z400 sputtering problem..

[svtbolt04]

Well, It started as soon as I pulled the cap off to fill it back up with some gas. Maybe some water got in the gas through the vent hole, but I am not sure what else it could be. I took off the seat and looked at the air filter and it was fine. Infact, the bike ran perfect all day yesterday durring practice. I pull out the bike to go on a little ride, fill it up, then it starts to sputter in every gear about quarter throttle al the way up to WOT.

What should I do? Drain the gas? I dont know what to do. I also checked the CDI because it was over reving very easy in neutral.

Any help would be great.

[TRX450R_Racer]

Do you still have your parking brake? I'm not sure about your quad but I have seen some Yamahas that have a switch associated with either the clutch or parking brake that sticks. Check up by both the levers on the bars for a switch with a plunger that goes in and out. That might be your problem.

[Terry Arick]

There is a hole in the left side of your cylinder that drains the water from around the spark plug. If that is clogged then the Z will misfire because water is trapped around the spark plug. Take high pressure air to it if you have access, or take a small wire and run it  into the hole and see if water runs out. Clean your spark plug cap when done. Don't pull the plug until you clean out the drain or else the water will run into the combustion chamber.
Try it
,

[svtbolt04]

Thanks, I let it sit for about a half an hour and then Before I started it, I drained the bowl one more time. Started right up and I went in my backyard track and it was running flawless once again.

Thanks to both of you for answering.