TTR-90 ideal jet settings?

3 replies to this topic
  • Crew Chief

Posted February 18, 2010 - 05:47 PM


I used this site to find the best jetting for my wife's TTR-125 and it runs great now!

But the boy's TTR-90 is jetted stock, which is just awful. I've cleaned the carb a few times and put a new plug in it, but it still won't run right, even when re-assembled per the manual. It runs OK on the choke (idles too high), but won't idle off the choke and dies when you snap the throttle from idle. It will run well at the mid- and upper revs, but he spends most of his time at putt-putt speeds in 2nd gear, so I need it to run well down low.

Is there a preferred jetting set up for the 90 for use at or around 1000' ASL?

  • Crew Chief

Posted February 27, 2010 - 10:56 AM


Really? Nobody can help?

I'm at the end of my rope, here. I've rebuilt this carb 4 times since October, the last time (last night) I stripped it down to nothing and put it in a warm detergent parts washer to try and get it clean. It's not a dirt issue, the tank, petcock, fuel line & carb are sano.

Is there another solution? I think the float level is OK. What else is there? Should I move the clip on the throttle needle?

It just won't idle off the choke, and won't carburate at all (choke or not) at anything from idle thru mid-range. The top end works fine.

While the choke's on, if I snap the throttle off idle at any engine temperature, the engine dies. It doesn't bog and die, it simply goes silent, won't catch idle again and then stalls. Conversely, when I slooowly apply throttle while idling on the choke, it again goes silent and stalls. There's just no getting the carb to work, no matter how you work it.

When I start, the pilot air is 1 3/4 out (per the shop manual), the clip is in the middle position of three (per the shop manual), and the idle screw is about 2 1/2 out (which is just my WAG). I move the two screws in 1/4 turn increments to find a good setting, but so far it isn't having any lasting effect. The weather today is clear and mid-40s with low humidity.

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  • usmcvet

Posted February 27, 2010 - 07:24 PM


I'm having carb trouble with my son's 90 too. But, as far as jetting goes, everything I've read says with a stock pipe to use a 90 main and a 15 pilot jet. Good luck.

  • alleycatdad

Posted February 27, 2010 - 08:02 PM


I know you've cleaned it upteen times, but you're describing perfectly the symptoms of a plugged pilot jet. It's truly tiny on the 90, but acareful cleaning of the pilot jet solved this exact problem perfectly for us!



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