Engine cutting out / missing at WOT.

[Honda_Matt]

Just started happening, my yfz is cutting out really bad at WOT, no other throttle position is affected.

I dont think it's a dirty carb, cuz it was cleaned pretty recently, although im not ruling that out.

I havent taken anything apart yet, so I dont know what it could be, hope it's not ignition.

Whats it sound like to you?

450 yosh full pipe & KN w/ jetted carb is about the only motor mods.

[Ride1Rob]

Not getting enough fuel at WOT will cause it to do this. Does it feel like it's falling on it's face, dying, about to shut off? If so, it's running lean at the WOT position. You need to adjust your needle one slot down. This will cause it to dump a bit more fuel at WOT. I wouldn't think trash/dirt in the carb would have it doing this at only WOT. But at the same time the question must be asked why did it start doing this all of a sudden with no modificatoins. Did you change jetting or anything?

[Honda_Matt]

Originally posted by Ride1Rob
Not getting enough fuel at WOT will cause it to do this. Does it feel like it's falling on it's face, dying, about to shut off? If so, it's running lean at the WOT position. You need to adjust your needle one slot down. This will cause it to dump a bit more fuel at WOT. I wouldn't think trash/dirt in the carb would have it doing this at only WOT. But at the same time the question must be asked why did it start doing this all of a sudden with no modificatoins. Did you change jetting or anything?
Nothing has been changed, jetting is correct and the needle position has been changed previously.

Its not like a miss coming onto WOT, but during WOT, every couple of seconds it falls on its face and picks right back up.

Also, I know what you are saying about the needle clip, but someone else might get the wrong idea, when you say adjust the needle down...

You mean, adjust the clip down, to raise the needle and give it more fuel.

[Ride1Rob]

Originally posted by Honda_Matt


You mean, adjust the clip down, to raise the needle and give it more fuel.


Yep! It seems that after you hit WOT it's starving for fuel. Either that or it's your rev limiter.

[Dr89]

weird that it just started happening after it had been running fine....

it COULD have somethin to do with the timing...but i would think that'd affect more than just wot...timing chain could be worn, etc :confused:

[Honda_Matt]

Originally posted by Ride1Rob
Either that or it's your rev limiter.

It does almost feel like the rev limiter, Ive got it geared so low I usually hit the limiter every gear it seems but Ive never, EVER noticed this at WOT.

Seems like its something new.

Anyway, im gonna tear it partially down 2moro, do a compression check, valve adjustment / check, clean the carb and check the timing out.

Ill let ya know if I find something wrong.

[Ride1Rob]

Originally posted by Honda_Matt
It does almost feel like the rev limiter, Ive got it geared so low I usually hit the limiter every gear it seems but Ive never, EVER noticed this at WOT.



Thinking it's more than likely your rev limiter...

[Honda_Matt]

Rev limiter taking a crap?

Do they go bad? Cause like I said, i havent ever noticed it til' now.

Rev limiter is in the CDI box right?

[Crazy lil punk]

CHECK YOUR AIR FILTER!! My yfz did the same thing, if I gave it full throttle it felt like I was bouncing off the rev limiter, when it really wasn't, but my air filter fell off and was just laying in my air box, but it back on, and it rips again.

[Honda_Matt]

Nah, it's not the air-filter.

It's clean, and secure.

check your wiring. i worked on a bike with the same problem. after checking everything i finally checked the wiring and found a short.

[Crazy lil punk]

Originally posted by Honda_Matt
Nah, it's not the air-filter.

It's clean, and secure.

Yeah, i figured mine might have been a weird case, but boy did it make it run like JUNK. Good luck on your problem man.