I have a stock 2004 YFZ 450. My buddies ride quads too one has a 2003 pred heavily modded, one has a stock 1986 250r(amazing bike), but my real competition is a 2004 Honda 450r, thats also modded, where should I begin with mods to be able to smoke these guys on a pretty low budget for now$300-$700...please comment...later fellas

 

HMf pipe and a k&n air filter will boost you up alot!! oh and dont for get jetts!! or go out and get all of those and a hot cam you will notice a big difference with all those things and you should beat them!!

 

Sounds like a good plan to me.

 

rejet, take the air box lid off and the baffle and u'll be close to piped performance, but it will only cost u 3 bucks instead of 300

 

Cam mod, lose the lid, K&N filter, new slip on, rejet and you should be all set. Total investment=a touch over $300.00 if you do the work yourself.

 

mabe u should pump out the gas from their quads and pour in gatorade instead wen their not lookin and then race them and im sure ull win. haha

 

That's the ticket!

 

Taking off the air box lid and rejetting gets you 2 pony right off the bat, if you want more put in a pro-flow K&N airfilter kit. Also stick a Hot cam in there. You might want to change sprocket size which can really effect your speed. Heres the gearing break down.

Small front sprocket, Large back sprocket = More Acceleration: Recomend 13 teeth front, and 41 teeth back
Large front sprocket, Small back sprocket = More Top Speed: Recomend 15 teeth front, 40 teeth back

Keep in mind these ratios are great for the LT-Z400, but they might not be as good for a YFZ, mabey some one else might know.

P.S. Stick a good CDI box on, you can gain a lot of RPM's from doing so.