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bgeacook

using Japanese bike clutch plates

14 posts in this topic

I'm interested in using friction material plates but NOT the more expensive Barnett ones for bultaco.  read on here about using certain Japanese bike plates and it looks like the kit that is sold by Bultaco UK(?) uses that type plate evidenced by much bigger inside dia.  Anyway, all these plates are listed as 110 O.D.  but I'm measuring the Bultaco hub I.D. right at 110.  are the plates slightly under or do they have to be filed down to fit?  I know the tabs are wider but I'm talking about the diameter of the plate fitting the dia of the hub.

unfortunately I just buttoned up the clutch side on my son's 87 Honda cr80 after inspecting the clutch.  at the time I wasn't aware of the interchange-ability of the Japanese clutches.  I'm not too interested in dissembling his bike again just to check the fit of the Honda plates.  thanks

 

Screenshot_2017-02-14-06-57-47.png

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its there in black and white for you to read?

Whatever you do it will still be a bultaco clutch and it isnt going to make much difference.

Ride it.

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got the plates (kx80/85), fit them, rode it.  pleased.  that's the short version.  

long version- 1)  is a little tricky getting the tabs filed equally so plates fit.  the overall dia is just under the advertised size of 110mm but not by much so tabs have to be just right.

2) the stack of plates comes out to about .008" less than the stock so I was not concerned about using them with the pin-type center hub.  the threaded type would be easier but I couldn't justify the cost to buy one.

3) I used only three springs.  I believe they are heavy duty ones.  possibly Barnett- dad couldn't remember, it's been years since he changed them.  and apparently he lost one as there was one that was a little shorter and plain gray, not black, like the other 5.  assuming that one is stock.

4) the pressure plate does move out slightly unevenly, which could be addressed easily with a threaded hub.  I think the problem is the spring cups, being stamped, are not equal depth.  out of the six I'm sure three the same size could be found.

5) no slippage, kicking it over or shifting into high gears.  hot or cold it kicks over fine and I rode it down the street, shifting up, lots of throttle, and no slipping.

6) engagement is nice and smooth, not grabby at all

7) clutch pull is much easier than before, not modern bike easy, but still a big improvement.

8) paid under $20 USD for the plates!

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Clutch is easier because there are less springs, it doesnt slip under reasnoble load in 5th/6th?

Pressure plate should pull out straight, if this is achieved lever action should be lighter, altough not sure you'd get that with 3 springs.

Well done for doing it though food for thought......

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ordered a set to try,£10!!!!

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OK, to file the tabs properly you need a simple fixture like this one. It's made from 12 x 32 flat and will make the tabs a consistent width. Note how the small piece on the underside is only welded to one side; this allows the tool to be squeezed together when you hold it in the vise, holding the clutch plate in position. The lower edge of the tab rests on the large cross-piece, the small cross-piece supports the opposing tab and locates the plate laterally so you don't have to position the plate manually. You just drop the plate in, squeeze it in the vise and start filing. The vertical piece on the top is just a guide or fence to prevent you from filing a notch into the OD of the plate. It takes about five minutes to file a plate but usually you also have to dress a few high spots off the OD so the plate slips in easily. I've done quite a few sets like this, mainly used with thin 1.2mm steel plates that I get laser-cut locally. The thin steels let you use more plates which helps with high-output engines.

 

My apologies for the terrible phone photos - hope you can see what I mean.

 

clutchtool1.jpg

clutchtool3.jpg

Edited by oldjohn
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On 18/02/2017 at 4:58 PM, nigel dabster said:

Whatever you do it will still be a bultaco clutch and it isnt going to make much difference.

Ride it.

Nothing could be further from the truth - you can easily double the torque holding capacity of a Bultaco clutch with the right parts and oil (hint: don't use ATF).

The clutch cover with the welded attachment is part of a testing fixture I made to test different plate combinations and oils. Some would hold well over 500lb/ft of torque. The reason for all this clutch work is the 75hp LSR bike that's shown semi-finished below. That engine has destroyed a set of Barnetts in less than an hour, while the Honda plates with thin steels and an appropriate oil hold up much longer. Of course you don't need all this capacity with a Sherpa, but a better clutch allows the use of lower spring pressure without slipping, and that makes the bike more pleasant to ride. 

bulpipe.jpg

clutchtool2.jpg

Edited by oldjohn
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sorry, what i shouldve said is set up your trials clutch so that it works well enough as to get anything any better involves a fair bit of workshop time. Anything you want to do can be done with engineering but youd better spending this time riding a trials bike.

Having saig that ive got the kx plates ready for install.

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On Friday, March 10, 2017 at 11:24 AM, oldjohn said:

Nothing could be further from the truth - you can easily double the torque holding capacity of a Bultaco clutch with the right parts and oil (hint: don't use ATF).

What oil would you recommend?

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6 hours ago, model80 said:

What oil would you recommend?

Oils specifically designed for motorcycle engine/clutch/gearbox use were the best. Castrol Power 1 Racing 4T for example had around 15% more torque capacity than any of the ATFs - not a massive improvement I know but it all helps and might be the difference between a clutch that slips and one that doesn't. The same oil can be used in the gearbox.

Edited by oldjohn
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On 12/3/2017 at 7:41 PM, oldjohn said:

Oils specifically designed for motorcycle engine/clutch/gearbox use were the best. Castrol Power 1 Racing 4T

Many thanks oldjohn, I checked out the Castrol website http://www.castrol.com/en_gb/united-kingdom/products/motorcycle-and-scooter/engine-oil/power1-brand/power1.html and they list several types of your recommended oil. Of the various types 10w/30, 10w/40, or 15w/50 etc, which would go for?

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The only one I tested was 5w 40. Other grades may work just as well but I liked that this one had little drag when cold yet still had more holding power than ATF.

Edited by oldjohn
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I use Castrol Power RS 5W40, which works great in my 350 Sherpa with a modern type clutch (from InMotion). No drag, smooth action and no slippage in higher gears.

When I've run out of that oil, I'll be testing Castrol Power-1 10W30.

I would go for the 10W... instead of the 15W... because it's viscosity in colder temperatures, is closer to the 5W... oil

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10 hours ago, guys said:

I use Castrol Power RS 5W40, which works great in my 350 Sherpa with a modern type clutch (from InMotion). No drag, smooth action and no slippage in higher gears.

When I've run out of that oil, I'll be testing Castrol Power-1 10W30.

I would go for the 10W... instead of the 15W... because it's viscosity in colder temperatures, is closer to the 5W... oil

If the clutch isn't slipping or dragging with the oil you're using now then realistically there's nothing to gain by changing to something else. I only tested maybe a dozen different oils so it's quite likely that there are others that are as good or better than the Castrol Power 1. Having said that, all the non-friction-modified oils had very similar torque capacities so probably the best approach - as you said - is to pick one that doesn't get too thick when it's cold or too thin when hot.

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