99 YZ400 backfire and no idle - Super Moto/Motards...

COWFIDDY · 01-09-2005, 11:28 AM

yz400 wont idle. i move the screw and nothing happens, and when its cold it will start faster if i use the hotstart insted of the choke. and when letting off the gas it back fires alot. i fixed an exhaust leak and cleaned the carb like 3 times. and it helped a little. the pipe is an e-series with disks and the last disk is solid with no hole, so the exhaust gets out through the disks. if i remove the solid disk it backfires worse. so im confused what my problem is. carb or exhaust. also can the problem be valve adjustment.

Catman · 02-28-2005, 05:11 PM

sounds like your carb is gummed up.Has it sat for a few months with gas in the bowls?? I have a 426f It did that shit all the time, now I always drain the carb if it's going to sit.This may not be your prob. just one I used to have.Yamaha makes a great carb cleaner you mix with fuel and draw it into the carb,let it sit overnight drain bowls and your done!!.....Good luck!

wiem · 03-02-2005, 07:58 AM

I think you must clean your carb again, but very very thoroughly,
preferable with a compressor (I don't know wether that word exists, because I'm from belgium, i mean a thing with air pressure, you used it to pump your tires...).

01-09-2005, 11:28 AM	#1
COWFIDDY Registered User Join Date: Dec 2004 Location: westpalm, FL Age: 26 Bike: 2-xr50 yz400 rs50 waveblaster Gender: Male Posts: 328	99 YZ400 backfire and no idle yz400 wont idle. i move the screw and nothing happens, and when its cold it will start faster if i use the hotstart insted of the choke. and when letting off the gas it back fires alot. i fixed an exhaust leak and cleaned the carb like 3 times. and it helped a little. the pipe is an e-series with disks and the last disk is solid with no hole, so the exhaust gets out through the disks. if i remove the solid disk it backfires worse. so im confused what my problem is. carb or exhaust. also can the problem be valve adjustment.

02-28-2005, 05:11 PM	#2
Catman Registered User Join Date: Nov 2004 Location: Da Nati Age: 41 Bike: 02-Gsxr1000, 00 gsxr750,cb750, gs750,99 955i, Gender: Male Posts: 1,782	Re: 99 YZ400 backfire and no idle sounds like your carb is gummed up.Has it sat for a few months with gas in the bowls?? I have a 426f It did that shit all the time, now I always drain the carb if it's going to sit.This may not be your prob. just one I used to have.Yamaha makes a great carb cleaner you mix with fuel and draw it into the carb,let it sit overnight drain bowls and your done!!.....Good luck!

03-02-2005, 07:58 AM	#3
wiem Registered User Join Date: Mar 2005 Location: zellik Age: 23 Bike: honda xr 600 supermoto Gender: Male Posts: 13	Re: 99 YZ400 backfire and no idle I think you must clean your carb again, but very very thoroughly, preferable with a compressor (I don't know wether that word exists, because I'm from belgium, i mean a thing with air pressure, you used it to pump your tires...).