TTR 125 Carb issues.

[Bobby-V]

Hey all. My brother asked me to help him with my nephew's TTR 125. It seems that it like all other TTR 125s had idle issues.

When starting the choke would need to be left on for a long time before it would stay running.

Even when warm the bike would stall out if choke was off.

These are common from what I've read about the machine.
This eve we took the carb off and blew some cleaner through it. I took the pilot jet out and it was completely plugged. I couldn't blow through it for anything. After some more carb cleaner and some work with a pin we managed to unplug the jet. I put it all together and the bike started up no problem. But this is where things get interesting.

The bike revved itself to unreal levels. I'd say round 3500 - 4000rpm. I turned the choke off to nil result. Revs stayed high. I looked at the slide and discovered that regardless of the idle screw position the slide remained at about 1/3 throttle. It was in such a position that the idle screw really offered no purpose.

It looked as though the previous owner used the throttle twist to adjust the revs on the machine in some strange bit of bubba-ing. I managed to adjust the throttle cable to a position where the idle screw actually did something. I figured this may just have done it but.......when i fired up the bike again it revved it's balls off, regardless of idle adjustment.

I may try to see if there's any more adjustment at the cable that can be done.

What I am wondering now that I'm recovering from carb cleaner to the eye (carb cleaner and contact lenses don't mix) is that maybe it has more to do with the choke valve thing than the throttle.

It seems I've created the exact opposite problem than that which is common on these bikes. Instead of dying out it idles at such high speed.......

Any advice out there would be awesome.


By the way - Every shop first aid kit should have a shot glass in it. They are perfect for eye flushing. Just fill the cup and put it up to the eye so the cup is completely around the eye. Lean back and let the water slowly flush out the eye. Repeat as required. It works because as soon as the shot glass is on the eye it keeps the eye open while flushing.

[Weldangrind]

Sorry to hear about the carb cleaner in the eye! I hope that's behind you.

It sounds like the slider might not be lined up properly. It's possible on every round slide carb I've worked on to put the slider in backwards, and that will prevent the carb from closing fully. The small ramp on the slider should line up with the idle screw.

[Bobby-V]

Yep, that's all lined up. If I remove the cable and re-insert the slider the same way it bottoms out completely with the idle screw out all the way. That's what led me to the throttle cable. I'm going to lube up the choke slider as well and see if perhaps that may be sticking as it seems it's prone to do. On the choke slider, it doesn't seem to have any marks that indicate any particular way to be lined up when re-installed.

How much of a gap should remain when the main slider is in the idle position?
If the idle screw is removed for sake of argument, should there be any gap between the slider and the inside of the carb or should the slider completely bottom out?

[katoranger]

I think the slide or the cable is sticking. It may be time for a new cable. Also make sure the twist grip moves freely.

[Bobby-V]

The throttle moves freely. The slider moves freely as well, it just won't bottom out even when the idle screw is adjusted all the way out. I think I'll start from the twist grip and work down to the carb itself. This thing is a pain in the arse.

[Bobby-V]

Finally got to it and my first hunch was the correct one!

The previous owner clearly lacked any mechanical knowledge because it became clear that he used the throttle cable to adjust idle. We pulled it apart tonight and reset it. Once everything was reconnected and re-adjusted we fired it up and it ran like it was new.

Now I'm looking for a new pilot jet and the suggested size is 17.5. I'm also thinking of going from a 105 to 107.5. 110 would be too much me thinks.

I am hooked on this working on bikes thing.....stop me I think I sold my soul for two wheels.

[Weldangrind]

Be careful; they're highly addictive.