Pretty much like I said, for GNCC and casual woods riding, you wouldn't want much more than the stock spring. You want to ourtun piped Raptors and Banshees in a dragrace, its not going to happen without a spring change even if you have duals, cams, etc. unless you keep the race VERY short. The stock spring shifts a mile too soon for even the stock pipe, much less an aftermarket set of duals. I proved that when I went from getting crushed by my brother's Banshee with the stock spring to losing by just ONE quadlength with a simple change to the Polaris brown. When he said the DMC's slowed the quad down, I knew he had to be running the stock spring because mine with the HPD plain and the DMC's will flat-out fly in a straight line.

I would be a little shaky about buying the Duncans if you are serious about drag racing. I would guess that pipes that work well with the stock spring are going to be at a disadvantage against pipes that will work well with the HPD plain or Hotseat blue springs. For the guys that don't like the stiffer primary springs, the Duncans would seem like the perfect choice.

 

I have the Duncans and have tried them with various clutch springs. I don't have a good side by side comparison vs. stock spring, but I do know that my buds modded raptor was beating me with a passenger on the back when I was stock! When I put the duals on, I installed the hpd silver/gold, 148/152 jets, removed the airbox snorkel, and dry wiped that raptor at both 200 and 400 ft. The raptor is now broken down and I have no local challengers[img]i/expressions/face-icon-small-sad.gif[/img] I now have 160/165 jets with the airbox lid propped open, but I don't have anyone to race. Maybe when he gets the raptor running again I'll try him with the stock spring then switch to either hpd plain or silver/gold and see what happens. The duncan pipes are very loud at wide open throttle, pretty tolerable otherwise.