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Here ya go. Best thread ever!!!


Clutching

By request- I am new to this forum as I just bought a X3XRS. In reading thru the forums looking for setup and performance advice I noticed there's not a lot of attention being paid toward the most important part of getting your machine to really rip...clutching...so I decided to write what I've learned over the years to help you get a good setup.
I do not sell parts and have no financial interest in writing this, but I guarantee if you read, understand and apply the knowledge in this article you WILL beat your friends in a race with the exact same stock or modified sxs's as well as enjoy a more reliable ride.
There are several different ways to clutch the same machine and end up with the same result. A clutch kit or your buddy's setup on the same exact machine most likely WILL NOT be perfect for your machine, it may be close but not perfect. There are variances in each drivetrain and engine which affect clutching and make each unit it's own woman....you need to treat each one as an individual.
From my 20 years of experience drag racing snowmobiles- (same exact clutching setup as on your Can Am and most other sxs's) this is how you approach dialing in your clutching. You can enjoy routinely winning a race with identical stock machines just by properly setting up/machining your stock clutches. We run OEM clutches that we machined, aligned and tuned on 2 and 3 cyl 2 strokes as well as 2 and 3 cyl 4 stroke turbos and win against guys with billet clutches every weekend and only change belts two or 3 times a season for wear. It's all the in the setup.

Know this one thing- HEAT breaks belts 99% of the time. Period.
Finding out where the heat comes from, fixing that issue to drop belt temps AND THEN changing springs/helix/ramps as necessary to keep your shift rpm where the engine makes peak power/tq is your main goal.

