I have 670 that I have done don emery mod's. Now after mods rpm's hitting 8500 the primary has 286 ramp with clicker set on 2 and yellow primary from cudney engaging at 4800 rpm. The secondary has the stock 47* helix with beige spring set at A 1 for 14 lb.s . The machine out of the hole to 140 km not bad but revving much higher than I like 8500 rpm. From 7000 up seem to be slipping is my secondary not set for enough spring load or do I nead heaver pin in my clutch.
Yup start adding and also start checking the clutch temps. Not sure what is the yellow spring, but you may find a spring with a lower end load also to bring it down. You are looking for a straight shift without the rpm's wavering. If you have access to some other cams get them to play with. What are you going to be doing with your sled? Hate to be too general about this. -Grover :hallo1:
you need to add weight to pin.
I would put in a 54/46 helix and then tune your primary for RPM
You will pull a lot harder out of the hole with this helix. I thought stock for the HO was a 53/47??? anyway.