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Machining a 10" secondary to 10.4"

PowerJoe

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Jan 9, 2008
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I am going to convert my 10" secondary to a 10.4 by machining the sheaves. All I could find on this forum about doing this was from Barrett as seen below.

to mod a 10" clutch, simply have .055" machined off the bottom part of each sheave, where they touch together when the clutch is fully closed. you may also have to grind a small portion of the lip off of the gold spacer shim that is directly under the helix( I had to). you then need to run a longer belt - find 1 that is 46" long, and 1.440" wide. I like the pol 1099, but cat's 046 fits too, as that is the stock belt for a m sled with a 10.4", there are a few others as well.
lastly to make it all work, you need to remove a .060" shim from behind the sec clutch(compared to the cat alignment bar), because when you get the deflection right, the belt will be hanging 3/8" over the top of the sheaves, and since the belt has a tapered side, it is effectively further to the outside compared to when it sits flush in the sheaves.....make sense?
this is an old flat lander trick for snow-drag racing, but it can be appyed to alot of applications. It works especially well on the 10" DD secondary's because they have such a small diameter at high shift ratios, and full shift ,that they have little belt side contact,and suffer ALOT of belt slip.
the cut clutch allows the use of a longer belt which stays out of the large OD ratios dsigned into the DD secondary.
overall - it efectively gears down the sled(max of aprox 10%od acheivable after mod), and gives the belt a fighting chance at survival when at high track speeds. this also shows why the DD secondary clutches respond favorably to STIFF secondary springs.

Has anyone else done this and is Barrett's info acurate? Wouldn't I want to machine .060" off of each side as the shim I am adding is .060"? I guess .005" probably doesn't make much deference. So if I machine .055" off of both sheaves where they come together down by the shaft, they will be closer together by an overall of .110", right? I am just worried about machining too much material away and loosing sheave surface on the belt when the clutch is full shifted out. For example, once you make this mod there is no going back to using a 036 belt as when the clutch is fully shifted out the belt would no longer be on the sheave surface. It would be wraped around the shaft and belt would be pinched by two veritical walls.
 
M

mtn_extreme

Well-known member
Nov 11, 2002
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Nampa, Idaho
I cannot see this working as the problem with the 10" sheaves is the small diamater at WOT that the sheaves have to grip the belt. Slipping is the problem with the 10" and making it smaller is going to slip worse. The 10.4 sheaves start out taller and WOT doesn't let the belt go so far down in the sheaves for more surface to grip.
 

PowerJoe

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Jan 9, 2008
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You have to run the 046 belt with this mod as the belt is longer and will initially sit higher in the sheaves and then not go down as far into the clutch just like on the 10.4. You will loose a little belt to sheave surface at clutch engagement, but at WOT it should be identical to the 10.4. I know this will work, I just want to confirm the measurements before I cut metal. I had talked to some drag racers a few years back that also did this before the 10.4 even existed.
 
S
Nov 27, 2007
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10" to 10.4

I bought on that was machined.it looked like both faces of the secondary where done.I was able to run a 36 belt with the right shims.Or 46 again with the right shims.I thought I would give it a try because on my 10" the splines where worn causeing a nasty clunk!.Good luck.
 

G-Force

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Assuming you'll be taking your clutch to a machine shop to have the work done, I would think that you could pretty much buy a set of sheaves for awful close to the same price as the work. I know up here we are cheap at $105.00/hr (Cdn) and would think any machine shop (not counting a buddy etc) would have a minimum charge of at least that. What are a set of sheaves these days? $180 ?? So if it takes Ernie the machinist an hour and a half, yer pretty much splitting hairs... just my take on it is all. Now if you have access to the tooling/a buddy that does it for beer, would work out for ya I'm sure :D
 

PowerJoe

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I have acess to a lathe for free or maybe a few beers and I plan to do 2 or 3 clutches at once. I am not only doing it to save 3 or 4 hunderd dollars but I also like the added clearance that the smaller 10" sheaves have in the M7 chassis.

I actually ran a 10.4 in my M7 last week and it worked great but I had a problem getting the exact alignment I wanted. If I removed all of the shims from behind the 10.4 the alignment was correct, but you could not fully tighten the clutch to the bearing inner race on the splined shaft. The shaft was too long and the clutch was loose with the bolt tightened so I had to run at least one .030" shim to get the clutch to clamp tight.

sledbasher M7 - I don't think you can make it a 10.4 by machining the sheave surfaces. You want the sheave surfaces to come closer togther so the belt rides up on the clutch higher. Not sure what you got going on with your clutch.
 
M
Nov 27, 2007
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Eagan, MN
First - This mod absolutely works - has been done to many 10" clutches since the came out in 2005. If a machine shop charges more than $25 - $30 dollars to perform this they are robbing you - it is very simple.

Second - If you don't like it, you can go back to the "old" 10" clutch, your belt never gets pulled low enough in the secondary to be impacted by the area you are cutting off.

