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dan williams

The Beta Clutch Fix

342 posts in this topic

22 hours ago, guys said:

If you've ever ridden an older Twin Shock bike, clutches on modern bikes are no problem at all. :rolleyes:  :)

Well yeah compared to my Maico but my friends had 307 Fantics and that was easily the match for any hydraulic clutch I've ever used.

Hey Chris, nice to see you back. I was getting worried when I didn't see you post for a while. I hate to say it but after years of use and many compliments on the pegs you sent me I mashed one. Felt horrible about that.

One thing I was considering working on was a magnetic clutch assist. With springs their simplicity is their problem. No matter what you do to make the pull easier pull is still a linear function. Magnets are exponential (I think, I suck at math). The pull exerted is inverse the square of the distance or something like that. If you overlay the transfer function of a spring and a magnet it becomes obvious that if done correctly the force applied by the spring with the clutch in will be relatively unaffected by the magnet but when pulled in the magnet will assist the action of the lever reducing the effort needed to hold in the lever. I also considered replacing the springs with magnets in various configurations. Of course life intruded before I got far into that development but it might be fun to revisit.

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Thanks for be advice everyone. This is something I'll look at a little later, but I certainly want to soften the clutch lever to minimise hand fatigue. 

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Hi all (and Dan),

I need to update on my last post from last year...I previously posted that I'd done the fix and the results were good at the time, but after having not ridden my 2014 Evo 250 since last year, the clutch seems to be as bad as ever! It's dragging horribly again. I've been out practicing in the woods a few times this spring and the old clutch gremlins are back; dragging like mad at times (sporadically but more often than not) and pretty much impossible to find neutral. I can't understand why, it's just been sat in the garage. I could try changing the oil for fresh oil but surely this can't be the answer, after all; the glue between the friction pads on the plates can't have reappeared! I'm using Putoline light gear oil btw.

On another note: Part of what led me to the 'Beta clutch fix' initially was that my bike makes quite a loud and disconcerting high pitch whining noise once it's in gear (with clutch either in or out). This noise is only evident when in gear, when it's in neutral there is no whine at all. Has anyone got any idea what this whining noise could be?? It's driving me crazy, it's got to be something obvious. I presume that because it only occurs when it's in gear (with the clutch in effect...either engaged or disengaged) that it's got to be a clutch related issue. I feel that it's the friction plates themselves, I would really love to get to the bottom of this whining noise as I strongly suspect that it is contributing to the clutch drag issues! I think the whining is loudest when a gear is first selected and during take-up but it's there even when the clutch is fully out, albeit to a lesser extent.  Can anyone help?

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The clutch steel plates may have some light corrosion, if that's the cause it'll clear with use.

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Possible but I've run it for about 5 hours now and if anything the clutch drag is worsening.

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I think I'm just going to stick a new set of plates in!

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Posted (edited)

Ooooh the whining noise doesn't sound good. Usually indicates a missing or chipped gear tooth. Check your tranny drain bolt.

As for the clutch going to hell after sitting that is not something I've experianced after the fix. Once the excess glue is removed the time to cold flow becomes irrelevant.  Do you have the 4 thin 2 thick fiber configuration? Are you using any additives that might swell the fibers?  Do you have any bent plates? 

I think a disassemble and inspect is in order. Nothing in the fix should cause what you are describing. Something is definately in need of attention.

Edited by dan williams

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Just another thought. Chewy posted measurements of his basket and hub runout. I wonder if there is some eccentricity in your clutch assembly. Perhaps a bearing is bad? That could also cause a whine but only with the clutch out and the tranny input shaft driven.

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9 hours ago, dan williams said:

Ooooh the whining noise doesn't sound good. Usually indicates a missing or chipped gear tooth. Check your tranny drain bolt.

As for the clutch going to hell after sitting that is not something I've experianced after the fix. Once the excess glue is removed the time to cold flow becomes irrelevant.  Do you have the 4 thin 2 thick fiber configuration? Are you using any additives that might swell the fibers?  Do you have any bent plates? 