First I'll explain the components and concerns with each then tell you how get them to work together properly.
BELTS- there's a couple main manufacturers out there that make all belts and for the most part unless you encounter an issue you cannot correct with the information here (or made your own motor mount that changes the clutch center to center distance), there's no need to run another belt manufacturers part- stick with the OEM because nobody does more R&D than them. (That being said watch when you get your new belts from this point forward that the manufacturer did not change the rubber compound to a harder or softer version than you run, they occasionally do that and it is usually indicated by a part number change). Moving to harder or softer belt compounds change the shift characteristics of your clutches.
The width of the belts is critical and for the most part will be dead on spec when they are new- we do not see much variance here. The belt width will wear with use and the shift characteristics will change with wear, you need to measure the belt clearance with a feeler gauge as follows- with your clutches and NEW belt installed and your clutch mud cover removed start the machine in neutral at idle for 10 or so seconds then shut it off. Make sure the side of the belt is touching one of the sheaves. Now use a feeler gauge to see how much clearance there is between the other side of the belt and sheave- this should be @.025" or so. Don't worry about the exact measurement at this point, just measure it and write it on the wall of your garage.
Belts DO vary in length (even 5 identical part number belts will be different). Make sure you put on the same belt manufacturer and length that you set your clutches up with and stick with that from now on. If you change the length more that 1/32" or so your clutching characteristics will change. To measure length of a belt- wrap a piece of white masking tape around the outside of the belt (follow the belt in a circle)(measurement will be like 26" not 3", follow?) and put a mark on both ends on top of each other where they overlap at the end. Now take that tape and lay it out on a flat surface, MEASURE THE DISTANCE BETWEEN THE 2 MARKS ACCURATELY AND WRITE IT ON YOUR GARAGE WALL WITH MARKER. Take that piece of tape to the dealer and have them lay out all the belts they have of that same part number on the table. Now wrap that piece of tape around each belt one at a time and you'll see what I mean. When you find a couple belts that match your length BUY THEM! If you don't find any that are within 1/32" just wait till their next batch comes in. Don't ever run a longer or shorter belt, if you don't have to, as your clutching characteristics will change.
When you get a new belt home the FIRST thing you will do, before it touches your clutches, is put it in the kitchen sink and scrub it real good with soap and warm water. The belts have mold release compound on them and if you run a new belt without washing it you will transfer the compound onto the clutches and that will make the belt slip and stick causing heat and poor shifting.
PRIMARY CLUTCH- also known as the drive clutch. This has flyweights (aka ramps or weights) in it that, with increased rpm, push against the rollers with centrifugal force and move the moveable sheave toward the fixed sheave to increase the "pulley" diameter which changes your gear ratio as your vehicle accelerates. I call this "shifting out".
The weights come in different gram sizes. Always change them in sets of 3 or 5 respectively for a 3 or 5 weight clutch or sets of 2 (180 degrees apart) on a 4 or 6 weight clutch. The more the weight weighs the faster the clutch will shift out and try to accelerate the vehicle. At the same time your trying to accelerate quicker with your new heavier weights you are asking more from your motor. If you have the HP then the rpm will only drop slightly or not at all and you will accelerate quicker. If you don't have the HP your rpm's will go down and you'll go slower. The object is to slowly add weight and test. If it keeps accelerating quicker then keep adding weight till it slows down and go back to your quickest setup. If your rpm curve is straight and too low (your at 7500 and want to be at 7800) then you put the next lighter set of weights in. This should shift slower and allow your motor to rev a bit more.
The Resistance to shifting out is provided by the primary clutch spring. The spring has a rate which is expressed at 2 different points. Initial and full shift. Adding a spring with more pressure has the same effect as putting in lighter weights. It's a balancing act as they work together. You shouldn't need to change your spring unless it goes bad (and they do after a couple years, the pressure they exert typically fades). OR you want to change the shift rpm curve because it can't be done with tuning the secondary in the next paragraph. Once we have our clutching working properly at initial setup we NEVER change primary springs other than for them wearing out. Then we replace it with the exact same spring part number from the SAME MANUFACTURER.
SECONDARY CLUTCH- also known as the driven clutch has a spring and a helix (aka ramp). The secondary clutch is pulled open during shift out by the primary clutch shortening the belt as it's "pulley" diameter increases. The helix and spring resist shift out and also control rpm during the run. No need to touch the secondary spring usually unless you are slipping the belt in the secondary-but this is rare unless you have a very heavily modified motor or are drag racing with a ton of traction. The helix comes in different angles (like 50 degrees) even multi angles (like 50/40). Changing the angles of the helix is necessary only when you need to change the rpm curve (what the rpm does during a 1/4 mile full throttle run-(like starts at 7000 and slowly climbs to 8000). It's important to watch what the rpm does during the entire run so a data logger or a GoPro is handy. The more the angle then the less the secondary will resist the shift out and the faster you will accelerate. Same thing as adding weight to the primary clutch but You shouldn't really tune for acceleration here primarily but you should straighten your shift curve out here. Let's say you want your motor to run 7500 rpm the whole time during the run and you are seeing it start from 7000 just after you mash it and climbs to 8000 rpm. What I would do is take your 50 degree straight angle helix (I'm guessing at what you have for demonstration purposes) and put in a 48/52 multi angle helix. By lowering the first angle you will allow the rpm on the first part of your run to come up. By increasing the second angle you are lowering the rpm at the end of your run. If your result is not as dramatic as you want then I would try a 46/54 and see if it's better. Lots of trial and error and note taking. Best not to deviate too far away from stock helix angles to an excessively high helix angle in an attempt to control rpm. I would add more primary weight to get your rpm's down first (just trust me). An excessively high helix angle could bring you down a rabbit hole of issues which even the best tuners have to bail out of.
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ALWAYS get replacement or different springs/helix/weights from the same manufacturer that you initially used as there's BIG variance between published rates/angles and what they really are. You won't know what your getting and all your tuning is thrown out the window. We use Dalton out of Nova Scotia exclusively as their parts are DEAD ON accurate. Not saying that's who you should buy from but that's who's products we're happiest with.
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Now that you understand what your looking at we'll go to the next step.
INITIAL CLUTCH SETUP- you MUST check the following BEFORE you even think about tuning or changing helix/Ramps/springs etc. or changing belt manufacturers due to blown belts. If you can remove the clutches and entire clutch guard then reinstall the clutches that would help you out in the following steps. It's not necessary to do but it's definitely more difficult with it on.
Check your clutches are parallel to each other by removing the belt and putting a straight edge on the back side of the secondary or primary on a machined part of the clutch and check that the other clutch is parallel to it. (It will be offset but should still be perfectly parallel).
Check your belt deflection. This is the amount you can push down on the center of the belt between the 2 clutches. If it's too much your slower speed shifting will suck. If it's too tight you'll get poor clutch component life. There's a spec in the CanAm service book for this. You can adjust it by shimming inside the secondary clutch. If you bring the sheaves closer together it will get tighter, shim the sheaves farther apart and it will get looser. We have on occasion needed to machine the base of the secondary sheaves off to allow the sheaves to get closer together.
Remember what I said about heat earlier- Any primary/secondary clutch misalignment at initial all the way thru full shift will create heat- eat hp like crazy and destroy belts. We almost always find misalignment from the factory- you need to full shift out the clutches installed and check that. What I'm talking about is when the clutches shift out the belt moves over as it climbs up the sheave. If the secondary doesn't move with the belt then you will end up with a belt that's running crooked in the pulleys and that will create heat. To check this you start the vehicle in neutral and let it idle for 10 or so seconds.(the object is to get the clutches and belt to their happy place) shut the vehicle off and get a straight piece of metal (you will probably have to custom make a piece that fits by cutting to length, just make sure it's straight). Remove your clutch bolt and put a long threaded rod in the clutch (just google what thread your clutch puller is to find out what diameter and pitch of threaded rod you need. You'll need a 8" long plastic or aluminum tube big enough to fit over the primary clutch center shaft and a washer and nut for your threaded rod to push on the sleeve. Make sure your the stuff you use to do this is good quality and strong as you will be compressing a 300+ pound spring. (I attached a picture of one I made out of high strength plastic). Put your custom straight edge on the back of the primary clutch machined surface and don't touch the secondary clutch at all. If you move the secondary you'll have to start over. Now see how the belt lines up with your straight edge. It should be perfectly parallel. If not you will need to shim the complete secondary clutch on its shaft as necessary to align it. Remove the straight edge for now.
Once that's complete then start tightening the nut on the primary compression tool you made AS you turn the engine and clutches by hand in the normal direction of rotation. The object is not to crush the belt but to continually turn the clutches as you tighten so the belt starts riding up the sheave. Keep doing this until your primary clutch is fully shifted out (this is when the 2 sheaves touch at the base and you notice the nut gets hard to turn). If you think the secondary clutch has stopped shifting like it's stretching the belt before you can full shift out the primary- THATS BAD- and you need to find out where it's binding (usually metal to metal contact somewhere) and correct that before you continue. Now do not touch the secondary clutch, Turn the primary clutch 20 or so revolutions to get the secondary and belt to their happy place. Measure the belt alignment with your straight edge exactly as I told you before. It should be perfectly parallel, if it's not then you will need to allow the secondary to float on its shaft by removing shims in the direction it needs to go until it's perfectly aligned. Usually we float our secondary's @ .250" or so depending on the measurements we get. The shaft that the secondary mounts too will require a slight amount of grease on it so the clutch can self align during operation.
Machining on factory clutches is almost always crappy so while you have your clutches fully shifted out check a couple other things.
1. See if the bottom of the belt is hitting the secondary clutch center. It SHOULD NEVER hit the center (this can be very difficult to see and may require a mirror and a flashlight) there's almost always some space here and if it's hitting you gotta fix that before continuing.
2. See if the top of the belt is even with the top of the primary. If not AND there is space between the bottom of the belt and the secondary as checked in #1, then we usually disassemble the primary and machine the base of the primary clutch sheaves off a bit to allow them to shift out more. You need to do a little bit then recheck #1 and #2 until your either getting close to touching the secondary center or the top of your belt is even with the top of the primary. Also don't take a ton of material off the base of the primary sheave as your loosing belt contact area when you machine material away.
As Airdam mentioned in another post the clutch sheaves were warped on some clutches causing issues so get that runout checked and have them replaced by your dealer or machined to true them up.

