Clutching Question

[Blackhawk]

Has anyone ever tried to use the Axys 800 clutching on their Pro 800? I noticed the helix is a different angle on the Axys, the Pro uses 56/42/36 while the Axys is a straight 40. The primary spring is also different, the Pro uses a 140/330 while the Axys uses 120/320.

Finally, I am running the BMP 800 durability kit which is supposed to improve horsepower so I would think the power output on that is similar to stock of the 800 Axys. My Pro is old enough where I want to do some clutch maintenance anyway and curious if calibrating it to the newer setup while I'm at it would provide any performance advantage.

Thanks!

 

[Alpine Xtreme Edge]

The 56 is the starting angle of the pro helix. Your in that 56 portion for the initial part of upshift. As it upshifts, it transitions into the 42 angle portion for the remainder of shift out. The higher the number, the more the clutching loads the motor and the faster it upshifts if the motor will take the load.

I believe the straight 40 helix works in the axys because the lightened crank and rotating assembly is able to rev quicker. The 40 makes the axys power delivery manageable for the masses, but going to a steeper initial angle makes them even more snappy in my opinion. Going to the 40 in a pro engine would go backwards in terms of response and upshift speed.

As far as the spring is concerned, the first number (140) is the starting pressure, and the second (330) is the finish pressure. What that equates to in terms of comparison to the axys spring, is that the 20 lb less starting pressure of the axys spring would lower your clutch engagement rpm. Again I believe it works in the axys because the lightened assembly revs quicker, thus as the sled begins to move, it's probably at a similar rpm as the pro.

The finish pressure is how much spring force is working against the clutch compressing as it reaches full shift out. The higher the number, the higher your max rpm as the spring is limiting how fast the clutch can compress the spring and upshift which raises max rpm. Going 10 lighter on finish pressure would lower max rpm.

On your pro clutching, I would replace bushings as needed and new oem pro springs if you feel your originals are sacked out. And if your looking for a bit of an upgrade, get a helix with a slightly steaper initial angle (60/42-.36) as it will give you a bit more bottom end response and punch out of the gate.

 

[BeartoothBaron]

^ Hit it pretty well. The AXYS 800 is a different motor, so blindly mimicking the clutching is likely to make things worse. One thing I would suggest is gearing down, and with that you can probably go to a spring with a lighter start – will give you a little earlier engagement, which should make it smoother without causing issues because the motor doesn't have to work so hard to start the pull with lower gearing. There are a ton of old threads on clutching, so you might want to look through those. Copying a good clutching setup for your sled (getting as close as possible on track length, mods, typical snow where you ride, and elevation) will almost certainly do better for you than trying to copy the AXYS. Also, you've got a couple good options if you want to buy a custom setup based on your sled and riding.

 

[AdrenalineAddict]

I played with the clutching quite a bit on my Axys, even experimented with the 56/42 from my pro. I never could find anything that performed better all around than the stock clutching with the straight 40. It drag raced very well, held spot on RPM's in harpack hillclimbs, had adequate backshift and RPM's in steep powder climbs, never fell on it's face running 10-62's. The only issue I ever had were those hot springtime days at 10,000' where I would have to run a 130/340 to maintain 8,000 R's. I rode and raced dozens of other 800's with supposedly superior clutching combinations, some ran well, but none ran better.