Author Topic: S6 Dragging Clutch  (Read 160 times)

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Offline PaulW

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S6 Dragging Clutch
« on: 15 Mar 2019 at 23:34 »
I've recently bought a 1930 S6 together with quite a lot of used spares.  The bike hasn't been used for 10 years, but having dropped the old oil, cleaned all the gauze filters and oil pump, cleaned up the magneto, changed the tyres etc etc, she is now up-and-running and sounds nice.

But what I haven't been able to do is stop the clutch from dragging.  I cannot select a gear while the engine is running and back wheel is not turning...without a crunching of the gears.  If the back wheel is turning (i.e. on the centre stand), there is no problem at all.  I've had the flywheel off half a dozen times, and have cleaned and checked the two rows of rollers and ball bearings.  I've also checked for a nice sliding fit of the bearing shell onto the flywheel central hub.  I've tried several different clutch plates.  I've also checked the clutch cable length, the clutch arm angle, and the three roller plate that the arm rises on.  The thrust ball race seems fine and I seem to have all the correct thrust washers etc.

Without the engine running, if I pull in the clutch lever, then I can freely kick the kickstarter i.e. clutch is disengaged.  I've not messed with the 4 speed box, but have topped it up with fresh oil / grease mixture; all gears are easily select when rotating back wheel.  When I replaced the flywheel, I lubricated the clutch bearing etc via the central grease nipple.  Could my grease be too thick?

I'm not sure what I'm over looking, so any help and/or advise would be gratefully received.

Paul
Dorset

Offline Eric S

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Re: S6 Dragging Clutch
« Reply #1 on: 16 Mar 2019 at 07:31 »
My bike is a 1937 600 aero and had the same problem with the difference that the rear wheel was always turning at neutral and engine at idle.
After a lot of investigation I noticed that the flywheel/shaft cone surface was getting worst and worst and that the shaft coming out of the engine was loose. Cone bas been rebuilt and hope to be able to put engine back together in the next couple of weeks...

Offline douglas1947

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Re: S6 Dragging Clutch
« Reply #2 on: 16 Mar 2019 at 18:37 »
Paul,
have you checked the clutch cam / lever for using the complete way to disengage the clutch?
The 3 rollers for the cam use to wear.
Is your clutch plate / friction plate really straight?

Michael

Offline PaulW

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Re: S6 Dragging Clutch
« Reply #3 on: 16 Mar 2019 at 21:56 »
Thanks Michael and Eric.

I think I have found the problem.  As I had access to a 1930 T6, I compared the two flywheels / clutches; T6 is on the left and S6 on the right:



Everything looked identical until I examined the flywheel-side thrust race.  On my S6 version, there is step which protrudes into the roller area.  This step is deep enough to foul the rollers when the clutch is operated and also prevents the race sitting on the sprocket.  On the T6 version, the underside of the race is perfectly flat.

S6:



T6:



Having tried the flat T6 thrust race, everything is now working fine and I can select gears without crunching them.  But now I have two additional question:

1) Any idea what this stepped thrust race comes from?
2) Any idea where I can obtain another good non-stepped flywheel-side thrust race?

Many thanks for your help

Paul