Join Date: Feb 2006
Location: Woodstock, Ontario
Thanked 28 Times in 26 Posts
Sled: 2001 Thundercat
10-11 Mileage: 1798 M
09-10 Mileage: 1800 M
08-09 Mileage: 1787 M
07-08 Mileage: 2120 M
06-07 Mileage: 1645 M
I own a new 6-post fixed pin clutch that I have on my 2001 T-Cat. The 6-post clutch is a better, thicker casting. The pulley sheeves are thicker and should be less prone to cracking. The movable half is very strong around the button slides and should take the hammering harmonics of the firing pulses of a two cylinder engine better. New for 2008, the cover bolts are thicker above the threads under the bolt head. This locks the cover to the tower better like a dowel pin and will eliminate the towers from spreading. The sheeves are machined and not just cast like the old clutches.
The old design of bushed flyweights and 1/4" pivot bolts is inferior to the new fixed pin design. The torsional harmonics cause the weight to wobble sideways and this just wears out the bushing so the weight gets looser and eventually hits the spider. The fixed pin weight is wider at the pivot. The hole is 5/16". The pivot bolt is 5/16" with a dimple to lock the weight set screw into. This positively locks the weight to the bolt so it cannot wobble sideways. The tower is bushed on each side to provide over twice the bearing support to the pin. The bushings is tefon coated bronze over steel and should last a very long time. There are viton "O" rings under the nut and bolt head to cushion the bolt to lateral movement.
New style weights are required with lock screws. Because the weight is wider at the pivot, that makes it heavier where the weight does not move. Because of this, you need a flyweight that is about 5 grams heavier than the old style. I am using 60 gram fixed pin weights where I used to use 55 gram bushed weights. There are also at least three different cam profiles and they are not documented. It is very difficult to pick a weight to use. I think A/C is calling the profile P1, P2, P3, P4 etc. I don't know the difference. There needs to be a picture profile map made like the old racing manuals had.
I would suggest using Dolton Pro adjustable flyweights if you can live with over 60 grams as the lightest weight. Look at the online parts lists for many different machines to get the weight part numbers and descriptions.
The extra total clutch weight will add more flywheel to the engine. It will be a little slower to rev and will coast more. However, this would be a very good thing for the old 700 Wildcat engine since it would damper the harmonics that tear the clutch apart on this engine.
2001 Thundercat ESR
Everything an Old Man needs.
Just joined the 20,000 mile club.