Secondary clutch change, what would new belt length be?

[riotwarrior]

I'm considering some changes to my SECONDARY clutching, namely from the 8 1/2" SPEED clutch to a larger diameter TORQUE sensing clutch like ya'll likely have.

So If I go from;

8 1/2" diameter to a

9.8" Secondary clutch 3/4" bore Part # 302604C

Or

11" Secondary (860) 3/4" bore Part # 300707C

What would be the respective increase in belt lengths be?

Thanks

Al

[riotwarrior]

Did a trip along a long uphill gravel road today, and I've got to say wow, this unit's clutch sucks. It's constantly working too hard as it won't gear down it always wants to gear up. I can get it rolling with decent rev's and then it just starts to bog it as the secondary opens up once it is running.

Thus I've got to get a secondary clutch soon to alleviate undue stress on the engine and get some slightly lower gearing.

I'd also like to know what the changes in clutch sizes will do for gearing from

8.5 tp 9.8 = what percentage of gear change?
8.5 to 11 what percentage??

I'll have to raise the transmission a little if I swap the 11" clutch but wow, what a low range!

I currently have what appears to be a 700 series primary however in time I'll go to a 780 series...

Please, help me figure this stuff out.

[LarryW]

I'm not sure if there is some fancy math equation to figure the belt length. Probably is. But what if you just drew it out on a large piece of paper. Crude but should work. Lol. If you knew the measurement between the shafts and the represented low range diameter of drive clutch there probably is a belt length calculated online.

[thebuggyman1]

The belt length math would be easy with 2 equal sized pulleys. The fact that the pulleys are far from equal and the unknown center to center distance makes calculating it very hard due to not knowing how far it would wrap around each pulley.
If you want "close" on ratio change, just calculate the change in pulley circumference (Pi times diameter). It wont be exact because of the interaction between clutches, but should be close enough for what you are doing.
After deciding on a clutch, you could cut your old belt, wrap it around the clutches and measure how much too short it is.......= new belt.

[LarryW]

You can Google belt length calculater and find lots of help. Here is one.

Belt Length Calculator

[riotwarrior]

Larry Thanks for link.

On my phone that link shows but I can't see nothing worth while to work with, on the puter this AM it's a whole different ball game.

I'm really seriously considering the 11" and a new 780 comet primary with spring pack for 1075 RPM engagement. That primary is for the diesel. I cannot get my primary off my Tecumseh not no way no how, so I'm stuck with it for now.

What size secondary's do you fellows have/use? What gear ratio spread can you acheive? Under/over drive ????

[ARGOJIM]

If you are still running the stock 2 stroke clutch, you could change the spring.

[riotwarrior]

If you are still running the stock 2 stroke clutch, you could change the spring.

This 6x came with factory 4stroke the engine I'm running however it's a SPEED clutch not a torque clutch...it's a POS IMHO constantly trying to go up and never down unless you come to a complete stop. It has been cleaned and reassembled by a snowmobile mechanic who says he has never seen a clutch like this and how it functions.

Just saying it's a POS is all...and I need a different clutch.

Thanks for the tip but no change will affect this unit IMHO as it's not designed for this application.

[ARGOJIM]

I think the Polaris 4 stroke clutches are 8-3/4 if that helps, there are plenty out there used. Perhaps JerseyBigfoot or Spookum can help with a series. Along with the calculator should get you close.