Third - Must run a longer belt, 046 is a good one, I am running XS belt equivilant.

Fourth - You will also need to remove the foam that is on the bottom of the clutch cover. Your belt will be running pretty high in the secondary at take off and it will rub this if it is not removed.

When I first got the sled this is one of the first things I did. Other things were a stickier belt (XS works well), lighter weights, decent secondary spring and correct the horrible primary belt to sheeve spacing that existed in '05. With a stickier belt and lighter weights you do NOT need a gorilla secondary spring to make a compression spring set-up work. I am running at sea level with 68'ish gram cutler adjustable weights. In deep powder she holds 7920 rpms all day, very low clutch temps. From 0-60 (with some snow)it will beat my F7 SP which has performed well at many ice drags. You can make these sleds really perform - the 10.4 mod is part of the equation. Good luck. Paul
 

Blk88GT

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Joe, please let me know how this works for you and what you end up doing. I would love to get this done to my clutch for the same reasons you are doing it over changing out the sheaves.
 

PowerJoe

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Paul - Thanks for the info!:D

Can you remember how much you machined off of each sheave? Was it .055" like Barrett had stated?

Glad to here you can still run the 036 belt if you had to as a backup. With 3 of us guys doing this we will only have to buy 3 new belts at first and not 6. I will just carry extra deflection adjuster shims in my tool kit so I can switch back and forth.

I will eventually switch to the XS belt to someday as I can get a deal on them and I like the concept of a stickier compond and cooler running clutches.;)
 
M
Nov 27, 2007
33
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Eagan, MN
Power - I honestly don't remember what I shaved off in the end as I did mine over a period of time and played with it. 0.055" per sheeve does sound about right though - there is a "brass" colored bushing that also needs to be machined - you will know what I am talking about when you have the clutches apart.

Certainly no issue with the old belt - just make sure you have enough shims to make it work.

When you switch to the XS belt - you will need to drop weight. Changing nothing else I had to drop almost 3.5 grams. In the end I made other changes that caused me to lighten up even more (lighter secondary spring than most are using). The single biggest improvement (IMO) is the stickier belt.

Good luck with your project - I'm pretty sure you will like it. Paul
 
M
Sep 16, 2008
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0.050 Should do it. I machined a 10.4 to go with an even bigger belt and i took about 1/32 (0.0312) off each side. I get proper deflection with the adjuster almost out, probably could have taken off a little more.
 

kej

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Dec 1, 2007
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What belt did you go with the 10.4 clutch machined .0312 off each side?
Thanks
 
M
Sep 16, 2008
95
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XS809 is the number i think. Fits polaris dragon anyway. Its 5/8 longer then the normal 10.4 belt. You need to install the little drop down pan in the belly pan off the newer sleds and bend the clutch guard/footwell area a little bit but it does work.
 

PowerJoe

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How well did that work for you? Was it a similar improvement like going from the 10 to the 10.4? Is that the same belt size you would run on the 11.25 clutch?

I heard from a guy that he didn't like the 11.25 set up as he lost his overdrive. Ended up with less than a 1:1 ratio. Not sure if that is true.
 
M
Sep 16, 2008
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I havent put enough miles on the sled yet to say for sure, plus only time i rode it stock was from the trailer to the shop. I've been having some engine trouble and lack of snow isnt helping.

It has to work if you think about it. Its the same concept, just taking it a little further. Probably do loose a little more overdrive but its not the end of the world. Still more overdrive then a chaincase sled. My only complaint is the belt is borderline too long for the setup. Have to run it way up there to get proper deflection. I might try to find away to bring the center distance apart a little bit to correct this.

Is there an easy method to adjust center distance on an 05 M series? Seems like my engine has more backwards movement then id like to see too. Was nice and solid in terms of center distance on my old Firecat. I havent really had the time to look at it yet, clutching is ok so other areas of the sled are priority for now.
 
W

Wood

Well-known member
Dec 7, 2007
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I did this mod for my Crossfire and it works well. 55-60 thou of each sheave and your good to go. You may want to get a BDX deflection adjuster as the AC adjuster needs to be stacked full of shims (past the o-ring) to get proper deflection. If you can't get the right offset you could also machine 30 thou off the inner collar on the back of the clutch that's sits against the DDrive, just be sure the outer collar doesn't rub the DD case.
 
F

fradiecat

New member
Feb 14, 2008
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I drew it up on CAD before I cut mine.
.050 is the # to shoot for to make the 10.0 into a 10.4
 
Last edited:

PowerJoe

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Jan 9, 2008
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Thanks guys!:D I am machining the first one tomorrow. I will try to get it on the sled this weekend and give a report on how it went. Maybe I will even take some pictures.
 
F

fradiecat

New member
Feb 14, 2008
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Even though .050 blends the 2 diff. sizes when I drew it up in CAD,
The 046 belt sure seems loose. I can almost squeeze the belt together
between clutches and make it touch.
Maybe another .010 off each side?
 
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