Other Yamaha TTR 125 (4T) carb help

2smoke

2smoke

My niece has a TTR 125 that her grandpa purchased for her and set the idle on it. His intentions are good but he really doesnt know what he is doing. So I took her and my boys out for a ride this morning and I noticed that her bike is idling unusually high. So Im poking around and found out the she still had the choke on. But even still her idle is really high. So I bust out the tool kit find my find my fine tip screw driver and start poking around. I'll be damned if there isnt an Idle adjustment on her carb. There is however on the left hand side of the carb what appears to be a fuel screw that controls the air fuel mixture. On the right hand side there appears to me some other type of adjustment screw but I cannot get a good bite on it with the screw driver. So what Im thinking is that the carb needs to be rejetted for our elevation and the air fuel screw needs to be set correctly. My reasoning for this is that the more I turn the air fuel screw in (clockwise) the higher the idle goes untill you basically shut the fuel off. The more turn the screw out (counter clockwise) the lower it gets untill it dies or floods out.

Anyway Im looking for some insight on getting this carb adjusted correctly.
 
bobkyle2

bobkyle2

I think that is the same carb that is on my KLX... There is an idle screw.. Its on the left side of the carb.

Also check the throttle cable adjustment.. Theres an adjustment on the bars

More than likely it will need to be rejetted and clip moved... They come from the factory really lean... Pilot screw is on the bottom of the carb faceing down
 
SRAD97750

SRAD97750

Moderator
Staff member
OK, i want to throw 2 cents in...

The idle adjustment on my KTM carb is the choke lever, but instead of pulling it up, you "twist" to adjust idle speed. :prof:

The mixture screw should be around 1-1/2 turns from all the way in. Bring the idle up a little with the idle adjustment, then turn the mixture screw (leaning) slowly until the revs peak. Then back it off 1/8th(richening) of a turn and reset your idle speed to the correct idle.

Shoot us some pictures. -BIG DAN
 
2smoke

2smoke

SRAD97750:
OK, i want to throw 2 cents in...

The idle adjustment on my KTM carb is the choke lever, but instead of pulling it up, you "twist" to adjust idle speed. :prof:

The mixture screw should be around 1-1/2 turns from all the way in. Bring the idle up a little with the idle adjustment, then turn the mixture screw (leaning) slowly until the revs peak. Then back it off 1/8th(richening) of a turn and reset your idle speed to the correct idle.

Shoot us some pictures. -BIG DAN
Click to expand...

Im liking your input Dan. There is only just one adjust screw on the carb and Im pretty sure that it is only just the mixture screw. When I messed with it, the further in you tightend it the higher the revs got untill you ran the screw all the way in, and the engine would die. So I backed it out about 1 1/2 turns or so started the bike again and slowly started backing the adjustment screw out till the idle came back down. But then when you would snap open the throttle it would (hesitate) bog and the revs would come up. Which tells me its to rich. So at my next opertunity Im going mess with choke. But its on a cable mounted to the handle bars, so Im unsure if that is adjustable. As Kyle mentioned I did mess with the throttle cable length but it really didnt do much.

As for pictures. Its my niece's bike, so its stored at her dads house, but they do only live just down the street. So............. Im going to play with the bike first with the new info that I have. If I cannot get the idle adjusted it correctly I will be sure to bust out the camera and take some photo's of everything that I was able to find and mess with.
 
bobkyle2

bobkyle2

Image

Thats almost identical to the ol KLX carb...Pilot screw's on bottom... Sometime there is a brass covor on it.
 
2smoke

2smoke

Thanks for the link Kyle:thumb:. So the screw I was messing with is the "idle screw" So the pilot screw is the one I really need to be messing with then I suppose. I would have never thought to look under the carb for that. I dont even know if I can get to the bottom of it with screw driver. I'll just have to look at it again.
 
bobkyle2

bobkyle2

Rejetting is a must... Those bikes are lean from the factory...The TTR's have a moveable clip also...(I had to use a TTR needle in my klx.. To get a movable clip)

If you cant find the piolot screw on bottom... Look for a little brass covor... Sometime you have to drill them out.. Or find a way to pop that covor off (Or so i have read online)
 
2smoke

2smoke

Cool Thanks again. I dont remember how much they paid for the bike. But I want my niece to have a good riding experience, and having an engine that operates correctly with good throttle response, will help her. Thats what I love about this place. Somebody always knows an answer to the question you have in reguards to motorcycles.
 
bobkyle2

bobkyle2

Also... If you de-baffle it.. Or put a pipe on it....And take the snorkle out of the top of the Air box... It will help a TON.... Exspecially after a rejet :banana:
 
2smoke

2smoke

bobkyle2:
Also... If you de-baffle it.. Or put a pipe on it....And take the snorkle out of the top of the Air box... It will help a TON.... Exspecially after a rejet :banana:
Click to expand...

Yeah well Im not gonna spend much if any money on it. I'll let her daddy (my brother) do that. But since he is away at a school in So Cal for the Navy. I figure its the least I can do. Maybe even pull the aircleaner out and clean it. Dont even know if thats been done since they got it.
 
Top