Author Topic: Clutch "grabs" too quickly  (Read 1690 times)

Offline Felters

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Clutch "grabs" too quickly
« on: 28.09. 2011 06:13 »
Well you fix one thing and another issue leaps out...

The clutch has always been a bit "grabby" but now the engine is running smoothly it's become more obvious. I guess it may actually be getting worse. There's no clutch slip under power but getting a smooth engagement from a standing start is nigh on impossible and there is a distinct clunk as you release it.

Once underway it seems fine but kangarooing my way through traffic jams is not something I do for fun!

Where do I start?

Mike

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Offline Flatboy 1950

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Re: Clutch "grabs" too quickly
« Reply #1 on: 28.09. 2011 07:55 »
I suspect the clunk may have something to do the face cam /shock absorbing mechanism that is part of the crankshaft sprocket & would check here first.

Cheers , Flatboy.
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Offline chaterlea25

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Re: Clutch "grabs" too quickly
« Reply #2 on: 28.09. 2011 15:29 »
Hi Felters,
Which clutch does your bike have?
There are some pattern plates out there that give this problem!!!
The friction material is a light greyish green colour on those plates

HTh
John O R
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Offline Felters

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Re: Clutch "grabs" too quickly
« Reply #3 on: 28.09. 2011 16:34 »
I need to get the primary cover off and see what lurks beneath. I've only had the bike a few weeks so have no idea what plates it has or how they're adjusted.

What are "good" plates? Surflex?

Rgds
Mike
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Offline Goldy

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Re: Clutch "grabs" too quickly
« Reply #4 on: 28.09. 2011 19:35 »
Yes suflex are the good one,s. I would make sure that the clutch centre nut is not loose.
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Offline Felters

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Re: 1959 A7 Clutch "grabs" too quickly
« Reply #5 on: 02.10. 2011 02:56 »
So started to have a look last night - haven't got the clutch plates out yet (where can I get the "special tool" that engages with the four nuts that hold the pressure plate on?) but it looks to me like the nut on the cush drive shock absorber is has started to undo itself and has gouged some fairly deep grooves to the inside of the primary chaincase cover.

There are also some marks in the dome covering the clutch...

The special nut that SRM do for the cush drive (http://www.srmclassicbikes.com/download-catalogues) on page 47 seems to be the answer to my simple way of thinking. Any other advice gladly received...





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Offline t20racerman

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Re: 1959 A7 Clutch "grabs" too quickly
« Reply #6 on: 03.10. 2011 18:17 »
So started to have a look last night - haven't got the clutch plates out yet (where can I get the "special tool" that engages with the four nuts that hold the pressure plate on?) but it looks to me like the nut on the cush drive shock absorber is has started to undo itself and has gouged some fairly deep grooves to the inside of the primary chaincase cover.

Pretty standard that! Generally the washer is left off behind the big nut thing and it unscrews itself. The SRM thing is good, but the std one is fine if fitted tightly with washer.

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Offline Felters

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Re: Clutch "grabs" too quickly
« Reply #7 on: 04.10. 2011 20:45 »
Picked up a cush nut from SRM yesterday - a 500 mile round trip but the weather was nice and the RT needed an outing.

It was only £1 more than the standard item... we will see how it goes.

Rgds
M

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Offline Felters

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Re: Clutch "grabs" too quickly
« Reply #8 on: 07.10. 2011 13:27 »
Reallllllyyyyy struggling to get the old mangled cush nut off - any top tips?

M.
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Offline A10Boy

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Re: Clutch "grabs" too quickly
« Reply #9 on: 07.10. 2011 17:48 »
Two pairs of Stilsons, one on the "nut" one on the sprocket. Failing that dont be afraid to give it some welly with a big hammer and cold chisel.

Things to check.

1/ The splines on the crank
2/ The cush is working and tightened
3/ The chain isnt too loose [1/2 in to 3/4 up and down]
4/ The clutch centre / nut is tight on the shaft
5/ The clutch basket isnt too worn or the tangs on the plates will stick
6/ The pressure plate lifts evenly
7/ The plates are clean and aren't gummed up with gummy shite
8/ The gearbox to engine plate bolts are tight and the box isn't moving
9/ That you have plenty of patience
10/ That when its all back together the oil is at the right level.

If I can think of more I will let you know.

Good luck
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Andy

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Online bsa-bill

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Re: Clutch "grabs" too quickly
« Reply #10 on: 07.10. 2011 18:26 »
heat it - heat gun is good and safer than a naked flame
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All the best - Bill
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Offline Felters

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Re: Clutch "grabs" too quickly
« Reply #11 on: 10.10. 2011 13:19 »
this...

4/ The clutch centre / nut is tight one the shaft]

Funnily enough if I'd read the f&*$£?g Haynes manual - it gives a loose centre nut as a cause for the clutch grabbing. 

Doh!

Thanks all

Mike
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Offline A10Boy

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Re: Clutch "grabs" too quickly
« Reply #12 on: 10.10. 2011 15:09 »
Dont believe everything you read in that particular publication...
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Andy

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Offline iansoady

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Re: Clutch "grabs" too quickly
« Reply #13 on: 11.10. 2011 11:50 »
Dont believe anything you read in that particular publication...

Corrected for you.....
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Ian.
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Offline Felters

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Re: Clutch "grabs" too quickly
« Reply #14 on: 14.10. 2011 06:42 »
unlikely as it seems - on this one occasion Haynes were actually correct.

OK so it's still not exactly silky smooth but tightening the centre nut to the approved torque setting (two shoves and a grunt) has made a real difference.

I do like the bike - but I find the lack of detail on some of this stuff hilarious. Did BSA not have torque wrenches? Although I suppose their customers of the time probably wouldn't have had them anyway. I'm coming around to thinking that a lot of this stuff is variable and really doesn't matter that much  *smile*

Mike
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