YFZ450 idle issue (VIDEO)

[bman120579]

Hey guys,
looking for a hand on my new toy. I started a thread on YFZcentral but maybe I can get an answer here:

My EXACT PROBLEM is when I start my YFZ it will idle till warm.If I throttle up it stays high and won't drop back. If I kill it and restart it after high idle it idles perfect again till I punch the throttle then it goes high rev again. I have a CHARIOT racing billet thumb throttle on the way. After I swap out the stock throttle how do I tame a hanging idle? I have enough slack in the line. My cable is new and smooth moving. When I push the throttle with the YFZ off I hear a metal on metal clatter from the open airbox. Might just be the slide moving but if has an extra noise that don't sound right. Stand by for a YOU TUBE vid link...

here is a link to the issue I am having. I can duplicate it EVERY time. It does not go away.

Please give me a hand with this simple yet annoying issue. Hate to tear it down as it does run so good...

 

[Braaaptor]

Have you had the throttle cable cover off the carb yet? It sounds like a mechanical problem with the throttle butterfly or cable inside the carb.

First thing you need to do is take the plastic cover off the side of the carb. Look inside and check out the cable. It may have become twisted, frayed, or loose where it hooks to the throttle shaft.

 

[karterphil]

I think your gonna have to take the carbie off and give it a good clean out and ensure that all slides are returning correctly, it could be an issue with the carbies pilot/idle circuit if it returns to normal after killing it and re-starting without actuating the throttle.

 

[Braaaptor]

I think your gonna have to take the carbie off and give it a good clean out and ensure that all slides are returning correctly, it could be an issue with the carbies pilot/idle circuit if it returns to normal after killing it and re-starting without actuating the throttle.

That was my other thought...Perhaps a sticking CV slide or damaged diaphragm is to blame.

This problem is going to require at least some teardown to figure out what's going on.

 

[1996BlasterBoy]

Yeah dude those 39mm Fcr carbs need to be real clean so I would pull it off and check everything out and make sure your cable is connected right because it sounds like the flat slide is smacking the top of the carb

 

[Wifesblaster]

Well it seems to me that it is not a mechanical problem with the cable or carb. If it was mechanical it would still be stuck when restarted. I have never owned a yfz and don't claim to be well versed in 4 stokes. Just my logical opinion.

 

[Wifesblaster]

I would say air leak or lean pilot.