2004 RM 125 Help Please


I am working on my cousins 2004 RM 125. The bike has no bottom end at all. When you going to take off it just boggs. But once you fight to get the rpm's up it works really good.

This is what I done so far.

Compression test 140PSI

Adjust carb float. 

main jet 380

pilot jet 37.5

Checked reeds look good. 

Clean out pipe (stock)

repacked muffler (stock)

cleaned and oiled air filter

replaced left side crank seal.

There is no adjustment on the exhaust valve but I did check to make sure it moved freely. It quite a bit to push up the lever compared to my 2000 RM 250.

So if you guys have any idea on other stuff to check or what to do I would appreciate it.


It is a little low on compression and you never mentioned where the clip is at on the needle "much more important than the pilot". I'm assuming the 2004 has the round slide carb where the jetting runs different than the newer models. And what's the gearing on the bike?

Thanks for the reply. So as far as the needle clip goes I tried all runs the same. The gearing does not matter the bike ran fine with the gearing it has.

Thanks again.

New top end and clean the power valve sounds as if it might not be closing all the way.

I think I may have found the problem. I decided to check the reeds again with a flash light. There are gaps everywhere. Then I done the water test and the water just poured through. So I hope this is the problem.

reeds will make a huge difference in jetting, take you for a ride if you will.
that or what is his powervalve adjusted at?

As far as I can tell on this year of 125 the power valve is not adjustable. I done some research on it and it seems like it is fine. So I really hope its the reeds.

So I installed some new V-Force 3 reeds. The bike is work way better still need some fine tuning play with the jetting a bit but I think I got it. It pulling pretty hard through the gears and pulling wheelies pretty easy. So 140 psi is not bad compression  for a 2004 RM 125. 

If I run into any more issues I will post.

Thanks everyone for the help and input  :ride:

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