YZ 400F Engine HELP

Hi guys,my 400 motor was completed today, has std Wiseco piston kit, head rebuilt by Eric Gorr, 2003 yz450 Cam mod , ngk CR8E plug and using 2000 WR Exhaust. Started after couple kicks for first time with choke out. I allowed it to warm up and pushed choke in and it stalled. Restarted easily and i played with throttle a bit allowing it to run a bit over idle rpm, then after about 5 mins i noticed the head pipe was starting to glow so i turned motor off right away. Any ideas what this could be ?

Just did a search , say its NORMAL to glow on idle with choke out ..

Still have the problem with it not idiling when i push the choke in . Any help ?

Try turning up the idle speed knob. Then get back to us.

I did that also, turned the knob fully clockwise and no rise in idle. Unless i have the direction wrong?

its normal its due to no air flow. Dont worry, yzf250 does it sometimes all the way to mid pipe.

Unless i have the direction wrong?

No, that is the right way.

I would make sure the idle adjustment is working, it is a simple threaded mechanism that acts as a stop on the throttle pulley.

More likely is your pilot jet (also called slow jet) is clogged. Try clearing it w/ a shot of WD-40 or something.

Try that and get back to us.

Hope this helps.

Your carb is varnished up... Tear it down and make sure all the jets and passages are clear. :)

i'll have carb cleaned 2day .Will post results after. May be the problem as motor was down while for rebuild.

Carb was fully stripped down and all parts cleaned etc...But still very low idle.. Could it be WR pipe with YZ Jetting ?

The idle screw on the carb does the same thing that twisting the throttle does, it opens the slide. If the idle is not increasing as you turn the idle knob clockwise, then either the knob is backed out so far that it is not making contact with the throttle slide yet, or the cable connection between the knob and the pin that threads into the carb is broken. Start the bike and crank in the idle knob until engine speed increases. You're not changing mixture or carb settings, you're just setting how far the slide will stay open when you let go of the throttle grip.

Hi guys,my 400 motor was completed today, has std Wiseco piston kit, head rebuilt by Eric Gorr, 2003 yz450 Cam mod , ngk CR8E plug and using 2000 WR Exhaust. Started after couple kicks for first time with choke out. I allowed it to warm up and pushed choke in and it stalled. Restarted easily and i played with throttle a bit allowing it to run a bit over idle rpm, then after about 5 mins i noticed the head pipe was starting to glow so i turned motor off right away. Any ideas what this could be ?

Dont worry about it , thin metal glows when hot ! Quit F-ing around and go ride that thing ...jeez ! A bone stock new bike will do the exact same thing .

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