92 RM 125 Problem...

[Stinger23]

My RM 125 was rebuilt top and bottom and has about 8 hours run time on it. Over the past ~4 hours of run time, it's went from running perfect to barely running at all...it was a gradual change.

First, it just had a slight sputter as the power band would come on or at the first crack of the throttle at high rpm. Then, it got to where you would have to occasionally blip the throttle to get it to get past the "dead spot". Then, it got to where it didn't run very strong at high rpms. Finally, it got to where it is now.

Now it won't run at anything over about 1/4 throttle under a load. If you just pin it from an idle in 1st gear, as soon as the power band hits, it will spit, sputter, backfire through the filter, etc. It absolutely does not accelerate. If you pin it wide open in neutral (normally a no-no) it will rev to probably 7-8k rpm and just hold there like that's as high as it will physically rev.

I've been through the carb 3 times and there is nothing wrong with it. I've checked the reeds and they look fine. I'm assuming it's either in the ignition or crank seals.

Hopefully one of you guys have had a similar problem and can help me out...I've been unable to ride for nearly 6 months because of this!!!

 

[Stinger23]

Nobody has any idea???

 

[rodsrm400]

I had a semiliar problem. Check the oil level in your transmission. Mine was sucking a quart every 3 hours of riding so I replaced the crank seal. It was pretty simple. I was told by a factory tech that our year suzukis were hard on the seals. It wasn't all that hard to replace the seal, just time consuming. I also checked and my jets were wront although the bike ran well at one point the jet was too small. So I changed it made my adjustments and it ran better. I then checked my reeds and flipped them even better of a ride. I went to 40:1 mix and it went nearly the best It could be. I now think I am starting to loose my top end as it has nearly 3 years on it and hasn't been rebuilt yet. BTW I have a 92 RM250. Im by far a suzuki tech, but I have been teaching Auto since 1999 and have been through hundreds of small eninges including 2 strokes. They are very touchy and any air leaks, extra fuel etc. they don't like to run well.

 

[RM_guy]

I'll bet your power valve isn't opening. There is a small set screw that holds the actuator to the shaft that can loosen up and let the shaft spin. You'll have to pull the cylinder to get to the access cover (just above the exhaust port) to see it. Or, the actuator rod became disconnected from either the shaft or the governor (inside the clutch case).

If you take off the side access cover (clutch side) and expose the actuator rod, turn the shaft with you fingers all the way and let go. You should hear the valves slamming back into place. If you don’t then the set screw is loose, letting the shaft spin.

The valves could also be sticking.

It could be a leaky crank seal too as Rodsrm400 said. Is your plug black?

Bad reeds would affect low end and make it hard to start. They wouldn’t affect top end as bad as what you’re seeing.

I wouldn’t expect jets either unless they are dirty. You said it ran great and then gradually deteriorated. Jetting won’t change over time.