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2 days old YFZ... Questions and Issues
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Posted by: Ryan

I recently purchased a YFZ on Tuesday. Definitly is a great machine... Its been about 3 years since I been on an atv again.

Im having a problem with the idle dropping when the motor gets hot. When I rev it up, the rpm's will drop to about 500 rpm above idle speed and stay there for a few seconds, then it will go back down to idle speed. Im wondering what this could be. I know when I hit the throttle to hard, it bogs. Im gonna try to go up a size on the pilot jet.... But could that also be the problem with the idle not dropping?

Also, i've yet to see the fan kick on. I check it all the time, and never see it running. And I feel the heat from the pipe right threw my pants. Im guessin thats normal.... but not sure.

Also, when im running threw the gears, sometimes I hear a rattling, and like knocking sound... Almost like something is loose and shaking around....

Note- this motor doesn't have more than 2 hours on it.... But I can't say I been taking it easy.

Any input is well apreciated

Thanks

Posted by: 06YFZ450SE

I say the idel is jetting and the bog is normal too get a bigger leak jet or a boyesen quickshot cover. That help my bog the header getting hot is normal and I bet it gets red too. that the jetting lean from the factory.

If you want it to run better jet it take the lid off and take pecook out the muffler.Do the free cam mod.

Posted by: jshtex

quote:
Originally posted by Ryan
I recently purchased a YFZ on Tuesday. Definitly is a great machine... Its been about 3 years since I been on an atv again.

Im having a problem with the idle dropping when the motor gets hot. When I rev it up, the rpm's will drop to about 500 rpm above idle speed and stay there for a few seconds, then it will go back down to idle speed. Im wondering what this could be. I know when I hit the throttle to hard, it bogs. Im gonna try to go up a size on the pilot jet.... But could that also be the problem with the idle not dropping?

Also, i've yet to see the fan kick on. I check it all the time, and never see it running. And I feel the heat from the pipe right threw my pants. Im guessin thats normal.... but not sure.

Also, when im running threw the gears, sometimes I hear a rattling, and like knocking sound... Almost like something is loose and shaking around....

Note- this motor doesn't have more than 2 hours on it.... But I can't say I been taking it easy.

Any input is well apreciated

Thanks

First off if it is that new I would try to get the dealer to check it out.

I don't think jetting would cause the idle problem you describing. But pretty much every stock YFZ can benefit from proper jetting. As for the bog when you stab the throttle, well all the quads with the FCR pretty much experience that. You can try to adjust it out but really after your used to it you won't really notice it that much.

The YFZ is kind of a noisey quad. Kind of sounds like it is vibrating apart. But it should be fine.

Yes you will get a warm leg from the pipe, especially if your running the stock jetting which is on the lean side. Don't pull off the air box lid and un-cork the pipe without going up on the main jet as you will just make it leaner. Lean is bad, a little rich is safer.

The fan on our yfz's will come on after a few minutes of running at idle. I don't recomend just letting it sit there running too long but it should come on.

As far as break in, I have tried it both ways, by the book and by running the ever loving crap out of it and truthfully I haven't seen a difference. Heck I have broke in a top end rebuild several times at an XC race. Bascially two plus hours at mostly WOT.

Good luck!

Posted by: jim_beam_racer

well the idling thing is normal it happens on mine to
the fan never kicks on ive only got it on once some people will hook it up to a toggle switch and turn it on while there sittin on the line or whatever
but you say its new you dont wanna run that motor to hard cause you still gotta break it in
run it good but dont beat the piss out of it or youll **** somthin up
and dont take the pee shooter out of the silencer yet either until your motor gets boke in

Posted by: Ryan

Thanks for the info guys.... Im definitly gonna go up on the pilot jet.

Does uncorking the pipe and taking the air box lid off really make a difference? And when I do take the pea shooter out (still gotta figure out exactly what that is) , is it gonna be louder? I'd like to keep this machine as quiet as possible.

Is there anything else that is corking up the motor? And what is the next size up pilot jet?

I still gotta figure out the problem with the idle.... You say its normal jim...... But it certainly can't be right. And its only when the motor gets hot, after about 10 minutes of riding it hard.

Any other idea's on what it could possibly be? I don't wanna have to bring it to the dealership. Im gonna have to pay someone to bring it there and pick it up..... I'd like to avoid doing that.

Thanks

Posted by: 06YFZ450SE

The peeshooter is the baffle and yes it makes the quad louder.The baffle and lid off and jetted right it does make a big differance. I think the next size up on the Piolt is a 45. I had the coke stick on mine it might seem its off but its not. Play with the coke like out and in a couple times and see how that works out for you.

Posted by: ktmbill

Ryan try this 50 pilot needle in the third clip from bottom main jet 172 fuel screw 2 turns out. No air box cover open exhaust. If the YFZ is a 06 or newer you will have to order a needle for a 05 YFZ.

Posted by: scrimmy

you need the ncvq needle. i sell them. pm me if you want one.

Posted by: Ryan

quote:
Originally posted by scrimmy
you need the ncvq needle. i sell them. pm me if you want one.

What the hell is a NCVQ needle... And this will solve which problem?

KTM, I will probably try that.

How much louder will the quad be if I take the baffle out? I wanna keep the noise to a minium, don't want the quad to be more than 5-10 decibals louder...

Thanks

Posted by: ktmbill

It will be louder but not to bad. Try it if it's to loud go to a 48 pilot 1 clip higher on the needle 170 or 168 main

Posted by: #17YFZRACER

ive got the core out of my stock exhaust and it isnt to loud. really has more punch and sounds 100% better.

Posted by: JForestZ34

On my YFZ it used to idle high like that if I would pull in the clutch or or let off the throttle.. What I did was turn down my idle. I know they say it idles at 1600rpm or something like that. I turned mine down to maybe around 1000 and it made a big difference.. It doesn't do that anymore.. As for the bog mine does it too.. I was going to uncork my pipe and then get it jetted.. As long as the shop will do it..

James

Posted by: #17YFZRACER

you can do all that yourself. took me about an hour and a half to pull the pea shooter and re-jet, put a new needle in and a fuel screw.