Rm 125 Jetting help

[robertmoto10]

Hey guys I have an rm 125 and it will not sit in idle unless I give it a lot of throttle and when I brake ( with the clutch in) I still need to give it gas or else it will stall and I was told to re jet it but would it also work to move up the idle speed because with a little gas on it will stay runing I can not find the idle screw either

 

[2strokerfun]

What year bike?

 

[robertmoto10]

2005

 

[2strokerfun]

Start with removing the pilot jet and cleaning it really well. Should be able to look through the little hole and see daylight. You have to take your carb bowl off to access the pilot jet. This is usually the culprit and they get clogged.

 

[rmc_olderthandirt]

would it also work to move up the idle speed because with a little gas on it will stay runing I can not find the idle screw either

My first suggestion is to get a repair manual for your bike and get familiar with the basic adjustments.

As others have said, there is a good chance that the pilot jet has clogged. It is the smallest jet (has the smallest hole) and thus is the easiest to clog. But cleaning the jet won't help unless you also adjust the air mixture screw properly. I would start with the mixture, and if it can't be adjusted properly then tear into the carburetor.

The carburetor will have two adjustments that you can get to from the outside. One will be the idle SPEED and the other will be the idle AIR mixture.

The idle speed screw is generally a larger screw. It may even be remotely located, where the adjustment head is at the end of a cable so it can be placed where you can get to it. There may be a lock nut that keeps it from moving. The first step is to increase the idle speed until the bike will idle, even if that idle speed is ridiculously high.

The air screw is often "shrouded" and sometimes a little hard to spot. It can sometimes be a trick to get a screwdriver into it. This screw adjusts how much air gets mixed in with the fuel that the pilot jet provides. Turning the screw out (counter clockwise) will allow more air, leaning the mixture.

With the bike idling as slow as you can get it to keep running, adjust the air screw for best idle. This will probably increase the idle speed. Now re-adjust the idle speed to the lowest speed you can get it (or an acceptable idle speed) and then re-adjust the mixture. You may need to do this several times to walk the idle speed down.

If adjusting the air screw has little or no effect then it is a good indication that the pilot jet is clogged. Time to tear the carburetor apart and clean it.

If you can adjust the air screw, take note of how many turns out the air screw is. GENTLY turn the screw in until it bottoms, counting the turns as you go. Ideally, the screw will be between 1-1/2 and 2-1/2 turns out. If it is less than 1-1/2 it means that you are cutting the air down too far, which means it is running too lean, which means that either the pilot jet is partially clogged or it is too small. If the air screw was more than 2-1/2 turns it means that the pilot jet is too big.

Rod

 

[mathd]

This sound exactly the same as what my YZ125 did when the reed valve was good for replacment. It was also hard to start.