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400ex engine problems...please help

1788 Views 3 Replies 3 Participants Last post by  mud99
I will try to keep this as short as possible....the quad will fire right up and idle and purr like a kitten with no knocking, smoking, or ticking for about a minute or so, and you can even give it throttle and it will respond great, but after a minute or so it will begin to start cutting out and then die within a few seconds. Once this happens i cannot get it started. If I let the engine cool off and try again the next day it will do the same thing. I have adjusted the valves a couple weeks ago because of this same problem. After I adjusted them I went on a hard 3 hour ride at the track, then parked it for 2 weeks, now this. I have readjusted to valves, they were not out of spec by much, but this time, it didn't solve the problem. It's almost like it cranks and runs great, but when it gets hot, it will die. I haven't checked the spark plug, it is hard to get to, I will check it next. It really doesn't seem like it is timing or carb issue because it does crank right up and run great for a minute or so. Right before it dies it will smoke just a little, but other than that, nothing. Thanks so much for reading, please let me know if you have any suggestions, I'm thinking maybe my valve seals are leaking, but I'd love some other opinions.
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It sounds like the float in your carb is stuck open. When they do this, they will start and run until they over load with gas and then they will start cutting out and die. It sounds like it's flooding and that would explain the smoke.

Try just barely turning your fuel cut off valve on where you just have a tiny stream of gas running to your carb and see if it runs any better. This isn't a fix, but it will help you determine if that's the problem or not.
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