Clutching -- Where do I start?
Correct Air Fuel Ratios are a must before you can begin clutching.
Focus on the primary and getting your engine rpm right. Your combination of clutching should take you right to PEAK HP and create continuous acceleration from bottom to top. In the primary (drive) you'll increase or decrease the weight and or profile of the flyweights to achieve this. Lighter weights reduce "grip" or "squeeze" and raise the rpm. Heavier weights increase the "grip" or "squeeze" lowering rpm. Heel = bottom end, Middle = Mid-range, and Tip = top end. Make sure you're using the same profile of weight when you make changes or you'll end up chasing your tail. High profile weights apply force quicker and flat profile weights apply force slower. Large rollers tuck the weight into the weight pocket and decrease the weights leverage or initial force. Small rollers untuck the weights and increase the weights leverage or initial force. You want just enough "grip" or "squeeze" on the belt that it doesn't slip.
Once you have your rpm where you want it your next job is to get the combination to shift the way you want it to. That's the job of the secondary. The combination of spring and helix is what determines your rate of shift either up or back. The secondary spring directly equates to side-force or "grip" or "squeeze" on the belt. The idea is that the more side-force you have on the belt the less efficient it is because of belt drag. You want just enough "grip" or "squeeze" on the belt that it doesn't slip. Too much pre-load, side-force, and the clutch will back-shift too fast, put you in too low of a ratio, and overrev when you stab the throttle out of a corner. All rpm and no GO !!! Too little and it won't back-shift fast enough, it will react sluggishly, or bog out of the corner, or lose rpm while trying to maintain high speeds. For the climbers you'll lose rpm while climbing. If your shift rate is where you want it DO NOT use the secondary to adjust engine rpm. I've seen a lot people use an increase in the pre-load, side-force, of their secondary to bring up their engine rpm, myself included. You are shooting yourself in the foot !!!! Once you go past the balance point it will decrease the efficiency of transmission of power to the track while adversely affecting the ability of the secondary to keep the shift curve flat. Lastly, I'm a believer in running the lowest gearing possible and still make the mph you're looking for. Gearing is a great way to increase out of the hole acceleration (torque multiplier). Its less work for the clutches, engine, and they will both run cooler.
Common Pit-Falls: Clutches MUST be clean. Clutches MUST have the correct side-clearence, deflection, offset, and center-to-center. Bushings MUST be serviceable. Springs MUST be within tolerence. Belt MUST be cleaned before break-in and within tolerance after. If all of these conditions are met see below.
Only change ONE thing at a time. Take good notes, like snow condition, temp, elevation, terrain, what you changed, and the effect it had. The primary (drive) and the secondary (driven) will directly effect each other. Try not to over compensate one to "fix" the other, it's a BALANCE you're looking for.
Note:
What works for boondocking/hillclimbing will not work for drag racing and what works for drag racing will not work for boondocking/hillclimbing.
Under target rpm.
1. Too heavy primary (drive) weights.
2. Too low finish rate (drive) spring.
3. Too steep secondary (driven) helix angle.
4. Too low tension in secondary (driven) clutch.
5. Too tall gearing.
Over target rpm.
1. Too light primary (drive) weights.
2. Too high finish rate (drive) spring.
3. Too high tension in secondary (driven) clutch.
4. Too shallow secondary (driven) helix angle.
5. Too low gearing.
