Best yz 250 mods

my buddy put a Bills exhaust on his 14 and likes it not sure about jetting

I always used VP C12 fuel mixed with Yamalube 2R at 40:1. Was always clean when torn down for a top end. DEP makes a great pipe for it, Bill's is very good too.

There's a lot of great GYTR products for that bike, I'd start there.

Plan on mixing at least some race gas with pump. The YZ likes to detonate on pure pump gas. I ran C12 in mine. DEP Pipe, PC Long silencer. You can experiment with losing the reed spacer too. Dont bother with a RAD or VFOrce. They dont do anything for the YZ. Get an oversize front rotor and Honda master cylinder and you will be very happy. Oh yeah, go up a tooth on the rear. Spring it for your weight. These forks/shock are very, very good right out of the box.

Last...check the timing with a dial gauge. They are known to be off when new.

pipe, silencer and take the 178 main jet to a 180 and let er' eat

Do not run pump gas I blew my 12 up with 14hrs on it from new, I ran c12 50/50 with pump with kt at 40:1 never had a problem. If you like to ring it out a lot top ends don't last very long. I put a Fmf factory fatty and ti2 v force reeds and a 7oz fly wheel weight

I have always ran 32:1 Belrey H1r premix with BP 92 pump and I've never had a problem. Ran it for over 100hrs on a rm65 and the piston came out looking pretty clean.
If you have a stock head i would run 50/50 race/pump. I sometimes run it 36:1 and know people going 40:1 with no problems but anything over 40:1 and your top end will not last long.
Jetting is a HUGE factor on how all bikes run but its especially important on two strokes.

Like your yz250 my Cr250 was also prone to detonation and i wasn't wanting to run race gas simply because of the cost so i sent my head off to Eric Gorr/Forward motion and had them cut it for pump gas. Never had a detonation issue since.

Imo the very first thing i would put in my shopping cart would be a Magnetic drain plug, followed by V-force reeds+ pipe and silencer. All the major suspension companies are about the same. For KYB i would go with ENZO

As far as braking goes the best bang for your buck is a Tusk oversized front brake kit. Ive used their rotors and they hold up well.

I second both the hi-quality gas and the Bel-Ray H1R, except I've run mine at 40:1 with no issues. I seem to have the best luck with a richer main jet and the leaner needle that came with my '06. I think '08 and newer bike came stock with that needle though.

I put a Pro Circuit pipe on mine because It flattens out the power delivery a little bit and puts some on top. I understand the FMF Fatty is actually a better pipe if you like more power, though.

Put an oversize rotor and a braided brake line on that bike and she'll stop in a hurry.

Suspension-wise, just mess with settings and oil height. You'll probably be fine.

Do some research, best mod I've seen is re-adjusting the squish to around .040 to .045. Then it might be a little safe to run on pump gas with a strong and linear low to mid transition.

On my 2010 KTM 200 I put a thin base gasket, single ring piston, knifed the ports, advanced the timing a hair and adjusted the power valve. I don't know if advancing the timing and adjusting your power valve will help ya or not but my bike runs with 250 2 smokes on the moto tracks all day. Cheap ways to make it faster

My favorite mod on my 09 was 22mm offset clamps (shorter than stock).
I had stock, fmf and Scalvini exhausts at different points and none were clear above the others. I liked the scalvini best though if I had to pick.