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dan williams

The Beta Clutch Fix

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Sorry Dan for being a bit thick I have an 08 Rev 3 4t and it has the original kill switch, the rear light works but the section from the headlight bulb to the wiring harness is missing off the front light, would i benefit from adding an additional earth and if so where do i run the earth from. Any advice would be appreciated, hopefully carrying out the clutch mod next week time permitting (bloody weather causing issues in work)

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Hmmm I don't know squat about the 4T wiring but you can never have too much ground so...

On my 2T the whole switch cluster, lighting system, kill switch ground came through a lug bolted behind the headlight to the top triple clamp. Stupid idea since the surface treatment of the triple clamp makes it an insulator. I reasoned out that if that connection wasn't secure (and it wasn't) that the kill switch had to find ground through the lights. Unfortunately that meant the lights were "hot" through the kill switch. Bad situation. I took the big black wire that attached to the lug and ran it back down through the harness out at the bottom of the spaghetti tubing under the little plastic fuel filler cover and reattached the lug with solder and bolted it to the 10mm bolt on the frame tab that the regulator mounts to with a daub of silver paste (lithium grease and silver particles) used on CPU coolers. I also ran a second ground wire from that bolt to one of the ground connections of the ignition coil but that's probably overkill.

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"did" my clutch earlier this week. :o(just wanted to see the banana...)

It feels a bit 'strange' now, but also seems a lot more 'controlable'. Let's see what the difference will be, this weekend...

thanks Dan!!!

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I've just started on my clutch this morning, the plates were really stuck together when removing them! I've done one plate/disk so far but before I carry on, can anyone tell me what the thickness of the fibre should be, or the minimum height left? I measured both sides together and they measured 2.75mm on every plate/disk.

Thanks

Steve

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Ok Now i've done it. The modification. To the Rev4 250 4T. Before i started the clutch on the 4T was a significantly lighter pull then on the 2T i had. I have done the mods and cleaned up the plates, and take out two clutch springs. All the work was done with a needle file - no power tools - and it took 2.5hrs.

I never used to get much clutch drag but perhaps there is a little less drag when the bike is idleing. It is, perhaps, a little easier to find N but there isn't much in it. Now for the BIG change - i have a much more progressive clutch take up. Much better. Like wow! I have given't the bike some stick and no clutch slip yet. Will post back if i get slip... and will refit the two removed springs. :ph34r:

Ralph

Edited by NZRalphy

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Ok Now i've done it. The modification. To the Rev4 250 4T. Before i started the clutch on the 4T was a significantly lighter pull then on the 2T i had. I have done the mods and cleaned up the plates, and take out two clutch springs. All the work was done with a needle file - no power tools - and it took 2.5hrs.

I never used to get much clutch drag but perhaps there is a little less drag when the bike is idleing. It is, perhaps, a little easier to find N but there isn't much in it. Now for the BIG change - i have a much more progressive clutch take up. Much better. Like wow! I have given't the bike some stick and no clutch slip yet. Will post back if i get slip... and will refit the two removed springs. :rolleyes:

Ralph

2.5 hrs !!!!! blimmin eck Ralphy, it took me 4 and i thought i was on fire. gona reduce my porridge and have a look at that veggimite. :lol: (hope ive not started an international incident) :wacko:

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2.5 hours!!! I take about 8. Then again I'm working under a microscope and am a bit of a twit.

but just think dan, thats 8 valuable hours spent on thinking up the next improvement for us mere spanner monkey,s :rolleyes:

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Hey Dan

I must commend you for your well written technical article.

While I agree with what you wrote and the changes made there is MUCH more going on in the clutch that the lay person

misses, and much more that can be done to smooth out the clutch and its pull, and releasing.

We should talk as it is nice to have conversation with another tech head such as your self.

If only I had the time, patience, and computer skills needed to post my thoughts.

Cheers Dan.

BillyT

Edited by BillyT

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Nice writeup, Dan. I'm no expert, but your theory about the glue blocking escape path for the oil makes sense to me. BTW, I wonder how many tabs of a friction plate are really in contact with the clutch basket. I figure it's probably only 3 tabs (or maybe it is only 2) since the friction plate is free-floating relative to clutch basket center center. But of course it isn't the same 3 tabs all the time, so as you go through clutch engage/disengage cycles, it randomly "picks" which 3 tabs are pressing against the basket. That's why over time all of the tabs get worn down. Anyway, if I'm right about this, then I don't see any benefit in trying to match tabs precisely to the basket fingers.

For those folks who prefer to keep all 6 springs but would like to reduce clutch lever effort without spending money on lighter springs I can offer this trick borrowed from www.thumpertalk.com. You can use a washer under the spring retainer (obviously you will need 6 identical washers). Effectively this lengthens the spring "tower", or to put it another way, it reduces spring preload. Washer O.D. obviously needs to be slightly smaller than spring I.D. And washer I.D. needs to be just barely big enough for spring bolt to go through. I've done this mod on my enduro bike, and with 1.5 mm thickness washers the difference in clutch effort was very noticeable. The only thing to watch out for is to make sure you have adequate clearance between spring bolts and the clutch cover.

This works because springs are position-sensitive. If you have a spring rated at 1.0 kg/mm then it takes 1 kg of force to compress that spring by 1 mm, assuming the spring was completely uncompressed to begin with. And it takes 1 additional kg of force for every 1 additional mm of displacement. In other words, it takes 3 kg of force to compress a spring from its free length by 3 mm. If you have a certain amount of preload on the spring, then the force required to overcome the preload is exactly the force it would have taken to compress that spring from its free length to its installed length (i.e. down to its preloaded condition). So if the clutch spring free length is 30 mm, but its installed length is 25 mm, then you have 5 mm of preload. If they are rated at 1 kg/mm and you have 6 of them, then the force required just to budge the clutch pressure plate is 30 kg. If you reduce preload to 4 mm (by using 1mm washers) then the force is only 24 kg.

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im gonna try this mod at the weekend cleaning out glue etc ive looked at how its done and im up for the chalenge ill get the files and go for it

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Hi Billy

I'd love to chat with you sometime although I'm pretty sure I'd be out of my league. I always thought if I could get within spitting distance of what you and Jon know I'd be happy. I haven't been on here too long recently as I'm trying to release a product at work and running into all kinds of foolishness. It's wearing me a bit.

Copemech

Yes sorry for not responding sooner for the same reason. That and I have to figure out what I did with my caliper. It's in the truck somewhere....I think.

Fastducs

Yeah there is a certain logic to the question of how many tabs actually make contact. I would think it gradually becomes more as the plates wear in. The more the better though as reducing the pressure on any particular plate/basket interface reduces its importance in affecting the sliding of the plates. One thing I do wonder about with fewer tabs contacting is warpage of the plates as they are torqued unevenly around the perimeter and whether that has an effect on the spontaneous take off phenomena some pros experience at full throttle pre-slingshot.

The spring preload vs removing springs vs lower spring rate debate rages on. Well OK not really raging but is open for discussion. Two things it affects, how much pressure is actually on the plate while the clutch is engaged and how much is required to hold the beastie in when it is disengaged. One looks like an offset the other a gain or I guess it just pushes the two data points around on an exponential curve. (sorry started rambling there) The experiments to determine the transfer function of pressure plate pressure vs friction are beyond what I have the time to do. Though I'd love to see the data if somebody does it. Earlier someone did do holding pressure experiments for spring removal and spacer loading. The results are on here somewhere.

Skippy

It should work for the Techno as the fiber plates are the same part number as the Rev3 if I remember correctly.

Edited by Dan Williams

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