Any belt slip from too much hp and not enough sheave side pressure (due to light weights, high helix angles or weak secondary springs) does the same thing- (if either clutch is grooved or has rubber on it that's your sign)

KEEP THE CLUTCHES CLEAN!!!- and I mean real clean.

Now it's time to tune to the HP you have- yessssss!

There's the proper way which saves a ton of time-(and money in the long run-trust me on that) -get your motor tuned on a MOTOR dyno (not a chassis dyno) (or have your performance mod company supply you with their r&d motor dyno sheet from a unit they've proven which is identical to yours) and take home a dyno sheet so you KNOW where your motor makes power and subsequently can clutch it to keep it at that rpm. Then either change clutching parts as you think and test it in your back yard until you get it to shift right or THEN take it to a chassis dyno to do your clutching there.

If your field testing- DONT GO BY SEAT OF THE PANTS FEEL AS WE'VE PROVEN THAT IS EXTREMELY INACCURATE. Use a Stalker ATS radar gun connected to a laptop to plot out acceleration curves.

The other way is just to guess at what RPM your motor makes Power by extensive trial and error. This is a nightmare and I won't help anybody with this.

Below is from someone else.


Good luck. The amount of "slip" or lack of belt grip is contrilled by the secondary clutch spring. It is a must to change out the stock secondary spring if you make adjustments to the primary clutch if you want your belts to live. Particularly if you are looking for a higher rpm engagement or shift out. For those with ecu flash or bullydog type tunes with extended rev limit, I find it much better to add shims and limit primary clutch travel. This keeps the overall gearing lower on top end. Much better for big hills and much easier on belts. How much additional shims you add depends on how many top speed mph you are willing to give up. For me, I never need to go over 65mph so I add shims on the primary mainshaft behind pressure plate until my rev limit hits at about 65-67 mph. Your car will love you. Believe me.
 

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That's funny,I posted long time ago that if he did clutch work he would have too quit his real job.And maybe get overwhelmed.Hope he's doing well.
 
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