Belt to sheave clearance

Rixster

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I am looking for a little info here. All of the sudden with a Brand new belt I have to adjust my deflection out so far that sled would be in 4th gear. With a used belt, I can adjust the deflection so the belt is sitting in the right place, but when the sled is cold it really doesn't want to grab the belt from a dead stop. I was trying to picture it in my head, do i place shims between the sheave and the spider or is there shims under the sheave? Ever since I bought this new primary it hasn't performed like it should from a dead stop. I figured since it was the proper part number clutch from cat for the sled that I wouldn't have this issue.
 

Thunder101

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Your belt to sheave should be .020 with a new belt. Cat uses a step shim and you will need to have it machined down on the small end usually and then shim the big end to untuck the weights
 

RACINSTATION

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The shims go between the fixed sheave and the spider, so under the spider. Like Thunder said, a lot of times they use a stepped shim. Sometimes a shop will rebuild a spider or a clutch and check the belt to sheave clearance and set it at .020", which is Cats recommended spec, and they will neglect to measure the weight to roller clearance. The stepped shim allows the moveable to travel a bit farther and keep the weight close to the roller so you don't get a slap in engagement. Also, if the roller to weight clearance is insufficient you will get belt drag even if you have proper belt to sheave clearance.

Most new clutches are close, but many are way off. If your clutch is shimmed too wide, so it engages high or the rpm must be too high for it to start to grab the belt, honestly the easiest solution is an ABC kit, then you can adjust it in nice and easy without dis-assembling the clutch and as the belt wears, you can tighten it up and get better belt and clutch life. The ABC kit will cost about the same as what most shops would charge you to shim the clutch.
 

Rixster

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It seams to me that the sheaves are to close to each other. Is there a spec that I can measure the distance between the sheaves right at the center shaft?

Also, where do you measure belt to sheave clearance? Is the belt supposed to sit on the center shaft? If so my sheaves are way to close to each other.
 

Thunder101

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Maybe it was for a chain case F7 ?
And yes to check belt to sheave you bottom out a new belt and check clearance with a feeler gauge.
 

Rixster

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Maybe it was for a chain case F7 ?
And yes to check belt to sheave you bottom out a new belt and check clearance with a feeler gauge.
Well, that's the issue then, I am pretty sure if I pushed the belt as far down as I could it would still be 3/4 inch from touching the shaft. Thank for info guys. That gives me something to do this weekend since our snow here SUCKS !!
 

jakim

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Just wondering what weights you are using. I had to modify my Mds weights when I got a new clutch. Steve modified them for me to allow the shivers to open.
 
Mar 1, 2008
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I agree with Racinstation, and i notice than when i add a shim for get a better roller-to-weight clearance is the way to go for a better/smoother/lower engagement and better belt grip, so i add 0.030'' shim at every primary that i rebuilt or for guy who need a smoother engagement... and they are always happy!
 
Nov 26, 2007
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Well, that's the issue then, I am pretty sure if I pushed the belt as far down as I could it would still be 3/4 inch from touching the shaft. Thank for info guys. That gives me something to do this weekend since our snow here SUCKS !!
If you are that far from going to the bottom there is something else going on. What weights are you running? If they a slp's mtx or mds weights you will have to make some changes so they don't bind.
 

diggerdown

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Back the cover bolts off so you know your weights aren't causing the issue, if it's not the weights then get the ABC kit and go ride! I've never seen a clutch that far off from the factory. I know some of the after market weights need to be ground down to fit. I would not pull the spider to shim it, too many issues with the high heat it takes to break them loose.
 
Nov 26, 2007
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Back the cover bolts off so you know your weights aren't causing the issue, if it's not the weights then get the ABC kit and go ride! I've never seen a clutch that far off from the factory. I know some of the after market weights need to be ground down to fit. I would not pull the spider to shim it, too many issues with the high heat it takes to break them loose.
The ABC kit will not fix it if it is already too tight.
 

RACINSTATION

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Correct, the ABC kit will only help if it is too loose. Too tight, you gotta break her down.
 
Nov 26, 2007
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If you are running a lot of tip weight and the set screw is protruding from the end of the weight it can bind on the spider and keep the clutch from opening all the way and cause your problem also.
 

Rixster

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I rebuilt the spider with new rollers, pins and buttons, removed the 2 spacers between the spider and the sheave. Now the problem is worse. With no weights in the clutch its still to tight. With weights in the clutch the is so tight that even the old belt is was running is to tight. I guess the new rollers with zero slop tightened things up. So, now what? Pull the sheave and have .040 removed? got to love cat clutches, just another reason I cant wait till I can buy a XM.
 
Mar 1, 2008
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It's normal you removed a Spider shim(big shim), you dont remove Sheave shim (small shim). Reinstall your big shim, watch for a shim with same outer diameter that shaft where moveable sheave slide. If you dont have it, you will need a ABC kit
 

Rixster

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I think that is the issue here, there is no sheave shim. I think i need a shim or 2 for the sheave and a couple for the spider.
Good stuff, maybe I can get it fixed today.
 
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