Please Help!

Ok A little background on my problem. I own a stock 06' YZ450f, I haven't adjusted anything on it, until now. I was trail riding with a buddy and following him and we came to a steep bank he jumped and landed fine so I followed, but when i came off the jump all i saw was a giant pit of mud. I landed in it and it killed the bike. The mud was about waist deep. The bike sucked mud and water in on top of the piston. Thankfully Nothing made it to the bottom end of the motor. So I tear the bike down clean the cylinder, head, and carburetor, put new rings in and put it back together. I can't get it to start at all with out twisting the throttle repeatedly and it won't idle. I take the carb off and clean it again getting more mud out of the jets. Well it still won't start unless you give it about 1/8 throttle and still no idle. I take it to my local shop and let them adjust and fool with it. They said everything looked fine with the valves and timing so they cleaned the carb yet again. When they blow through it with an air hose they get even more sand out. well they get it starting and idling. The carb still has the stock jetting and setting now all except the pilot air screw, but now here's my problem. The bike is running lean, the spark plug electrode is solid white, and it is popping out the exhaust way more than normal. Also the idle hangs for a moment after you apply the throttle. I've tried adjusting my pilot air screw but it doesn't seem to help it much, and about the point that it does seem to make a little differenence the air screw falls out, and I have been unable to find any air leaks. My local shop is stumped and I'm beggining to wonder if my bike will ever run right again. What do I need to do?

I had a similar problem with my 03 WR and all I can suggest is checking/ cleaning the passages related to the diaphrams on the side of the carb.I think there are a couple of screws for the cover.I would also check your throttle slider height inside the carb measured from the motor side.For a Wr its about 3-5 mm, a #3 allen wrench helps with this.I really hopes this helps as i messed with mine several times before getting it normal again.

make sure your valves are in spec. If the intakes are getting sucked up that can be where you get your hang idle from. Make sure you float height is good.

another thing you can do to make sure 100% there is no air leaks is to start the bike up and spray carb clean around the intake where the air box goes to the carb and where the carb goes to the engine. Just spray away and listen for any difference in engine noise.

Also pull your fuel screw out and make sure there is the washer..spring and o-ring. Make sure the o ring is 100% good. maybe even get a new one on there. If it is bad then you can have air suck threw there and can cause a lean condision. Do a idle drop and see how many turns out you are on the fuel screw. you should be no more then 4 turns out max. if you are out that far you are going to have to go up on the pilot.


Sounds like the hot start may not be closing all the way.

I had the same problems with my 06' 450. Running lean, popping on deceleration, hard to start, high rpm's at idle at times. The shop could not find anything wrong. So I went to the jetting forum and found the solution.

Changed jetting to 48 pilot and 170 main. Put a fuel screw in, tweaked the fuel screw, no more problems. Starts first or second kick even when engine is hot. Very little popping and still very fast. So check out the jetting forum and I am sure you will find the proper jetting for your area.


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