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Pre war Burman clutch

methamon

Well Known and Active Website User
Non-VOC Member
Pre war Burman clutch

My Burman clutch will not operate satisfactorily in as much as first gear engagement from a standing start is dreadful., that is to say it produces a horrible grating noise before engagement I have checked all the things which I think are obvious including:

There is approx 1/8” lift on the clutch push rod
Cable. pivots & push rod are lubricated
Plates lift squarely
There are no burrs or indentations either on the ears of the plates or the basket
I replaced the original perforated plate / cork insert arrangement.
I changed the oil from 20/50 to 10/30

When in gear with engine stopped the clutch can be pulled in and the bike pushed forward, i.e. the clutch appears to work ok.
I am aware that if left standing the clutch will stick and needs to be freed up.
I am also used to paddling bikes forward and engaging gear to prevent grating.

The problem is that this clutch appears to defy logic and I really do have to sort it one way or another as the grating is just shocking. I am aware that Conways do a Japanese clutch as a kit but surely these clutches used to work?
Can anyone provide any informed comment leading to a solution?
 

Hugo Myatt

Well Known and Active Website User
VOC Member
Burman clutch

I have a similar problem with the post war Comet/Burman clutch.I have two Comets, one solo and one with a sidecar. Both are in good condition regarding lift mechanisms, splines and plates etc. Both stick over night but both free off fairly easily in the morning. The solo has no problems at all after that but the outfit clutch gets worse as the ride progresses. It starts to drag when changing gear especially changing up, which on the outfit can cause unscheduled changes of direction. The only difference between the clutches is the material on the friction plates. The solo has an ancient friction material that looks like an amalgam of stuff tightly compressed together whereas the outfit clutch is a completely smooth material. It is this material that seems to stick to the steel plates. I have run it on straight 30 weight, 10/40 weight and ATF but nothing makes any difference. When I strip the clutch and clean plates in petrol it works perfectly for about two weeks but then gradually the dragging re-appears. I am beginning to suspect that modern friction materials do not work in wet clutches whatever may be claimed for them. Perhaps we ought to go back to cork!
 

Vic Youel

Well Known and Active Website User
Non-VOC Member
Burman Clutch Sticky

My Comet had the same problem. It is currently dismantled and awaiting a Conway Honda replacement.

The two new plates do not seem to stick but the old ones (asbestos and wire mixture) were really stuck....even with transmission fluid in the chain case.

Jeff, you are welcome to swap some of your plates with my newer ones but is the clutch basket up to the job...... with the amount of engagement of the clutch basket splines to the main shaft of some 1/4 inch it will surely shear just like mine. Too much of the spline length is taken up with the clumsy bearing roller arrangement. What an awful design.

Hopefully the Honda one will prove much stronger.

Cheers

Vic
 

Hugo Myatt

Well Known and Active Website User
VOC Member
My Comet had the same problem. It is currently dismantled and awaiting a Conway Honda replacement.

The two new plates do not seem to stick but the old ones (asbestos and wire mixture) were really stuck....even with transmission fluid in the chain case.

Jeff, you are welcome to swap some of your plates with my newer ones but is the clutch basket up to the job...... with the amount of engagement of the clutch basket splines to the main shaft of some 1/4 inch it will surely shear just like mine. Too much of the spline length is taken up with the clumsy bearing roller arrangement. What an awful design.

Hopefully the Honda one will prove much stronger.

Cheers

Vic

I, too am considering a Conways clutch conversion. However with due respect to Colin Jenner I would like to get some feedback from other users before I take the plunge. Over the years there have been many multiplate conversions for the twin clutch and each has been lauded as the best thing since sliced bread. Only later on does one hear of the endless problems that have emerged with them. I need a fit and forget clutch on my Comet that does not drag or slip and works happily in oil. So please let's hear from all you users of the Conways conversion.
 

