Just idling...

Starts fine and idles...but as soon as I twist the throttle it dies. Sometimes it backfires and pops before it dies...

What could be causing this?

Take your carb apart take all your jets out go to a dirtbike store buy the exact ones. GO home clean the rest of your carb. Then drain your gas tank and put in fresh gas. Put it all together in reverse order and also check the fuel filter on the bottom of the tank.

Sounds like it's getting enough fuel to get it running, but starving when you hit the throttle. First pull the fuel line off the carb and make sure that you have good flow to the carb. If not, drain the tank and pull the petcock out of the tank. There's a filter inside the tank that might be clogged. If you have good fuel flow to the carb, you need to remove the float bowl and see if there's anything in the needle that's restricting the flow.Usually if that's the case, the needle doesn't seat and the carb just dumps gas and never stops eventually flooding the engine with fuel. Like mentioned above, check the jets and make sure they're not clogged. The pilot jet can cause the problem, but it usually comes with a very lean condition causing the header pipe to turn cherry red an a very short amount of time. The last thing is the accelerator pump. There's a diaphram in the accelerator pump that over time will break down and tear causing a major bog and a backfire when you wick the throttle. Also, if the bike is an 06, look up A/P mods. This is also something that can cause your problem.

I also forgot to mention that after changing the valve shim I washed the bike w/out the tank and w/out the air filter. I covered the air intake boot with a rag but may have gotten water into the air intake. Would this cause the bike to do this?

But I'll definitely look into all that was mentioned...thanks for all the info!

Generally speaking, water in the carb is not a good thing....:thumbsup:

But I say its a plugged pilot jet.

Can you give it gas with the choke on without it dying?

This couldn't have come at a better time. My bike was running okay, but needed the exhaust valve shims changed. Did that, put it together, starts and idles fine, but can't take any throttle opening. Tried spraying light mist of starting fluid while it was running and it immediately died, so I'm guessing I have too much fuel already. Also weird, when I shut it off, I can hear air escaping, like compressed air bleeding off. I don't see anything to suggest a leaking head gasket and it doesn't react to spraying carb cleaner around the outside. I'll pull the carb and check everything again.

It won't run with the choke on. Well if it's the carb I guess I'll have to check it for sure.

Yup it was a clogged main jet:/

Thanks for everyones help:)

What size was the main jet?

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