Arctic Cat M8 secondary clutch modification

[zmotorsports]

I had another Arctic Cat M8 secondary clutch come in the shop over the weekend so I decided to photograph the modification.

The problem is the poor design of the new Arctic Cat secondary clutch on the Diamond Drive systems. They use small 10-24 X 1 1/4" button head torx headed screws that are notorious for breaking off as well as not being very convenient when it comes time to swapping helixs for tuning. You cannot simply install a socket head cap screw due to the clearances involved between the back of the secondary clutch and the DD system.

I cannot take complete credit for this modification as I had heard about it several years ago from my local dealership. I have performed this modification on a half a dozen or so clutches over the last couple of years and decided to do a write up so if anyone else would like to perform the same modification. I chose to use 10-24 X 1" socket head cap screws and countersink them 1/4". The clutch is .650" thick so even after countersinking .250" there is still .4" remaining for plenty of strength. Mike.

Overview of parts:

Stock screw on right, new on left:

Sheaves after cleaning and surfacing, ready for modification:

Clamped on the mill table:

Precise measuring to find dead center of the hole for alignment:

First hole completed:

Last hole completed:

Completed, removed from mill:

Test fit:

Completed, all bolts installed:

 

[jhelrey]

Nice! Never would have thought of that!

How well does it stay balanced?

 

[zmotorsports]

Nice! Never would have thought of that!

How well does it stay balanced?

Fine as long as you remove the same material from each hole. This is mainly why I suggest you perform this modification on a mill rather than a drill press, so you can remove the same amount of material very precisely. I suppose if you were to set up a dial indicator and was very careful a person could perform this with a drill press.

Also, the holes are very close to center of the clutch so less effect than if they were further to the outside diameter. Mike.

 

[lametec]

Why use a dial indicator for finding the center of the hole? A center finder would be easier and quicker, no? I don't think you need tenths precision here.

Obviously, a dial indicator will do the job, but just wonder why it's your choice of tool.

 

[cnc-me]

Thats a drill press job for sure, as you are not drilling any new holes,
only counterboring existing ones.

Oh well, there's always at least two different ways to do any job.

 

[zmotorsports]

Why use a dial indicator for finding the center of the hole? A center finder would be easier and quicker, no? I don't think you need tenths precision here.

Obviously, a dial indicator will do the job, but just wonder why it's your choice of tool.

Probably because I am not what you would call a 'seasoned' machinist and I wanted to be absolutely sure the counterbore was centered prior to making chips and it didn't take much more time than the center finder. Mike.

 

[zmotorsports]

Thats a drill press job for sure, as you are not drilling any new holes,
only counterboring existing ones.

Oh well, there's always at least two different ways to do any job.

The reason I chose the mill is because I can accurately measure the depth to the thousandth whereas on the drill press it is not as accurate. It was also easier for me to bolt the work securely on the mill table vs. the drill press table and move from hole to hole. Mike.

 

[lametec]

Fair enough. Whatever gets the job done. But I can't help but think that idicating in 9 holes with a dti would take a lot longer than using a center finder.

With a center finder, just stick the tip into the hole and feel around the lip with your finger. Adjust as necessary. Should take all of 5 seconds per hole once the tool is in.

This only works if the hole isn't too big for the tip of the center finder, of course.. In your case it appears the holes are small enough for this technique. Not as precise as a DTI, but you'll easily be within less than a thou of the center, and that should be close enough for what you're doing.

BTW, I'm no seasoned machinist either. Just bought my lathe and mill last year.