On my gfs XC 500, between 4000-4600, the sled kind of pops/burbles and then hits about 4800 at 1/2 throttle and the sled takes off like a rocket. We're talking skis off the ground kind of take off. The sled has PLENTY of top end, hitting 95mph on the speedo with ease.

Things I've found:

- O rings leaking on head, replaced all 4
- Carbs a little dirty, cleaned them both (stock jetting @ 370 jets)
- One reed was installed backwards, we flipped it around
- Oil pump extremely rich, adjusted it
- New plugs as old ones were oil fouled
- Incorrect belt on the sled, now has a 3211074 as per pockets recommendation
- The belt was way down in the secondary, we disassembled it, cleaned it and put it back together and adjusted the belt height

Does anyone have any other suggestions? We didn't have a set of 360 jets, so we tried some 350s and it was a little on the lean side so we went back to the 370s.

I haven't done anything to the primary yet. It's all stock as far as I know, and probably the original springs/weights etc. The sled was TERRIBLE this past weekend, and needed more than 3/4 throttle to have any response at all, it's much better now, but it's still there.

Any suggestions would be appreciated.

Raise the jet needles one clip, try it, then lower the needles one clip from where they were, try it. Let us know what it does.

360 mains
needle #2
I tried a boost bottle on mine and it did clean up the low end burble, but I think it hurt the performance.
I suggest playing around with the air screws and installing a set of boyseen power reeds. Reeds really wake it up in the low to midrange.
I thought the factory clutch set up was near spot on on this sled. Spring replacement is possibly overdue. Also check out the nylon bushings in the weights for out of round.
8250 is optimum rpm falls on its face after that.
Hope this helps. :div20:
Miss my 99 pure rocket. Burnt in a garage fire.