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9 Posts
Discussion Starter · #1 ·
I’ve been experiencing a series of belts exploding on my 2005 M7. Before spending yet another $100 on a new belt I would sure appreciate any suggestions on why this might be happening and how to fix it (or have I just had a series of bad belts). In all cases it has been the recommended Arctic Cat Belt (part #0627-036)
First Instance: Feb 2005 going up the trail at Sicamous B.C.
- belt had several months wear
-68 gram weights
-approx 4000 feet
- going wide open throttle on a straight stretch
- secondary pretension set at 0.43” per recommendation from Salmon Arm AC dealer (was less previously)
Result: Belt exploded. String wrapped around secondary and took an hour to remove

2nd Instance:
- installed Sled Junky kit and Cutler Adjustable weigths. Ran it in the mountains on 4 day trip at 5-7 thousand feet and several trips around home at 2000 feet. Checked clutch alignment (offset and parallism) – was good. Belt deflection set to spec (1 ¼ inches) No problems except noticed I was over-revving around home (8100 RPM)
- to correct this I maxed out the Cutler weights to 74.5g by installing the 1.39g set screw in the toe position of the weight (empty before) and the .78 + 3.05 + 4.25 screws in the main shaft (plus the 65g starting weight of the cam)
- I noticed the pretension adjuster on the secondary had completely worked its way out. I cranked it inward to about .5 inches (may have been a bit more)
- put brand new belt on (had washed it thouroghly previously)
- went for a ride. After keeping it slow to break in the belt (perhaps not long enough as I was impatient to see the results) I punched the throttle (wot) back and forth on a ¼ mile to 1/3 mile stretch in a field. On the 4th pass the new belt exploded. Failure was just like before, pieces everywhere and string wrapped around my secondary

Third Instance (today)
- put on an old belt. Not bad shape but had the edge string gone for a few inches on one side (hey I’ve used similar before with no issue).
-I turned the secondary pretension adjuster undone almost all the way out (I thought this was the CULPRIT), ie: as least amount of pretension as possible. Belt deflection per spec.
- after ½ hour of operation, going wide open throttle on a straight stretch and I heard a sharp ripping noise. I immediately stopped, checked the clutch and the $%$#@!!*(&
belt had blown. This time it had not totally exploded, but the outer half of the belt was sheared totally off the inner, at the place where the string is. I limped it home.

Analysis at Home tonight:
- checked all the clutch alignment several times. Totally within spec
- the secondary spring tension was almost totally turned out (least amount of tension as possible)
- there were streaks of approx black 4/5 of the way up the primary. This was not normal but I do not know if was the due to the explosion or somehow indicative of the cause.
- everything else looks normal

I am not sure what to do. Could it be that the first two belts blew because of the spring tension adjustment (perhaps combined with the tighter springs of the Sled Junky kit) in the 1rst and 2nd instance, and I just had a bad belt in the third instance? I’m looking for advice before I try it again.

Thx in Advance,


69 Posts
Ride your sled slow or easy for a little while then feel your clutches they should be about the same temp to touch if one is obviously warmer or extremly hot then your clutches are out of alignment, causing the belt to slip on the hotter clutch and blow the belt. Basically they are not working together

9 Posts
Discussion Starter · #3 ·
OK I had posted this on several forums and got some very good suggestions back (thanks!).

I checked Offset and Parallelism clutch alignment per the ’05 shop manual (CD I purchased from AC) section 8-29 using the AC clutch alignment tool part # 0644-427 (1.655 offset).

I thought both looked good:
Offset was about .7mm or ½ the max distance allowed (1.4mm) from the inside edge of the stationary . . . however I am no mechanical expert and was not exactly sure of the technique to measure this (used a spark plug gap measureing set)
Parallelism at points X (rear) and Y (front) of primary were identical (1 and 5/16 inches)

HOWEVER, I did notice something new. The INSIDE of the sheave of the primary has a very distinct and consistant dark mark at the very inside outer edge of the sheave approx 3/8 inches wide. There is no way this is right and I’ll bet it means my clutch (offset?) is indeed off. Does this sound right? Pic attached below

I confess that when I put my SledJunky kit on, I had taken the secondary off and taped the shims on the shaft of the sled to keep them from falling out (did this over the summer) and then, when I put the secondary on, there was another shim that I thought fell out of the loose secondary that I had missed. . . that I put on when re-installing the secondary. Could it be as simple as I have too many shims on the secondary? Would this account for the black ring on the primary? (probably given my “skill” and luck as a mechanic – LOL)

Please let me know what you think and thank you very much for the responses (past and future)

Winterbrew, I’m intrigued by your comment “Also, the DD secondary hates tip weight on the primary arms.” as this is the other thing that changed for Instances 2 and 3. Any chance you could elaborate? Thx.


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