Jun 3, 2001
i just purchased a new 2003 KX250 and after break in the bike seem to run real low on power up top. the air crew at the moment is 2 turns out and im runing 32:1 premium unleaded with silkolene pro sx.
also it is very hesitant before going into band. should i lean it off a bit?


Nov 24, 2001
I have an '03 KX250 also and it is not a top-end screamer. Short of porting I doubt you will be able to get a whole lot more on top. I added an FMF Factory Fatty pipe and PV spacer and a VForce reed cage to mine and it works alot better than stock. The hesitation off idle is gone, the midrange is stronger, and it adds a little on top too.

As far as jetting, currently I'm running one size leaner on the pilot and main. But I'm running race gas at 1,500ft(~450m) elev. and ~70%humidity, so these settings may not work for you.

Leaning your bike out a bit could help with the hesitation off idle, also, switching to race gas or 50/50 race/pump may help make the bike SLIGHTY "snappier". The VForce helps out on the low-end as does the PV spacer, and the pipe adds a little everywhere. If you prefer more top-end, I've talked to several people who really like the Pro Circuit pipe for more power on top, but some say that they lost a little low-end.

Hope this helps a little.


Aug 15, 2002
The best thing to do for the top end on your KX is SHIFT! Not trying to be a smart ass, but the KX is a different baest than a CR for example. With precise shifting the advantages to lower RPM power can be felt, especially accelerating across the chop on a corner exit or in the whoops. The advantage being that the wheel doesn't break loose and start kicking all over the place like a top end screamer, it just keeps grabbing ground and throwing you foreward. People ask me somethine what kind of muffler I'm running on my KX, because it seams so quiet. It's stock, yet I still clear all the jumps and am up front in the first turn (for at least a lap or two..) Use what you have, shift early and see the light!
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