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Post by olyman on Feb 14, 2021 23:40:47 GMT
I noticed today that the 71 640 tnt has a squeaky and worn out driven clutch. Has anyone ever swapped the sheaves out with something a little newer? Definitely inconvenient with the brake, but surely someone has modified these before. It would be nice to get something that can open up further, as the powerbloc primary clutch I have has more movement than an oem clutch. I am not opposed to swapping out the whole assembly for something newer if it would fit. I always keep old stuff on the shelf in case I want to go back to OEM.
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Post by olyman on Feb 19, 2021 14:12:54 GMT
I have the secondary completely out and seeing about fitting a 72/73 style aluminum case. It looks really close for alignment but not sure its the right idea. I will need the spacer behind the case I think. I realize the 72 wide bodies have an aluminum case but looks like they don't have the spacer. I'm guessing that means the case is deeper than a 440 style.
The aluminum sheaves allow the belt to reach higher and sink a little lower in comparison to the steel (at least 5mm+ vertically), which is what I want.
My new oil seal just arrived so I will see how I make out with it.
I'm still looking for a better steel secondary, but will keep pushing fwd with this aluminum one in the meantime.
Considering I don't have any new projects this winter, it's amazing how much time it takes keeping these old relics actually running well!
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Post by Doo640ER on Feb 19, 2021 20:22:42 GMT
Olyman, maybe just dig a little deeper, I find it difficult to believe you don't have what you need buried in your barn! LOL. Good job keeping at it, youve got more energy than I doo, at least today.
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Post by tompriebe on Feb 20, 2021 2:22:42 GMT
Well, I've played with a lot of Ski-Doo stuff, from 71 T'NT's to 81 Snopro's. The 72-73 aluminum chaincase is a plus. The stamped aluminum secondaries that came on the RV's suck. Go with the 72-73 chaincase, and an aluminum cast secondary from a Safari with a decent disk brake.
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Post by olyman on Feb 21, 2021 13:54:00 GMT
So I spent some time with this yesterday. The original steel chaincase is different than any case I have around here. The main differences are the bearing cup length and the offset metal thing that stands the case off the side of the tunnel. So it's very specific for an 18" chassis. All of the aluminum cases I have here (3 different styles) are not compatible. I am thinking that to make one work I would have to customize the standoff to be about half as thick, and even then wouldn't know what the actual resulting clutch alignment would be. Not to mention I would have to fab a mount for the stabilizer that the aluminum cases had on the outside of the secondary. Then I thought about adapting the newer styled sheaves to the old steel case, but to make that work I would have to cut the brake arm AND the adjuster bracket thing that you adjust the belt distance with, because the aluminum standoffs from the sheaves that hold the brake disc get in the way of all that.
So I decided to go back to the old steel one for now. I added a little more clearance from the chassis (to get better belt alignment) by cutting a piece of tubing. Ill grab a picture later to help explain. The moving sheave on this steel clutch is still pretty worn out, so I will be looking for a better one. Also added some skidoo clutch lube on the shaft so it wont bind hopefully.
So if you have a good steel 640 secondary hanging around (and within driving distance) let me know.
going to try out the new carb and setup I finished while I was at the clutch..
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Post by silverbullet on Feb 22, 2021 4:20:47 GMT
I feel your frustration! I know from experience it's a love-hate thing some times. In my own circumstance, I am set up to make or repair just about anything from wood. Yet I focus my energy on restoring/rebuidling/ reconfiguring things made of old rusty iron that run on snow...which only stays around for weeks at a time anymore, lol. If we had access to machining tools we could work up a correct spacer. How about a laminated plywood one??? Just joking of course.
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