TTR230 Carb Problem (I think)

[jh2586]

EDIT: The bike MUST remain choked, otherwise it will die. We can let the choke stick in maybe halfway, but any further and the bike dies.

My buddy and I have been working on his Yamaha TTR230 and he's got the same consistent problem when trying to ride or even just blip the throttle. When we blip the throttle or give it throttle when riding (especially from a dead stop), it wants to die and the revvs lower as if the engine is going to die, then eventually, it will start going and it'll be fine after a certain RPM. We've tried messing with the choke and we took apart his entire carb assembly and replaced many of the parts (including float, jet screws, etc..). We talked to his father in law and he thinks that the engine might not be getting enough fuel quick enough because there seems to be a lag in when the bike gets power. We also took the tank out and the screen at the bottom of the tank didn't have much debris but we cleaned it out anyway. BTW, the choke must remain out otherwise the bike dies at idle no matter how warm the engine is.

Also, if we give it 'too much' throttle at once, it will die. Any ideas?

 

[augustiron]

Clogged pilot jet.

 

[jh2586]

Clogged pilot jet.

We replaced all the jets. Pretty much everything inside except for the float and needle. I'm thinking maybe it's just out of adjustment (position). I'm gonna try to back out the main and pilot jets and perhaps put one shim on the needle.

 

[augustiron]

Replaced with new? Did you check they were clear?
Only idling with choke is 100% classic indicator of a blocked pilot circuit.
Raising the needle and messing with the main is not fixing an idle problem.

 

[Maddevill]

Did you make SURE the passages the jets screw into were clear? Doesn't matter if you have a new jet when the passage is blocked. A bike that only runs on choke is a classic example of the pilot circuit being blocked.

 

[motomania2007]

ditto above.

Also old gas and contaminated gas will cause poor idling as will out of spec valves but that is unlikely and would focus on fuel and carb issues.

Did you remove and clean the idle air mixture screw circuit?

Is there any vacuum leaks?

 

[OaklandF4i]

Yes, shimming the needle can help help when applying a quick twist of the throttle...... but you cant address that issue until you address the idle circuit. Jetting circuits are cumulative, so if your idle/pilot circuit is off or not working, all the all the other circuits Needle and Main will also be off. So as others have already mentioned, you have to get it to idle correctly first. You may actually solve the other issues by just getting it to idle correctly.

Augustiron is spot on. Pull the carb and recheck the pilot circuit as well as the fuel screw (if it has an adjustable one). Ensure all passages are clear by spraying through them and visually looking into the carbs throat. Recheck your float height. Easy check for air leak is to spray a little carb cleaner around the intake boot seams with running engine. If rpms increase, you have a leak. But it almost 100% an obstruction in the idle circuit.

 

[jh2586]

Ok we got it working and idling good. It no longer has the stalling issue. The throttle responds very well. I turned the main jet at 2 1/2 turns and the pilot jet at 1 turn. Then the pilot air screw at 1 turn and then I adjusted the throttle position screw to elevate about 3mm. It runs like a champ! Took like 8 tries, (which was a pain in the ass to do) but in the end, it worked out. Seems like it wasn't getting enough fuel. Backing out the jets did the trick. :thumbup

 

[RickM]

Ok we got it working and idling good. It no longer has the stalling issue. The throttle responds very well. I turned the main jet at 2 1/2 turns and the pilot jet at 1 turn. Then the pilot air screw at 1 turn and then I adjusted the throttle position screw to elevate about 3mm. It runs like a champ! Took like 8 tries, (which was a pain in the ass to do) but in the end, it worked out. Seems like it wasn't getting enough fuel. Backing out the jets did the trick. :thumbup

Are there adjustable mixture screws for MJ and PJ separate from the regular pilot screw and Idle speed screw on the ttr? I have never seen something like that before

 

[motomania2007]

Ok we got it working and idling good. It no longer has the stalling issue. The throttle responds very well. I turned the main jet at 2 1/2 turns and the pilot jet at 1 turn. Then the pilot air screw at 1 turn and then I adjusted the throttle position screw to elevate about 3mm. It runs like a champ! Took like 8 tries, (which was a pain in the ass to do) but in the end, it worked out. Seems like it wasn't getting enough fuel. Backing out the jets did the trick. :thumbup

You have something confused.

The pilot jet and the main jet are screwed in tight (snug) inside the float bowl and are NOT adjustable.

The only external screw type carb adjustments are the idle air mixture screw and the idle speed screw.

I have TTR230 as well