skidoomaster, I have a regular 670 w/ 42.5 carbs, ported, 0.060 head, gutted air box, 501 RV, shorty boots, y pipe mod, timming redone, 25/44 gears, 1.18 full lug track, original clutch setup helix 50, sec. at 19 pounds, clicker at 5, 286 ramps. I have part of Cudney's clutch kit on except for primary spring which bumps engagement to 5000, I was waiting to doo a break in befor installing it. I will probably try your setup since my 670 is now performing like an HO and probably even a bit more. What's your top speed with that setup ? How much do you weigh if you don't mind me asking.