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Discussion Starter #1
I'm coming from two worlds of centrifugal clutches and neither seem to explain the Burgman system to me.

As a kid I had a mini-bike which had a simple spring retract centrifugal clutch with shoes and a housing. When I revved it up the spinning shoes would extend outwards and make contact with the circular housing they rotated in and away I went. That housing was attached to the drive sprocket of the engine. It was a simple and effective system.

My snowmobiles were CVT drives but there was no clutch with shoes to speak of. There was, recalling from memory, a pulley attached to the engine crank with two sheaves, one stationary and one sliding. When I revved it up the sliding sheave moved inward pinching the drive belt and transferring power to the driven pulley which itself was spring loaded and would vary the ration depending on the load applied to the drive belt.

How's the Burgman make use of a minibike style clutch if it has both the rpm dependent and load dependent pulleys?

Hmm, maybe I just figured this out. The clutch is a guaranteed method to have a "neutral" available. There's no way the bike will move unless the engine rpm is high enough to engage the drive pulley.
 

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The clutch for the Burgman is mounted on the output pulley for the CVT. Both pulleys of the CVT are always turning and the belt moving as long as the engine is running. The only thing that varies is the relative speed of the pulleys based on the ratio at a given point in time.

The front or primary drive pulley is the one that has the variator that determines the CVT ratio and it does that based on engine rpm. It's pulley is in two halves like you remember in the snowmobile except it does not open enough to alloy the belt to stop moving.

The rear pulley is the one that spins the clutch and causes it to engage and it does that based on it's rpm which is governed by the ratio the CVT is in. It also is spring loaded like you remember in the snowmobile to open and close depending on the width of the front pulley so that the belt is always tight.

So since the CVT is always engaged the only way to disengage the rear wheel is to disengage the clutch. That is why it is mounted on the secondary or driven pulley. When the clutch engages it locks the secondary pulley to the output shaft going to the rear wheel.
 

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The clutch on most smaller scooters is like your old minibike in that it is a drum design with shoes and a bell. The shoes expand out and make contact with the bell. Both designs work on the same basic principle of rpm forcing a mechanism to move and thus engaging drive.
 

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Discussion Starter #4
Thanks guys, especially Buffalo, great info.

Now I have a much better picture in my mind of how the drive-line works.

So the 5 shoe aftermarket clutch is just more surface area for a better lock-up? Does that mean the 3 plate design doesn't lock up 100% tight?
 

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Well I guess that is what the guys who sell the five shoe clutch might say. They do want to sell you one of their clutches afterall. I've never had any problem with the OEM clutch in mine locking up 100%.
For that matter I've never had any issues with the OEM clutch in mine at all.
 

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Thanks Buffalo. I was gonna try to explain it, but knew someone else like you would do a better job.

So far as the three v five shoe clutch, it's a k7+ issue. Suzuki bumped up the engine displacement a bit in 07 and probably the weight too. I think the three shoe just didn't engage as quickly, leading to glazing. Mine had it bad at just 5k. The dealer swapped it out for a five shoe k8 version, and it lasted almost 30k. Not glad, but still glazes, just not as much. I think the pads are thicker too.
 

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I bet there is less stress on the 5 shoe clutch as opposed to the 3 shoe. The 2001-2005 Yamaha Zuma 50cc uses a 2 shoe clutch but they are notorious for failures especially with a 70cc kit{physically breaking!}. When Yamaha brought the Zuma back in 2008 they fitted a 3 shoe clutch that was a little bigger{OEM copy of what all the aftermarket clutches had gone to}. A lot of the guys with the earlier ones would fit the later 3 shoe clutch because it could take the extra abuse a 70cc kit put on the clutch{OEM is actually cheaper than aftermarket, at least good aftermarket}.
 
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