Whenever I punch the throttle in first or second gears it cuts out on me, why does it do this, i have a K&N Power Kit and FMF Power Core IV on it. Any help would be great.


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~~Mike

'99 400EX, FMFpower core IV, WB Triple rate shox, AC Nerfs, K&N Power kit, Renthal Bars, etc...

 

Did you do any carb rejetting? It sounds like you are running lean. You need to go with a larger main jet at least and you might need to change your pilot also. If you don't have any idea what to do you may want to contact a reputable dealer and have him jet it for you.
Scott.

 

My 95 300ex does the same thing.. it is all stock. Would this still ahve to do with the jetting, i wouldn't think so, But what else could it be?? any help ???

Exer

 

I personally don't think it is lean. I think it has something to do with the accelerator pump flooding the carb. I have learned to deal with it by keeping the revs up. Especially on hill climbs.
phil

 

Mike,

Does it actually die or just bog before accelerating? If it is bogging, you more than likely need to re-jet - check the idle mixture screw first.

When I run my 400EX at low, low speeds, especially in second gear, it will die suddenly when I give it gas. This only happens when the engine is lugging slowly and I am barely moving. I agree with Phil, that this is probably due to an issue with the accelerator pump. Either it is doling out too much fuel or too little. I've never had this problem when racing or seriously riding, only when I'm screwing around or slowly crawling through crap trying to clear a new trail.

Regards,

Dennis

 

Mike, if in fact it is a jetting problem, the pilot jet controls the mixture from idle to approx. 1/3 throttle, which sounds like the area you're having the problem in. One quick thing to check if you've altered the filter system would be to make sure the carb boots are secure to the airbox and the manifold. The slightest leak there would give you a lean condition. With the improved breathing you've given your engine you need to be two sizes fatter on the main. If that isn't what you have, it could be the solution. At any rate it would prevent burned valves & other expensive repairs. One other thing, too, when you say you "punch the throttle", if your're at full throttle in 1st or 2nd, then all the foregoing info on pilot jets is not pertinent cuz your by-passing the other two jets & going straight to the main, so get yourself two sizes fatter on the main, check your carb boots & I bet your problem will be gone just like your ride will be g-o-n-e (as in quick!)
Cal, the Az hardpacker

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[This message has been edited by hot_shoe_cv (edited 08-20-1999).]

 

Condensation (water) in the bottom of the carburetor float bowl produces this symptom--when you open the throttle, the main jet sucks up the water, instead of fuel.

With no cost and a little effort you can at least eliminate this possibility--drain the carburetor from the dump tube (better, remove the float bowl), drain the tank from the reserve petcock position, and fill with fresh, clean, dry gasoline. Add some fuel conditioner as a precaution, if you want to. Then try it! Good luck.

Tree Farmer

 

Mike,

I would recommend trying to adjust your idle mixture screw. It is a real a$$ breaker to get to - up behind the idle speed screw - but you can get to it with a real small screwdriver and a little effort. Try backing it out in 1/4 turn increments (more rich) and see if it doesn't fix your bogging. I'm guessing you're running a bit lean on the bottom end.

Regards,

Dennis

 

It just boggs down, i rejetted when i got the pipe

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~~Mike

'99 400EX, FMFpower core IV, WB Triple rate shox, AC Nerfs, K&N Power kit, Renthal Bars, etc...

 

Fuel filter??
If you got a bad batch of gas, maybe theirs crud in there.