YFZ450 Jetting .

[mxpimp2000]

An alternate way to figuring out if you're too lean or rich is to examine the spark plug. After a few seconds of full throttle running, quickly pull in the clutch and stop the engine (Do not allow the engine to idle or coast to a stop). Remove the spark plug and look at its color. It should be a light tan color. If it's white, the air/fuel mixture is too lean and a bigger main jet will have to be installed. If it's black or dark brown, the air/fuel mixture is too rich and a smaller main jet will have to be installed. While changing jets, change them one size at a time, test run after each change, and look at the plug color after each run.

After the main jet has been set, run the bike at half throttle. Any pinging means too lean. Blurbbing means too rich. Excessive smoking is also an indication of running too rich. As before, you can check the plug color. If it's white, lower the clip on the jet needle to richen the air/fuel mixture. If it's dark brown or black, raise the clip to lean the air/fuel mixture. Next go along slowly in one of the lower gears at less than 1/8 throttle and move the throttle quickly to 1/2 throttle. If the engine does not pull strongly. Sort of gasps for breath and only runs well after the RPMs build up, it is an indication that the needle is too lean.

[Gommer450r]

okay thanks ill try that out tomorrow thanks alot hopefuly this helps

I have a 06 yfz450 with DG Xcellerator exhaust. Any i deas where to start. im in Indiana. Also no airbox lid. Thanks.

[stevestauff]

does anybody here have a florida setting ?ihave a whitebrothers slip on thats it any recs oh and lid off.

[quad4114]

48 pilot 178 main 4th clip down on needle prodesign air filter with no lid and r & d bowl on carb 100 octain fuel

[yfzrider690]

I just had mine dynoed at craze deals in winchester bay two weeks ago. I have a mmad port job, mmad warpspeend intake cam, cam mod, 12.5:1 piston, yoshi rs-7 full exhaust, modquad adapter with k&n. I am running a 170 main, 45 pilot, 3rd clip on the ncvq needle and 2 turns on the a/f screw.

[stevestauff]

well what did it dyno at.

[yfzrider690]

It dyoned at 48hp and 32 tq. It was done at craze deals in winchester bay, he said a stock yfz does 33 on his dyno and his dyno reads around 3hp low.

[stevestauff]

they showed a yfz dyno at that with cam mod. exhaust and the lid off without porting and stuff.

[yfzrider690]

Originally posted by stevestauff
they showed a yfz dyno at that with cam mod. exhaust and the lid off without porting and stuff.

Who showed that? A dyno is just a tuning device and everyone reads different. So just cause one shows 48 doesn't mean he would get that on another dyno. I bet on the same dyno he would be around 40. Everyone gets so caught up by what there quad puts out. I can tell you I was in Florence a couple weeks ago and no other 450 with just exhaust and filter could even come close. So what does that tell you???