doing one I will keep you updated. I did the 05 top end with power valve governor. I have had an 04 with just the 05 power valve governor before and that was a improvement alone. I have a 05 cdi I can try it on the 04 but I would imagine it won’t work because the 05 had a power jet. If you can find a factory cdi from 04 i here they are the way to go. I’m currently researching if having a aftermarket cdi programed will be an improvement as from what I have heard is the stock cdi works better than a vortex on the rm if you just use the maps the vortex come with. I tried a v force and stock with Boyesen carbon reeds were way better than the vforce. When I say way better I did not try it on a dyno but I did a test with the stock reeds then I tried the vforce and noticed little to no difference then I tried stock with carbon reeds and noticed much better throttle response and slightly stronger off the bottom. I’m currently trying the rad valve I will let you know how it goes. I’m told I should have the rad valve modified on the rm but I’m going to try it first. If you use a stock carb it will touch the shock spring with a rad valve or vforce. It doesn’t hurt anything but if your a perfectionist it may bother you.


8/9/2020 7:53 PM

You can do case matching and have your pipe modified to work with your motor mods as well.


8/10/2020 11:10 AM

This dude named Brody might be able to give you pointers on the RM build.....