TTR 125 rejetting not running right

Bought a 2008 ttr 125le just as a pitbike for the winter to hit some harescramles on and can't seem to get it to run right. I live in georgia and its about 50-60 degrees out right now. Currently has a big gun exhaust on it. The jetting that came in the bike was 100 and 17.5. It always started right up warm or cold and idled perfect and ran good except for at the very topend it sputtered and it didn't rev up very fast from idle, the colder it was the better it ran though. Took the airbox cover off one day to try to make it a little more powerful and it started running bad so i ordered a new 110 and 17.5 like everyone seems to run. Now with the new jets and airbox on it runs about like it did before except it struggles idling and goes from high to low till it dies, and it sputters and pops at high revs really bad almost like a revlimiter if you just hold it. With the airbox off it runs even worse and almost seems like the motor needs to be held wide open till it cleans out and runs right haha. but it never does it just revs slowly till it starts sputtering really bad. Wondering if anyone has any ideas? 


I have a 17.5 and 105mj, but I’m higher elevation then you. I would look at your needle. Maybe lean it out. Mine runs great.

I did a 20 pilot, one shim on the needle, 110 main, and cut the top of the air box out.  For you I would go up slowly on the main start at 105 or 107.5 and put the cover back on.  Get it running right, then start mods.  

So today I️ started messing with the fuel screw(with the air box cover removed still)it was at 2 turns out, moved it to 3 and that got the idle back to perfect, from there I️ fine tuned to try to find the best throttle response, before even from a dead idle it wouldn’t bog if you turned the throttle all the way, at the best point I️ could find it was still hesitant to rev, not as much pooping at the top end but definitely still there...thinking about moving the needle and trying again? Plug was white after riding for a while hard, this bike doesn’t get ridden slow much it’s mostly in the very top of the revs

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