I just installed one of those "Pure Polaris" performance mufflers on my 2004 SP700. It's actually made by White Brothers and has a series of disks at the back. You add disks to increase airflow and sound, and remove them to decrease both. Mine came with five disks and White Brothers recommended starting with that.

After installation things are a bit louder and a LOT more powerful, especially in the low end. I'm pretty happy with that. However, on my carbed 700 I'm noticing a slight hesitation. When the machine is idling (thumb off the throttle) and then I stomp on the throttle, the engine hesitates for a moment before revving up. If I hold the throttle open just a bit instead of letting it sit at idle, the hesitation vanishes and I get instant takeoff. (This thing would probably wheelie now if I wasn't worried about flipping an 800 pound machine.)

This makes me think the carb jetting may need adjustment to compensate for the increased airflow (technically, decreased resistance to exhaust airflow). I've never adjusted carb jets before so 1) I'm not sure I'm even diagnosing this correctly, and 2) I'm not sure about how to proceed. I know the theory, I know how carbs work, but there's a difference between knowing the theory and actually doing it in practice.

First, does this sound like the likely reason for this new hesitation? Second, how would you recommend I proceed to find and fix the problem?

Thanks!

 

did the pipe come w/ tuning instrucions? like maybe turning the air screw or rejetting it. i beleave you've hit the nail on the head w/ your diagnosing. i know on my vmax which has suppertrapp muffles(same thing as white brothers w/ the disk) i went as far as i could w/ the disk w/out rejetting so it might be just that. cold weather would play into this as well.

 

i would think you would need to re-jet for top performance , not sure what way to go... i am thinking of a aaen exaust, polaris doesnt make a exaust for my little 400... i am very sure somebody here will have your answer

 

Nope, no instructions on changing the carb. Installation, repacking, and adding/removing disks - that's it. A single sheet of paper.

 

i'll try this to see if it works. jetting specs. on e series this what i found on white brothers site.

 

Idle air screw needs to be opened-just a 1/4 turn at a time til it gets better

 

That document from White Brothers says "stock" all the way across, implying no changes are required. I'm still confused.

 

Thanks! I'll check my service manual to see where that's located on the carb.

But this implies more AIR is needed. If the airflow restriction has been reduced by a better muffler, wouldn't that imply that my mixture is getting LEAN, and that more *fuel* is the solution?

 

Its actually a fuel screw. It needs to be turn out to richin up your pilot circuit. To me it sounds like your lean on the pilot and richin it up should cure your problem.

 

Backing the screw out adds fuel-your opening a circuit allowing more fuel to get by-richening the idle and off idle performance