I have a 2004 660 Raptor that I purchased new, it’s completely stock.

Since day one I have had a problem with sputtering/hesitation at the very low end of the throttle range just above idle even after it warms up. As soon as it gets some R’s it runs fine it only sputters at the low end. If I add some choke then it runs better so I assume it’s running lean at the low end.

Is there a low speed fuel/air mixture adjust on the carbs somewhere?

If so, what’s a good starting point on the adjustment?

Any help is appreciated.

Thanks

Brian

 

There is a low speed adjustment. It's located by the bowl gaskets. You have to pull the carbs to get to it. This does not need periodic adjustment. So, it probably not your problem. They should be 2.5 turns out if you are stock.

If you quad has been sitting a while, it could be deposits in the carb. It could also be a float adjustment. These seem to need adjustments periodically for some reason.

my $.02

 

agreed

 

DO check your air/fuel mixture screw settings! My 05 660 had a bad stumble at low throttle when it was new. I also rode another 05 (brand new) and it did the same. The screws were set too lean from the factory at 2 3/8 L and 2 1/8 R (they probably do this for emission reasons). I'd try setting them at 2 1/2 L and 2 3/4 R and see how it does.

 

Thanks for the great info guys.

I will check the float height and definitely check the pilot screws.

I have a service manual on CD but it doesn’t go into any detail about the pilot screws as far as adjusting or what they are for.


Ozark38,

I feel confident that this will help since you have seen this on 2 different new Raptor 660s.

Thanks again.

Brian

 

I have an 04 raptor that is stock through the motor also. It has exactly the same thing you are describing with yours, the motor doesn't want to rev when under about 10% throttle or less, then once its 1000-2000 rpm's above idle the thing wakes up and pulls hard.

Good information, i've been at the carbs cleaning them and checking the floats but didn't know what the smart thing to do was with the screws.

Thanks guys