Stock jet's for a FMF exhaust?

Hey board, first post on here, the info has been great! I bought my son an '01 ttr-125 that has a fmf pipe on it. I read the thread on jet mod's and had a question. I looked and the jets in it now are 105/15. With the FMF pipe should I stick with the 110/17.5 combo or do I need to go bigger because of the pipe? FMF's site say's stock, which seems strange! :thumbsup: Thanks in advance!

Congrats on the TTR purchase! I am also a newbie here at TT but have already made some jetting/air box changes on my wife’s 2005 TTR-125LE with the FMF-Powercore 4 pipe. We first tried the 110/17.5 combo and noticed an increase in performance when combined with the airbox mod described in the “sticky” section of this TTR forum. The 110/17.5 really opened up the bike at higher speeds and made the bike run more like it should. Recently I tried the 112.5/17.5 combo and did not notice any improvement; in fact it could be worse as it seems to become flooded easier when stalling the engine.

Altitude is going to be another key variable into the size jets that you use, we live in Maryland and ride between 600’-1,800’ above sea level, if you live in higher altitudes your bike will run more rich and hence your best jetting may be stock or even lower. Try pulling the spark plug after a 20 minute ride to determine if your engine is getting the air/gas mixture it needs and go from there. There are some good write-ups on here about checking/reading the spark plug and the proper way to shut the motor down to get a good reading, etc… Good luck!

Thanks for the info! Gives me a good starting point, my elevation is also about 1000'. Picking up the jets today.

You can save yourself a couple extra minutes on the jet exchange if you leave the throttle cable still attached. Just remove the hose clams, gas line/overflow tubes, and the four screws in the bottom. You may need to adjust (turn in) the fuel screw in the bottom of the carb because of the larger pilot jet, ours runs good at about 1 1/2 to 2 turns out. Good luck!!

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