Carburator Issues

OK all you people much wiser then me. I have a question, my sons bike (2006 CRF 80 completely stock) runs great for about 40 minutes then it runs as if the choke is on. I can get us out of the woods by lifting the choke up about a quarter of the way and it runs great for a while then it will do it again. I'm going to take it apart tomorrow and soak it in carburator cleaner but any suggestion would be appreceated. Thank you for your help

Sounds like it may be a bit lean. As the motor gets warm it needs a bit more fuel and if it has none it will effectivly become leaner. When you turn on the choke it richens the mixture and the combustion area cools of just enough for it to run well then it starts to heat up. Go larger on the main jet.

If you put the choke on to fix it, the mixture is too lean.

It could be an air leak when it gets hot.

Possibly the electronics are getting over heated. CDI?

The simplest course is to first clean the carb and set the float height.

Check that the tank vent in the cap is open. You should be able to blow into the tank through it.

Thanks guys I'm on it and appreceate the help

As the motor gets warm it needs a bit more fuel

Whaaa?? No. The "choke" is an enrichening circuit which adds fuel for cold starts. A hot start is an air leak circuit. The opposite of what this guy says is true.

40 minutes is a long time. Tank vent was a good suggestion.

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