Off topic carb help

I know this may be off topic but, if anyone could help it would be great. My brother-in-law has a 1999 Suzuki RM 125 that needs a little help. The bike will not idle at all. You have to twist the throttle almost 1/4 to get it to idle. I was thinking maybe the needle jet needed to be moved to a higher slot. The throttle cable has some slack in it also and it is adjusted all the way out. I orded a new cable but do not belive that it is the problem. Otherwise the bike runs great. Are there any carb gurus that can help me. Sorry for the 2-smoke question but, I'm having no luck searching the web for answers. I have posted in other forums with no response.


Have you set the idle with the idle screw? Sometimes it is a screw sticking out of the carb or it can be that you twist the choke knob to adjust it. But 2 smokes really aren't supposed to idle. If you had jetting problems with the idle, it would be the pilot jet and air screw. Not the needle.

The idle screw is the choke knob and it has no effect on the bike at all. I set the air screw at 1 1/2 turns from bottom. Neither myself or my brother-in-law know much about carbs. Most of what I know has come from this group trying to learn about my yz400f. As far as trouble shooting we are both lost.

You said that you have to open the throttle 1/4 to idle. If you open the throttle all the way, can you hear the slide hitting the top of the carb?

Before you spend too much time, dismantle and clean the carb. If the slow speed circuits are dirty then you're not going to get it to run right and you'll just end up going in circles.

I've never noticed if the slide hits the top. I will listen today and see if it does. Looks like I'm going to take the carb apart and clean it.

Thanks for the help.

Sorry to say this, but it sounds to me like the crank seals are shot. Your first sign of this is failure to idle. My brother in laws RM never did idle. Not even when brand freakin new.

When revved does the idle hang for a bit then fall to nothing? If so, Id be lookin at the crank seals. Good luck.

When you rev it, it falls off fast and dies. Hope that is not the problem he just bought the bike. It was a good deal but, not if he has to split the cases. :)

My friend had a crankshaft seal blow. His bike just blew out a lot of blue smoke. He was able to just remove the clutch and replace the seal.

Consider installing new reeds.

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