Gearbox/Clutch Problem

[Maurice]

I took my 1934 Scott out for a short run (11 miles) and all was well. Having removed my kit I went to wheel the bike into the garage and the bike appeared to be in gear. However I was unable to select neutral. Upon looking at the detent it was in the neutral position. I then discovered if I lifted the clutch I could not depress the kick start without the bike moving forward. I can wheel the bike with the clutch lifted without turning the engine over. If I wheel the bike without lifting the clutch the engine turns over. I can see the clutch plates separating when I lift the clutch.
I suspect something nasty in the gearbox. Before I pull it all apart can anyone suggest what the problem is?
Thank you.

[dave bushell]

Make sure that the bolt that runs from front to rear on top of the gearbox is tight. This bolt holds together the gear selector fork which is in two parts. One part is the external gear selector quadrant and the other is the internal fork assembly. The two parts have a male “V” and a female “V” are held together by the through bolt. If the bolt is loose, the two parts disengage and you can’t select a gear or neutral.
Dave

[Maurice]

Thank you for the suggestion. Have checked, and nut and lock nut are in place and bolt appears correct.

[dave bushell]

I assume that you have tried putting the gear lever in other positions and also taken the inspection cap off the gearbox and checked if there is any gear movement when you operate the gear lever.
Dave

[Maurice]

Hi Dave (or anyone else with ideas)
I can move the gear lever to all three positions (four including neutral). I can see the gears sliding, through the cap.
With the clutch lifted I can rotate the back wheel without the primary chain moving.
With clutch engaged when I rotate the back wheel the primary chain moves in all four positions.
Seems I have lost neutral.
Cannot understand how that happens so guess I must remove gearbox and have a look inside.

[BRIAN MARSHALL]

Try putting the bike into SECOND gear, ensuring that the external bellcrank indent ball is in the relevant ‘hole’ in the indent plate, and that the second gear pair of cogs are fully engaged and in line with one another, with the dogs on the selector drum fully engaged into the back of the second gear cog. Adjust the length of the external linkage between the positive stop mechanism and the bellcrank arm as necessary. Hopefully this should sort out your gear engagement problems. Also put some more grease into the positive stop mechanism, to make sure that the ratchet and pawl mechanism is operating cleanly. One other thing to check is the tightness of the clutch centre retaining nut, and at the same time check that you haven’t got more than about 12 to 15 thou” end float on the mainshaft. I have a sneaking feeling that your clutch centre retaining nut has come loose……
Brian

[Maurice]

Thank you both for your suggestions. Brian hit the nail on the head. The clutch centre nut was loose.
Having tightened it all seems to be well but the weather is so evil I have not ridden it, merely run it on the stand.
It is quite difficult to tighten the nut as the main chain has to be off to get at the nut. What is the technique to hold things still while tightening?
Thanks again.

[BRIAN MARSHALL]

Now that I have pointed you in the right direction, I can get a bit more specific….. Do make sure that you have got a tab washer under the clutch centre nut, and when the nut is fully tightened bend one of the tabs onto the flat on the side of the nut. It you don’t do that it will soon loosen off again. To lock everything up solid whilst you tighten the nut is not particularly easy, and depends what equipment you have to hand. On a DIY basis, you can get the bike in gear and at 90 degrees to a wall, then put a couple of bricks or blocks of wood between the tyre and the wall, so that it can’t move. Somebody sitting on the bike holding the brakes on hard at the same time will also help. I have a clutch locking tool, which consists of an old clutch plain plate with a steel arm about six inches long welded to it at a tangent, but I don’t suppose that many people have got one of those !
There are of course cruder ways of locking things up, involving sticking lengths of wood between the chain and the clutch drum sprocket, but they make me shudder, and I won’t go into more detail !!
Brian

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