YZ426F motor dies when jumping

I dont know if anyone else has had this problem but whenever I jump on my 02 426 the engine quits in mid air almost everytime. It runs and starts just fine. Has anyone else had this problem?

are you hitting the rear brake too hard in mid air without the clutch?..could be stalling it yourself. just something to ponder on the ponderosa. :thumbsup:


pull the drain plug on you carb bowl, maybee has a large lump of poo in it.

I am with BBW. Take the carb off and give it a good cleaning. Make sure to set the float level as well.

Great suggestions. Are there any instructions on how to clean the carb and set the float level? I didnt see it in the owners manual. :thumbsup:

Does anyone know if a product like Gumout would be safe to use to try to clean carburators on a 426?

Should be OK, just try not to get it on any of the rubber parts. Shoot the carb cleaner through every hole in the carb followed by compressed air.

are you jumping that high that your are leaving the earths atmosphere? Sorry...couldnt resist it :thumbsup:

I am curious to ask this

Do you have a problem with Stalling the Bike when cornering or in tight woods or ?

I ask mainly if the bike is stalling in mid air, two things come to mind. One has been covered and that is a cleaning the carb.

The other is idle speed, is you idle set high enough to keep the mass rotating in the gear you in. 1680 - 1720 RPM should be a range that would work. (I have a SenDec RPM Gage. My 2000 works best in this range)

A easy test would be to place the bike on a stand while running in neutral and then swing through the gears at idle, 1st 2nd 3rd, 4th 5th until the bike quits.

It should not stall in any of those gears... :thumbsup:

If it does and your idle speed is good, then start looking to see if the rear wheel is binding up, maybe bearings going bad, brake is dragging or the chain is to tight or binding

Make sure your spark plug cap is on tight!

Clean the carb and put an in-line filter between the carb and the tank.... Cheap insurance. Also check the carb drain lines for trash. A blockage in one of these lines can cause an out of balance situation in the carb that can cause the bike to die at idle when the throttle is released quickly.

Bonzai :thumbsup:

I helped a buddy of mine fix a problem like this that not even the dealer could fix.

Unlike your's wanting to die in the air ...this bike would almost always stall out when cornering.

It took him 3 months of taking his bike from shop to shop to finally do things right and bring it to the

"Man who knows everything"....LOL..ME!<---Don't believe a word :thumbsup:

I took the bike out to a track and sure enough I'd hit a tight corner and it would just die but once I let off the gas and pull in the clutch...the bike fired right back up...and ran perfectly...

The problem was where his kill switch wiring was routed beside his clutch cable. Every once in a while when the clutch was pulled in..the cable flexed and lightly smashed the wire (Bare) into a sharp seam on the radiator...thus causing the kill switch to be grounded out.

You may very well have something similiar going on...check your wiring!

I appreciate all the suggestions everyone gave me :devil:. All I have had time to do is drain the Carb with the bolt on the bottom but that did not work. I took it out today and it runs great "BUT" to test it out to see whats going on I would ride up to a small hill, pull in the clutch before going over and as soon as the back tire came off the ground.. boom .. dead engine. I have not tried all the suggestions yet. There are a few easy ones that I will try. The suggestions about cleaning the carb are intimidating and since this is my first 4 stroke I dont want to mess it up. I dont know where the idle adjustment is at yet and I thought about uping that to see if it helps. I will try a few suggestions but if it comes down to the carburator then I will need to take it to a dealer.

I will admit though. This bike is much easier to jump and control than my old two stroke, even with a dead engine in mid air :thumbsup:.

if it comes down to the carburator then I will need to take it to a dealer.

Dealers are good for buying new bikes and spare parts. Their service departments are generally best avoided.

if it comes down to the carburator then I will need to take it to a dealer.

Dealers are good for buying new bikes and spare parts. Their service departments are generally best avoided.


if you can jump a bike you can clean a carb. Get a Chiltons Manual or a OEM Yamaha Manual

There is someone on TT all the time that will walk you through or answer a question pretty much 24/7

Idle speed is increased by turning the big black plastic knob down on the carburetor. Clockwise for higher, counter for lower.

And the float level IS in the manual. Been there. :thumbsup:

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