Comet Rider

Well Known and Active Website User
VOC Member
Conways clutches

Hi Hugo,

Both dad and I run the Conways Honda clutch on our Comets (dads 600 outfit and my 580 solo)

Whilst I seem to have no problem (I do have a complicated starting ritual) dad does have the occaisional graunch when going into 1st gear from cold, but is then OK.

My starting ritual involves pulling in the clutch lever, then kicking the bike over quickly 7 or 8 times to ensure a free clutch, we both run Honda clutch levers which give a greater lift at a higher lift ratio. Also we are both running Mobil 0W40 oil in the primary.

Hope this helps

Neil
 

Albervin

Well Known and Active Website User
VOC Member
Pre war Burman clutch

My Burman clutch will not operate satisfactorily in as much as first gear engagement from a standing start is dreadful., that is to say it produces a horrible grating noise before engagement I have checked all the things which I think are obvious including:

There is approx 1/8” lift on the clutch push rod
Cable. pivots & push rod are lubricated
Plates lift squarely
There are no burrs or indentations either on the ears of the plates or the basket
I replaced the original perforated plate / cork insert arrangement.
I changed the oil from 20/50 to 10/30

When in gear with engine stopped the clutch can be pulled in and the bike pushed forward, i.e. the clutch appears to work ok.
I am aware that if left standing the clutch will stick and needs to be freed up.
I am also used to paddling bikes forward and engaging gear to prevent grating.

The problem is that this clutch appears to defy logic and I really do have to sort it one way or another as the grating is just shocking. I am aware that Conways do a Japanese clutch as a kit but surely these clutches used to work?
Can anyone provide any informed comment leading to a solution?
My 1938 Comet has a sticky clutch due to vintage corks & my inability to find a straight replacement for them here in Australia. For the time being I can get by if I do the following: before starting I pull in the clutch lever & depress the kick start until the plates release then start the bike. If a loud noise emits from gearbox when trying to select 1st I just hold the clutch in & blip the throttle a couple of times, this usually frees the clutch. On the move I usually have no problems but again if there is a reluctance to engage the gear I blip the throttle to free the clutch. What replacement plates did you use? Have you tried selecting 2nd then come back to 1st? I assume you are talking about oil for the primary drive when you say you use 10/30, is it synthetic?
I am determined to not replace the clutch with a Honda part unless it really becomes impossible to replace the clutch plates as that seems to be using a shotgun when a pea shooter is required...... haven't seen a pea shooter for years ;)
 

methamon

Well Known and Active Website User
Non-VOC Member
What replacement plates did you use? Have you tried selecting 2nd then come back to 1st? I assume you are talking about oil for the primary drive when you say you use 10/30, is it synthetic?

I am unsure what the spec was for the replacement friction plates other than the material is bonded. I did wonder about 2nd then into first but haven't tried it yet. Yes, on Sunday I drained the 20/50 from the primary & replaced with 10/30 which was synthetic.

I think the problem must be either that the driving & driven plates stick together in groups or a bunch when the pressure plate is lifted or if the springs are preloaded too much they might become coil bound on lift.

The handlebar lever is 1" c/c between pivot & nipple and I reckon this translates to adequate lift at the pressure plate
 

Hugo Myatt

Well Known and Active Website User
VOC Member
Conway clutch

Hi Neil,

Thanks for our input. It seems this clutch sticking problem is not a new phenomenon. My copy of 'Hints and Tips for Motor Cyclists' 13th edition published some time in the 1930s says in hint No. 120 regarding sticking clutches - 'Another good scheme is to use a mixture of paraffin and engine oil in the chaincase instead of plain engine oil. Half-and half is quite satisfactory and, as a rule, will be found materially to reduce the gumming tendency.' I wonder what that would do for the drive side main bearing?

Hugo
 

vincenttwin

Well Known and Active Website User
VOC Member
Conway Clutch

I am running a Conway Honda Clutch in my pre war A comet ,and it is great never sticks ,very little grinding , if it does its my fault for having the throttle to far open ,
over all its great.
Peter
 

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