I wouldn't be posting this without searching the whole forum, but my search function doesn't really work. My '04 raptor 660 runs great for the most part, bought it used, maybe 25 hours on it. All maintenance done when it should be. But for some reason when I'm just cruising along at low throttle it feels like the engine is slowly stalling down, like loading up with fuel, and if I keep the throttle at that position it will almost bog out then it will open up like mad for a second then settle back in. It does this in any gear as long as it is at the part open throttle position. Only mods I know of are that the spark arrestor was pulled out of the factory muffler and lost, and the carbs have been jetted to make up for this. Plug is burning an even tan on the insulator, a little black on the electrode. looks to me like a close to perfect A/F ratio. Any idea why the loading up feeling? Is this just a carbureted thing that all of them do? Any help would be greatly appreciated!

 

Air filter maybe?

 

I am not sure exactly what is wrong. Not a normal thing. Check air flow first. You are lacking something.... maybe sufficient back pressure. These machines have such high compression. I would go with an aftermarket pipe. good luck

 

The lack of back-pressure thing sounds like a possibility. It is running stock exhaust but the entire spark arrestor assembly from inside the factory can has been removed, just as if it would be removed for cleaning, but it was never re-installed. The carbs are jetted to keep the AFR right, but lack of backpressure would lead to more pronounced problems at low rather than high RPMs, right? Someone help, I may be on the right track but this is still just an educated guess.

 

I think no spark arrestor is your issue,and i don't think that your jetting it is making up for it.

 

I agree with above. Might as well get a better pipe. Also check all vacuum hoses. These machines run so tight that one small thing not right will result in noticeable power loss.

 

Sounds like good advice to me! Thanks a lot for all the help! I was considering a new pipe but plan to listen to a few on YouTube before I decide. I like the thought of the SuperQuietRace pipe, not sure who makes it at this moment though. I don't need a lot of noise, but I do want performance. Also, I know most pipes specify jet size, but what if I go with a pipe as well as an aftermarket airbox? And while I'm upgrading, what does everyone think of the Edelbrock carb for the 660 Raptor? Anyone run one?Anyone know anything about jetting one? Once again, thanks for the help, I think i know where I can get a stock spark arrestor for the time being until I can get an aftermarket pipe.