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09 yz125 best mods??


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I have extensive time invested in getting this bike faster.

If you wish to keep it a 125...considerable power gains can be had, but it gets a little more peaky (though not too bad). Race gas is a must for all out gains.

The GYTR 144 kit (which is an ATHENA 144 kit...nothing more) is so so. For retail of 850 bucks...it's truly NOT a good investment for 2 horses!

Approx 1/3 of that will will get your current 125 cylinder putting out more power.

If you want it to go bigger...and don't want a complete new cylinder... a 144 is fun, in an ideal world both bore and stroke work better...

I have a write up coming out soon on the 144 athena kit. I purchased one to develop - figuring a lot of people would get it.

If you want both your stock cylinder...AND the 144 cylinder, it's the best route to go budget wise...even after paying for modifications to it.

All said the 144 can put out 38ish hp relatively reliably - aka shy of something weird it lasts great. 40ish is not too hard either...but most users would like the 38 spread and delivery better...and almost all riders would go faster on the 38 style set up.

The 125 can stretch to 37-38, but its tough to ride!

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im pretty light 135 pounds, and the bike right now hauls ass with me on it. the boysens made a nice gain, just kept the powerband longer and got to it quicker but i would like to get the 144 kit but its not in the budget right yet. just looking for little things i can add on that will make it more ballzy, more getup and go.

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What type of riding are you doing?

I ride my 06 at 10,000 feet and I'm faster on it in the woods then my 06 YZ250 and 06 YZ450F.

I have an SST with a FMF Turbine SA, The 36 mm carb instead of the 38, Smart Performance suspension fluid, 2-3 extra teeth in the rear, bark busters and that's it. I do have an 18 inch rear but that's not essential. The bike works so good! I feel like I'm cheating and I never get tired compared to my bigger bikes.

On the track, your best mod is to practice starts and race tight tracks! You have the rest bolted on. If you go big bore, jetting can be tough. Ported, and you'll probably need race gas. I live in the sticks(Vail, CO) and race gas availability is limited(Denver).

Have fun!

KH

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if you wanna stay cheap, you could advance your timing a few degrees and run race gas, that will increase the hit for you. Most guys retard the timing, but hey, there not as fast as you apparently 😏

how do you advance the timing on a 2 stroke..?

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i started with the 144 this was a jetting nightmare ... after dialing in the jets on the 144 was not happy with the low mid still felt like a 125 so eric exchanged for me and sent the 165/60mm bore same porting low mid porting with slightly higher compression than stock... have to say i was very impressed and happy to rid myself of the 125cc powerband - had low end super mid and top overrev to the moon never in the year riding did i ever find the end to the end top pull..was also running cleaner with jetting good luck

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