Brand new 07 yfz

[kevinxbx123]

i have a brand new 07 yfz that was a leftover. i want to put an aftermarket exhaust on it like fmf powercore 4. will i have to do any thing with the jetting? the bike has less than an hour on it. thanks

[Honda_Matt]

Yes, unless you want to blow it up, it will definatley need to be re-jetted.

Let us know what kind of pipe you have, or will be getting for sure and what part of the country your in, for altitude purposes and someone will give you a good ball park range of where you should be on your jetting sizes.

[#17YFZRACER]

i would wait till you break it in but you can do what you want. and yes if you put a pipe and filter on it you deffinately will need to re-jet.

[kevinxbx123]

what exactly does it do when you re-jet it? i am new to 4strokes i used to own a banshee

[Honda_Matt]

Jetting 2 and 4 stroke engines are the same.

Rejetting the carb, is removing the existing jets that fuel is delivered from the float bowl, into the carburator and replacing them with a larger jet, to deliver more fuel.

Running a pipe & airfilter on a motor allows it to breathe alot better, get more air in and out.

Now if you leave the stock jets in there, that are tuned for a somewhat restrictive exhaust and airfilter(stock), and replace the atv with aftermarket exhaust and airfilter, it will have a lean condition.

More air, same amount of fuel.

Running lean will increase engine temps, and more... Ends up doing damage and you'll need a rebuild.

Putting larger jets in compensates for the better flowing engine, and gives it a proper air/fuel mixture & better performance.

Just like the banshee, (2stroke)
If your running lean, youll have a whiteish spark plug, if your running rich, it will have a black spark plug.

Running rich won't hurt the engine other than performance decrease from too much fuel.

[kevinxbx123]

alright man i understand, thanks for the help. im gunna just wait untill its fully broken in. thanks bro

[leveldrummer]

for what its worth, re-jetting the stock bike will show you alot of gains, if you havent noticed, alot of the stock yfz's have a "bog" when you stab the throttle, it hesitates for a second before it revs, proper jets will usually fix that problem. the stock bikes come jetted like crap, most people think its for emissions purposes, so if your going to put off getting a pipe and such, i would still jet it anyway. you will be glad you did.