Hello, I have a 1956 B31. The kickstart jams solid occasionally. Not like it's in gear and will move the engine a bit, but really solid. I put in 2nd gear, roll it a few inches, and it unjams. I have replaced the ratchet pinion. I have also fitted a Phil Pearson electric start, but it still jams occasionally exactly the same with that. So it must be a problem in the gearbox?? Any ideas? Thanks
A standard BSA gearbox issue. You can lessen the effect by grinding a lead-in on the first tooth but you'll never eradicate it completely.
The problem, that I have come across and fixed completely, on two gearboxes is worn ratchet teeth and worn bronze bush that fits on the end of the mainshaft.
The kickstart quadrant itself was not worn.
No grinding of teeth required
There are two types of ratchet teeth, early flat top and pointy and you cannot mismatch them.
Some people have had really worn plain steel top hat shaped mild steel bush on the inner cover and the plain bush on the outer cover which, in my case, was not a problem. It can all be remedied by removing just the outer cover, even leaving the gear lever and selector forks in situ and the kickstart lever whilst you inspect. I believe '56 would be pointy gear type.
When I get chance to pull out my spares books I can give you the precise part numbers.
Edit button has gone so:
Early pinion and kickstart quadrant are 67-3168 and 67-3178 (flat top gears).
Later pinion and kickstart quadrant are 67-3376 and 42-3160 (pointy top gears)
Phosphor bronze bush between mainshaft and kickstart pinion is 67-3169
Steel inner kickstart spindle bush 67-3151
Steel outer kickstart spindle bush 67-3153
You can use either matching pairs of pinion and quadrant it does not matter I have pointy ones on the GS box and flat ones for the competition box.
To be fair magazine road testers commented on this issue back in the 1950s, and I doubt wear would have been an issue on new bikes.
I can only comment from my direct experience of getting them to work
Maybe the pointy version was an upgrade to rectify the jamming issue?
I believe the problem is caused by the top of the leading tooth on the quadrant landing on the top of one of the teeth of the mainshaft pinion. Presumably making them pointy would make this less likely to happen - until the teeth wear. My old 1948 B32 has the lightweight 4 speed gearbox and suffers from the same problem. The only answer is to select a gear, rock it back and forth a couple of times, go back to neutral and try again.
Thanks for the quick reponses and very useful info.
One thing I don't (yet!) understand is why is it happening when the kickstart quadrant is not engaged with the ratchet, and I'm using the electric starter?
Ok
Now I am confused.
The electric start fits between the electric motor and the crankshaft, I do not believe that the gearbox is in the power line?
I presume that you have to disengage the clutch when you start the engine or just in neutral so the mainshaft spins?
But as you say the kickstart quadrant should not be in contact with the ratchet.
The kickstart issue you describe is common and not attributable to an internal gearbox problem.
Hi,
This sounds more like a selector problem and for some reason the box is trying to engage two gears at the same time or the selection is not being completed.
Could it be an issue with the selectors or the plunger?
Dave.
Hi there
Neil- Normally I have it in neutral when I use the electric start, so it follows that if there is a fault in the gearbox the mainshaft could be jamming? .... So I tried the electric starter 7 times with the clutch disengaged just now. It started fine each time, so that may be a temporary solution. Normally with the clutch engaged and in neutral, it would jam about 1 in 4 or 5 times.
Dave- I do have a false neutral when the bike is cold when changing up between 2nd and 3rd. It seems to clear once it has warmed up- not sure if that could be part of a selector problem that could be causing it?
Thanks
Hi,
General wear and tear will affect the selector function. But it may be worth checking the plunger that helps to keep the selector plate in place. Items 64 to 67 for the plunger and 48 for the selector plate for the swinging arm type gear box. The plunger is adjustable to increase/decrease pressure against the indents on the selector plate.
Dave.
OK thanks...I won't be able to get onto it for a few weeks but will let you know if I discover anything