Burman B52 Gearbox help please

[nomisimon]

Afternoon gentlemen. I have already removed the selector shaft pegs and the selector cam...pictures to follow. Everything looks the same as your's Mick D, except a bit more worn.

IMG_0486_1024x768.JPG

This is the bush on the outer cover.

IMG_0487_1024x768.JPG

The selector cam in place

IMG_0488_1024x768.JPG

The bush area on the gearbox body

More next...

[nomisimon]

Here are a few photos of the selector cam

IMG_0496_1024x768.JPG

IMG_0495_1024x768.JPG

IMG_0494_1024x768.JPG

More follows...

[nomisimon]

Finally two images showing the end float on the selector cam and therefore indicator and selector shafts...and one of the length of the area between the bushes on the selector cam.

IMG_0489_1024x768.JPG

IMG_0490_1024x768.JPG

IMG_0497_1024x768.JPG

Spriddler, the gearbox has never locked up...I just get a clicking sound when rotating the shaft, which moves the indicator on the selector cam shaft at the same time. The shaft and indicator are sticking out of the side of the gearbox more than they should, and more than they were. If I push the end of the selector cam shaft back to where it should be the gearbox rotates freely and quietly. There should not be about an eighth of an inch of end float on the selector cam shaft. The two bushes do not look damaged, the case isn't damaged, the selector cam looks OK so unless the person who built the gearbox fixed a component issue with a spacer during assembly, I'm at a loss.

Can anyone confirm the corresponding measurement on their selector cam, shown in the last picture?

This is quite odd.

[Mick D]

Hi

That's a mystery, I can't see anything wrong with your components

Just been out and checked the GB gearbox on my FH. There is about 0.015" clearance between the gear indicator and the outer case, pushing the indicator inwards I get about 0.010" movement, (against the detent spring), but I don't think the indicator is bottoming out.
Is your indicator standard and do you have the small spring behind it?

Before you dis-assembled the gearbox did your indicator look similar to mine?

Indicator.png

Regards Mick

[nomisimon]

Hi Mick.

Yes it did, although it stuck out further from the case unless I pushed it in...at which point it looked just like yours.

Ten thou sounds about what I'd expect, not what I have. I made a short video showing the movement but it's too large to post here.

When the dynamo sprocket came off, I heard the noise and was only going slowly. I pulled over immediately, let the engine stop as I pulled the clutch in and was eventually recovered by a big yellow truck.

When I got home I found the dynamo sprocket loose, the dynamo chain snapped and sitting up on one of the oil directing flanges. The primary drive chain and rear chain were as tight as a drum...because the primary chain had been dislodged and was riding on the edge of the drive sprocket. It had come off the clutch sprocket and was on the body of the clutch itself. I had to lever it off the drive sprocket at which point everything slackened off. There will have been quite a bit of opposing radial load on the clutch and drive gear...I did have the presence of mind to pull over quickly and nothing seems bent or damaged.

I will check the gearbox carefully before riding out.

It's almost as if there was a spacer or washer, about an eight of an inch thick, on the outer case end of the cam selector which has somehow vanished.

Currently there is no spring behind the gear indicator...I know it should be there...I may have lost it when I took the beastie off; but don't remember it. I will buy a new one. The spring would make the problem worse of course, not better.

It is quite a quandary!

[SPRIDDLER]

Spriddler, the gearbox has never locked up...I just get a clicking sound when rotating the shaft, which moves the indicator on the selector cam shaft at the same time.

Sorry Simon, my confusion. On checking back I realise I was incorrectly remembering your early post below but that was with the cover off.

With the cover OFF, the cam can move further out and the gearbox locks...presumably two gears selected at once.

As you say, a bit of a mystery at the moment.

[1608]

The gear shift shaft bushes in the inner and outer covers look worn to me. A little bit of wear on each of the components in the train to do with the selecting / indexing all add up and short of renewing said parts the first thing I would do is add shims or a washer to compensate for the wear on the bushes to see if this helps. If so new bushes may be the answer. I don't see the sense in stripping the box ( it can be a fiddly job putting it all back together) until you tried the simplest remedy. Adjusting the end float on my GB box sorted my selecting problem.

[nomisimon]

Hi 1608

I've actually ordered some 3/8 steel washers which I hope will fix the problem.

There is a little wear on the bushes but not enough to give 1/8 inch of end float.

I didn't rebuild this gearbox originally so I'm wondering if the selector cam is the original; hopefully someone will have a shaft they can measure.

There are a few little niggles with the bike which I'm going to work my way through; various rubbers, headlamp glass rotating etc.

I love riding it and have just ordered about £80 worth of bits to sort the damage caused by the dynamo sprocket, from the club spares shop.

Very easy to use, even though it looks a bit out of date

Thanks

Simon

[dave16mct]

Hi Simon,
I just measured one and its 46.33mm. So not much difference, less than 1mm. But along with worn bush flanges it might be enough to cause your problem.
Dave

[1608]

Hi Simon, I know this may seem a little obvious but only supplement the bush in the outer cover so the shaft is pushed further into the box.