[phutton]

You don't need three arms to adjust the clutch stops, just two arms and a piece of string to hold the clutch in (out?). A rubber band cut for an inner tube also works.

A lovely piece of work - should go in Beaming for a wider audience.

P.

[m90]

Andy and Ian
Thanks for posting on this topic - I have limited technical skills but with your help I succeeded in adjusting the clutch of my 1925 Model 6. I was getting frustrated being unable to work out what was needed and your posts provided the set of instructions which I needed
Nick Shelley

[iansoady]

Just one minor point Andy.

"Rotate the clutch (with the back wheel in top gear) with the clutch raised and swing the kickstart pedal. The depth gauge will show any adjustment required to achieve a parallel rotation."

You don't need to use the kickstart - the back wheel will turn the clutch (and what's more you can do it from the left hand side so you can see what you're doing!)

[Andy Cubin]

Gents,

I have amended the definitive guide to clutch adjustment and been in the garage AND it works!

Here it is:

SUNBEAM CLUTCH ADJUSTMENT

1.   Clutch bridge
The clutch adjusting screw with lock nut is in the centre of the clutch bridge.  This screw holds the ratchet (clutch-operating) lever up against the push rod. 

This rod pushed the outer plate on the opposite side of the box, releasing the pressure on the clutch plates, thereby disengaging the clutch.

This screw must be adjusted so that the ratchet lever is just free without excessive looseness.

Firstly, detach the shackle that attaches the clutch cable to this lever.

Next, adjust clutch-adjusting screw until the operating lever that hangs down has appreciable slack in it.

Make sure the cable is not operating the clutch (which it wont be because it has been disconnected) then adjust the screw.

Ease the locking nut and adjust the centre screw in or out as required so it just touches the dome on the end of the rod -  you can feel this quite easily as you turn the screw as it will start to move the clutch. You can also see the dome moving by looking down at the top of the clutch bridge as you adjust. At this point just back off slightly - about a 1/4 of a turn..

The adjustment is correct when the operating lever has 1/8" play with the cable detached.

Once the adjustment is correct, tighten the lock nut.


2.   Clutch Cable
Once the operating lever has been correctly adjusted, The operating cable can be re-attached.  Excessive slack in the operating cable can be taken up on the small adjuster screwed into the front of the gearbox bridge leaving a small amount of play on the handlebar lever, when the clutch is engaged.

Because the bike has clutch stops on the primary chain case, the clutch cable must not be adjusted too tightly, otherwise the clutch pack and cover would come up against the stops before the plates have separated during gear change.

3.   Spring Nut adjustment.
If there is insufficient tension on the plates, it will be necessary to increase the spring pressure.  This can be done by removing the aluminium clutch dome to give access to the spring nuts.

If the spring nuts are over-tightened,  this will cause the clutch to be very stiff to operate.

In many cases even pressure is achieved when the spring nuts look differently adjusted as the springs will have worn / lost their temper to different degrees. A simple depth gauge or marked wire can show if the pressure plate if parallel. Rotate the clutch (with the back wheel in top gear) with the clutch raised and swing the kickstart pedal. The depth gauge will show any adjustment required to achieve a parallel rotation.

4.   Clutch Stop Adjustment.
Screw both stops out till well clear of the clutch plate when raised.

Put the gearbox in top, hold the clutch lever right in, and screw one of the stops in until you can feel some drag through the back wheel when rotating it. This means the stop is contacting the pressure plate. It also requires 3 arms.

Unscrew this stop a full turn and repeat the process with the other stop.

Turn both stops in a full turn (ie to where they were adjusted to).

Tighten the lock nuts.

This procedure ensures that the stops are just contacting the pressure plate when it's fully withdrawn, so braking it as designed. I found that adjusting like this gave a noiseless upward change and selection of first from neutral - downward changes of course are a different matter, and in fact the stops tend to make this worse.

Huge thanks to those who chipped in - hopefully someone will find it of use.

Cheers

Andy

[singleminded]

Now all I need is the correct method for the 1932 clutch ..John

[Andy Cubin]

Nice one Ian

[iansoady]

I don't think that method of adjusting the clutch stops will work.

What I did, after analysing what they were supposed to do, was this.

1. Screw both stops out till well clear of the clutch plate when raised.

2. Put the gearbox in top, hold the clutch lever right in, and screw one of the stops in until you can feel some drag through the back wheel when rotating it. This means the stop is contacting the pressure plate. It also requires 3 arms.

3. Unscrew this stop a full turn and repeat the process with the other stop.

4. Turn the stop you originally adjusted in a full turn (ie to where it was adjusted to).

5. Tighten the lock nuts.

This procedure ensures that the stops are just contacting the pressure plate when it's fully withdrawn, so braking it as designed. I found that adjusting like this gave a noiseless upward change and selection of first from neutral - downward changes of course are a different matter, and in fact the stops tend to make this worse. As a neophyte myself I suspect that not withdrawing the clutch completely for these would help but haven't tried it.

WRT pressure spring adjustment, I am blessed (cursed?) with the single spring type so the following is based on other marques but long experience of multi-spring clutches suggests that in many cases even pressure is achieved when the spring nuts look differently adjusted as the springs will have worn / lost their temper to different degrees. The best way I have found is to arrange a pointer which is nearly touching the pressure plate, and rotate the clutch (again with the back wheel in top gear) with the clutch raised. You can then see any wobble and adjust the springs accordingly.

[Andy Cubin]

Morning Beamers.

I have put together a clutch adjustment guide, the sources being the Motorcycle Manual and the Book of the Sunbeam.
Can you look through the following and add to the script so we collectively produce a definitive guide on how to preserve our gearboxes?

Also attached is a picture of the clutch bridge with what appears to be a locking screw (marked with the red arrow) - anyone know where it comes in the proceedings if at all?

The Script:

SUNBEAM CLUTCH ADJUSTMENT

1.   Clutch bridge
The clutch adjusting screw with lock nut is in the centre of the clutch bridge.  This screw holds the ratchet (clutch-operating) lever up against the push rod.  This rod pushed the outer plate on the opposite side of the box, releasing the pressure on the clutch plates.

This screw must be adjusted so that the ratchet lever is just free without excessive looseness.

Adjust clutch-adjusting screw until the operating lever that hangs down has appreciable slack in it.

To do this, detach the shackle that attaches the clutch cable to this lever.

The ease the locking nut and adjust the centre screw in or out as required.

The adjustment is correct when the operating lever has 1/8" play with the cable detached.

Once the adjustment is correct, tighten the lock nut.

2.   Clutch Cable
Once the operating lever has been correctly adjusted, excessive slack in the operating cable can be taken up on the small adjuster screwed into the front of the gear box bridge.

This should be set to allow a small amount of movement on the handlebar lever, when the clutch is engaged.

Because the bike has clutch stops on the primary chain case, the clutch cable must not be adjusted too tightly, otherwise the clutch pack and cover would come up against the stops before the plates have separated during gear change.

3.   Spring Nut adjustment.
If there is insufficient tension on the plates, it will be necessary to increase the spring pressure.  This can be done by removing the aluminium clutch dome to give access to the spring nuts.

Each nut should be tighten to an equal number of turns.  Do not overtighten as this will cause the clutch to be very stiff to operate.

4.   Clutch Stop Adjustment.
With the handlebar lever pulled in, screw in the clutch stop screws until they just touch the cover plate, then screw back 1.5 turns before tightening the locking nuts.

All input hugely welcome.

Cheers

Andy