Kickstart/gearbox irregularity.

I have a 1974 MK IIA

When taking off from a dead start the kickstart lever pulls back.

If I let off the gas it comes back up to it's normal position.

The only time this happens is when I accelerate from a dead start. when I accelerate from anything but a dead start everything is fine.

When I first noticed this several years ago I went to my local Brit bike mechanic and had him inspect the gearbox. Everything looked fine. Since it was apart he converted to the roller bearing.

Any ideas about the source of the problem?

Could it be as simple as a weak kick start return spring?

Hmmm, sounds like the layshaft inner bearing is not doing it's job, but you said you had it replaced? Interesting. What make/part no. bearing was installed?

On second thought:
It could be a weak spring or a spring that is not totally preloaded, as the 1st gear set is closest to the kick start shaft and the gear reaction load would be carried mainly by the bushings in the kick start shaft.

regards,

Derek

I bought the roller bearing from British Marketing.

I'll order a spring and see what happens.

I would check the layshaft to make sure it is not bent. Did you have a bearing failure that caused you to replace the layshaft bearing? If so you may have more damage.

Also check the bush inside the kickstart shaft. As I have said on this forum before, replacing the layshaft bearing without replacing the kickstart shaft bush is only half the job. It is a real pain, so many ignore this, but if there is movement here, you have the same problem. If you have changed this bush, was it reamed to size? If the shaft is too tight in the bush, you might experience this sort of behavior also.

I found it quite amusing when I watched the late John Hudson chase a gearbox all around the workbench on the NOC video. But I was disappointed to see him not even address removal or replacement of the kickstart bush.

In any event Arch, attend to this soon, as having the rear wheel lock up at speed is pretty dangerous.

Arch,
if you're still around...found your post and it describes a problem that just started to appear on my '74. Same thing - droop back on first gear acceleration, a little on 2nd, none on higher gears.
Wondered if you found the cause?
Mebbo

That problem is generally caused by the failure of the layshaft bearing so needs to be investigated immediately.

The original ball bearing fails catestrophically with the cage disintergrating first followed by the balls exiting the bearing. Once these balls are loose they can get between the teeth of the gears and jam the gearbox locking the back wheel, pulling the clutch has no effect :evil: . After mine went I took the gearbox apart and found the balls some in pieces in the bottom of the box, so I was very lucky.

:cry: Bummer! Thanks, guys - looks like a tear-down job. Having just rebuilt a '48 BSA box, at least I know I can get a bearing in and out!
Mebbo