I think a disassemble and inspect is in order. Nothing in the fix should cause what you are describing. Something is definately in need of attention.

Oh no, I hope not!! I've never found any metal bits in the oil though. I'll take the clutch apart again and double check thicknesses and trueness, by bent plates do you mean the friction plates or the steel discs? It all seemed to be in order when I did the work though. The strange thing about the whining noise is that it hasn't got any worse, it's just always done it since I bought the bike and it doesn't affect performance in any way, that's why I was thinking it had to have something to do with the clutch dragging. Yes, mine has the 4 thin/2 thick configuration and no I'm not using any sort of additive at all. I've just reassembled the carb and run the bike paying particular attention to the whining noise (running great now btw :-)), the noise only starts when I start to release the clutch, right up to fully out and is proportional in volume/pitch to engine speed. It definitely seems to me like it's being caused by the friction between the plates as they are biting. Perhaps it's just normal on these Betas but I haven't had it before on other bikes. It certainly doesn't seem like a mechanical (metal on metal) noise.

On another note, when I started it up the clutch was behaving perfectly; no drag at all and easy to find neutral!! Maybe the dragging is related to gearbox temp as it seems to get worse when the bike's nice and warm.

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Betas whine, try listening to a few videos and see if they sound the same as yours.

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Betas do whine a bit. Dammit why can't you guys all live near me so I can see these things in person. 

That's what it sounds like when I whine.

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Just to update on my clutch woes: It's now running absolutely sweet as a nut! I've done a few hours on it too on separate occasions and it's absolutely bob on :-) To summarise, all I really did in the end was change the two thicker friction plates for new standard thickness ones. I checked the steel plates for trueness (they were perfectly flat) and reassembled. I filled up with putoline gear oil (the nano-trans I'd ordered hadn't arrived yet!) and it was great; almost perfect with just the smallest amount of drag at times, it really made a big difference. once the nan-trans oil arrived I changed the oil again to the new stuff and now it's simply perfect! It's a dream to ride. The clutch feels extremely responsive at high revs and quick release and very controllable at low revs and slow release. I very highly recommend this putoline nano trans, it's fantastic stuff! Oh, just to confirm I has also done the clutch fix previously which seemed to help a bit at the time but strangely didn't last. Obviously it's all been down to the two thicker friction plates...and this mega oil. Btw, I didn't bother doing the glue filing and tab filing on the two new plates.

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Thanks again Dan for your help and advice

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Excellent. I've never thought the thicker plates were anything more than a solution looking for a problem or at least a hail mary attempt to fix what is easily fixed with the fix.

Last sentence brought to you by the department of redundancy department.

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Having only recently embarked on my trials experience I have been so pleased to have found the great advice and support on this forum. I thought you might be interested to see my clutch mod based on some of the excellent examples in previous posts - the previous owner of my Rev 3 270 told me it had had its plates de-glued and de-burred and I was pleased to discover he has done a good job - the clutch has only dragged a little since I have owned it - although it is very hard to find neutral, so I might have a go at the basket finger edges again.

I have been getting lots of arm pump and struggle as the day wears on - I'm sure my technique is poor and I'm still gripping everything a bit too tightly! - However I did try removing two springs and found the clutch lighter. I don't like this solution though as it "feels" wrong to unevenly load the plates, but maybe that's just me! 

So... I have just made a set of spacers based on the Evo ones - I am lucky to have a lathe so it wasn't too tricky - I used countersunk stainless screws so the overall height of the assembly is the same but each spring has 3mm less preloading. I haven't used it in anger yet but first impressions are good and it seems lighter. 

I'll let you know if it slips in higher gears, but to be honest I rarely use them!

Thanks for all the inspiration!

Mark

de glued clutch plates.jpg

turning.jpg

new screws and spacers.jpg

new clutch screws.jpg

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