How to make a kx125 faster?

I have a 99 kx125 with a fmf gold series fatty pipe and a fmf shorty. I'm currently riding a 06 kx250f but I want to bring the 2 stroke from the dead and since I'm putting money in it and my b day coming up I'm gonna get some stuff so what would make it faster? I know they have the 144 bore kit but don't wanna do any engine work just to make it faster. ThAnks

Not much else you can do, make sure the jetting is right, I can't think of any ways. To make the engine faster without any engine mods, maybe some kind of airbox mods to make it breath easier

Suspension work will be the best bang for your buck. Then seat time.

A pro built motor from TDC would be the best thing you could do. Basic rule with any engine is, "No replacement for displacement" Except in the rule of a 144. Now TDC does do a 144 build that " I heard" is pretty friendly on jetting due to their port design.


144's can be very finicky to jetting and after many discussions on this subject, the end result is a 134 build. 144 are great if you are trying to gain every ounce of hp and willing to fine tune every race.


Otherwise, a 134 is a nice upgrade without the hassels.


It's no different in the minis. an 85, 100, 103 stroker and 105 or 7 builds are great. The 112's absolutely suck for jetting.


Get used to the reality that a 125/134/144 IS NOT going to pull like a 250F. Learn to ride a 2T like is supposed to be ridden and it will be faster than a F. A 4T is a lazy mans bike.

So, in that in mind, I will repost, probably, the greatest 125 vid ever recorded.

Spending all that money on bolt on stuff and not knowing how to properly set up the motor (squish & jetting), well you're just pissing in the wind.


I met jimma at the marshfield fair in MA this year, he was riding a 13 crf450 and man was he fast

Put a 250 motor in it..

As said, bolt ins won't get much. For the most part they'll mive power around, more peak at the expense of low rpm power, more lowend at the expense of overrev, etc.

Real power comes from real engine mods. Porting, head mods, big bore, etc.

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