2004 yz 250 intermittantly goes very rich

[marktrent]

I have a 2004 Yz 250 that goes rich to point of bogging or sometimes won't start. I go back 15 minutes later and it starts. When it starts bogging I turn the petcock off and as it runs the fuel out of the carb it cleans up and runs fine for awhile. Any ideas?

mark trent

 

[RM_guy]

Check your float height. It may be letting too much fuel in the bowl which would make it rich.

 

[Wilky]

Possible causes

1. Dirty air filter or to much oil in the air filter.
2. Stuck choke
3. Stuck float
4. Tranny fluid seeping past the main seal and getting into the crank case. If there is white smoke coming out of the pipe and it smells like burnt oil then the seal is probably the issue.

Fixes
The first three are pretty self explanatory. Cleaning the air filter and the carb should take care of these.
The fourth is a little bit more involved. If you have never replaced a main seal then get yourself a service manual if you haven't already or take it to the shop.

This, of course, is not a complete list of possible causes.

Scott

 

[marktrent]

Since it is so intermittant I'm thinking it has more to do with the solenoid on the carb or possibly with the choke mechanism. Transmission fluid is full. I didn't really notice any additional smoke. Float is definitely possible except nothing has come out the overflow tube. It feels just like the choke is on. What does the solenoid on the carb do exactly?

Mark Trent

 

[RM_guy]

Gas doesn't have to come out of the overflow for the float to be set to high. The fact that it runs good after running it out of gas leads me to the float height.

I should have asked, is this a new problem?

 

[marktrent]

Yes it is a new problem! I didn't think it was float height because it only does it every now and then.

Mark

 

[marktrent]

Well I found the problem. Broken reed valve. Who'd a thunk it would come and go like that?

Mark