Hi
I have some probs whit my ProX 800-03 it´s 10-66 and a silver spring!
I feel that somthing is wrong!
Can it be the spring that is to hard?

Thanx

We need to know your set up , where you ride (eleavation) , gearing track size and who makes that parts your questioning are wrong.

The onley thing that is done is

430 mains
23/40 gear
10-66
Silver spring

eleavation approx sealevel!

Who's the manufacturer of the silver spring, what's it's spec's. Polaris' silver spring way too soft to work in this application. Erlandson would be 165/300 or Hot Seat would be 165/310, etc. The stock spring would have been blk/grn @ 120/340, w/64g weights. If you don't know for sure what the spring is, I'd opt to change it to what I knew the spec's are, and then it would probably be a blk/wht @140/320 from the polaris parts bin, and stay with the 66's.

Also geared way to short for an 800, unless it's a long track.

Thanx U-Con The sled was set up this way when i got it so i dont know the manufacturer on the spring
have changed to a almond blue, going to try it after work today!
Do you think it´s good going back to stock gearing?

The worst thing I've seen, and others may disagree, but when you gear down an 800 (121") you slow down but more so they become a bear to get them to hook up, especially geared down that far. Unless, it's a 136", which it doesn't sound like you have. Also any 800 twin that I ride with around here gets between 12-15 mpg in full gear. If I had one on my trailer it would have a ratio closer to a 26/41.
Someone else on here, and I don't remember who at the moment, also mentioned about not going over 310# force on the more full shift end of the spring. It just seems like anything past 310 or 320# keeps the rev's up but stalls the shift.

I changed the gearing to 26-41
And the almound blue spring, was a improvment like now other :-)
I think the silver spring has 75/235-240 something and the almound blue 140/320
Anyway the sled is now shooting lika a ProX is built for :-)

Thanx U-Con

23/40 gearing for a 800 as a 121 is not that far off if your clutching is good. I run 24/41 on my xc-800

24/41 is 1.708
23/40 is 1.739