[shorrog]

One other thing that may be helpful. I put together a short video of adjusting the gear box selector mechanism and that can be found athttps://www.marston-sunbeam.org/technicalNotes/Model9GearboxAdjustment.html

There are also some photos of a three speed gearbox strip down and rebuild.

Graham

[shorrog]

This was the reply that Ian helpfully put together.

Welcome to Model 9 Ownership and to joining our prestigious club , You have inherited a very desirable Motorcycle , Lucky man.

However , running the clutch with only one clutch stop operating will give unequal pressure on the outer plate and can give rise to clutch drum bearing failure and could damage the gearbox  main shaft if carried out over a long period.  The clutch stops prevent graunching into gear but you must check the main shaft sleeve gear bearing to make sure the clutch assy does not wobble about, if it does you won't get a clean opening of the clutch and no attempt at adjustment will prevail.

If the clutch does not run true then the pushrod will foul the main shaft bore and cause excessive wear to both and be a cause of drag as both run at different speeds   

When all of the clutch components are correct including bearings the clutch will open freely and spin true without any drag at all and all bearings without wear , the clutch stops can be used with the lightest of pressure. It is best when starting off to pull the clutch lever in and COUNT TO  THREE and the gear will engage like a knife through butter, totally graunchless. This is providing that the spring pressures are equal and the plates are flat and true and the throwout ratchet adjustment is correct.

Maybe it would be best to get the clutch working properly before investigating your gear problem , The clutch stops are fitted with a hard red fibre insert , It is best to have both stops with the identical material and size otherwise the friction will differ across the clutch plate and the effect be unequal  friction .

There is a modification that is possible that avoids the clutch drag , main shaft pushrod problem, and avoids using the clutch stops altogether. But that can be for later,

[shorrog]

I have been coipied in on the following email thread and I am posting here as other folks may find the information useful.
Graham

I have just joined the Marston club and wondered if someone might be able to help me with a couple of questions/advice. I have recently inherited my grandfather's 1931 model 9. I am a motorcyclist but have very little mechanical expertise, and am certainly all at sea with this beast of a bike! It has been running, and I have done a couple of hundred miles on it over the summer, but now there are one or two of problems.



Firstly, it lost the upper clutch stop. Not realising that it had an important role (!) I carried on riding the machine. Was that a bad mistake??? Over time I found it was suffering from considerable graunching when changing gear and no amount of clutch adjustment helped any. Does that figure? Could I have caused some damage without the clutch stop in place??

Also, out of interest, what would the frictionless end of the clutch stop have been made of originally?

Anyway, I now have a newly made clutch stop and will try to set the bike up. What exactly does the clutch stop do??

The other problem is that it will no longer go into 3rd gear. Does anyone have any idea as to what the problem might be? Could it be connected to the missing clutch stop??