YZ 400 Flooding out????

6 replies to this topic
  • kevin1209

Posted August 19, 2006 - 05:35 AM


I just bought this 98 YZ400 about a month ago. It ran really good, and there were no problems. Now it has been in my shed for two straight weeks, with temperatures outside getting to 105 degrees (I live north of Dallas, TX). I pulled it out last night to start it up. It kicked over just fine, but every time I touched the throttle, it bogged down really bad. I could never get the throttle to rev the engine at all, it only killed the motor like it was flooding it out.
I need some advice on what to do to investigate the problem. Did the extreme heat in my shed screw up something? :thumbsup: It haas easily reached 120 degrees inside the shed. Or is there something else I need to look at? I need to fix this so I can get ready for fall riding. :ride:

  • quailboy

Posted August 19, 2006 - 09:49 AM


check your carb adjustments. also are you geting warm? choke stuck out? hotstart stuck out?

  • kevin1209

Posted August 19, 2006 - 10:06 AM


I haven't adjusted anything since the last time I started it, so I don't understand why it is screwed up now. It has only been a few weeks, and it was hot outside the last time I started it and rode it around.
The hot start is fine, and the choke is working. I used the choke yesterday to start the bike, and once it warmed up, I released it. The bike idles just fine. It justs floods out when I grab the throttle, no matter if I twist it a little or a lot. It's like the throttle is dumping pure gas in with no air at all, but otherwise the idle mix is fine. :thumbsup: :ride:

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  • theclone

Posted August 19, 2006 - 11:55 AM


sometimes mine does the same thing unless you let it warm completely up. I'm talking like 10 minutes.
what about a clean airfilter? sometimes its the simple things.
and can you rev it with the choke on?

  • kevin1209

Posted August 20, 2006 - 11:36 AM


I won't rev even with the choke on. It has me baffled because it starts on the first or second kick, warms up with the choke on, and will sit and idle great with the choke off after it's warmed up. But giving it any throttle kills it.

  • quailboy

Posted August 20, 2006 - 12:32 PM


try the airfilter. i doubt that you lost a jet so the gas is just dumping in. so you must not be getting enough air to burn the gas hence the flooding. or something in your carb could be plugged so you can try and clean it or run it as much as you can and see if gets better. your gas could be crap. not sure what else could be wrong

  • kevin1209

Posted August 20, 2006 - 01:43 PM


I'm thinking maybe the extreme heat dried out my air filter. I'm going to try to clean it again and oil it. Hopefully that fixes the problem. Any other suggestions?

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