B52 Gearbox

[Kerb]

Greetings from New Zealand! I've recently purchased a 1952 16MS that hasn't been used for around 15 years. After fixing the oil leaks and other assorted problems I've finally got it running, but have found that it's not possible to select 4th gear. With the bike on centre stand in 4th and not running, I can hear a slight clicking noise from the clutch side of the gearbox as I rotate the rear wheel. Examination of the selector cam doesn't show any obvious problems, can anyone advise me what's likely to be causing the problem?

[Mick D]

Hi

It sounds as if you can select it when the engine is not running so things that are likely to affect selection when the engine is running are:

Poor clutch adjustment
wear of the clutch tangs and slots
Incorrect primary and secondary chain adjustment

Are you failing to select fourth when riding or just stationery with the engine running?

Regards Mick

[Kerb]

When it's not running and I turn the wheel it sounds as though the gears are on the verge of engaging, when the running there is nothing there when I put it into 4th

thanks, Kevin

[Mick D]

Hi

Get someone to turn the rear wheel in the direction of drive whilst you push down on the foot change, does it go into gear now?

If the bike was running OK 15 years ago I'd suggest the fault is potentially corrosion in the gearbox preventing the sliding gears or selectors from moving to their full extent.

I think a gearbox of this vintage would have been grease filled - shine a torch down the filler port, do things look OK / greasy or corroded / wet / dry?

Regards Mick

[Kerb]

The gear box had a decent amount of oil in it when I drained it ( this model doesn't use grease), and have refilled with fresh SAE 50 after opening up the outer case. Turning the rear wheel while pushing down on the foot change makes no difference. I have already dismantled the clutch and there were no apparent signs of wear on the tangs or slots, adjustment is ok and it functions well in a road test in the other gears. Primary and rear chains are correctly adjusted.

I'm guessing that I'll have to take the inner gearbox cover off and check the movement of the sliding gears and selectors.

Kevin

[Mick D]

I'm guessing that I'll have to take the inner gearbox cover off and check the movement of the sliding gears and selectors.

Hi

That would be my next step. Check the drive dogs for burrs, wear, play or distortion of the selector forks, wear of the selector shaft pins, corrosion of the sliding sections of the main and lay shafts.

Regards Mick

[Kerb]

Thanks Mick, it will be a good challenge to take everything out and figure out how it all goes back together! I haven't dismantled a gearbox since I owned a Triumph in the 1970's

[SPRIDDLER]

Welcome to the forums Kevin.
There are a couple of articles on o/hauling the Burman B52 gearboxes in this link:

http://archives.jampot.dk/technical/Tra ... on/Burman/

This is one of them:

http://archives.jampot.dk/technical/Tra ... Owners.pdf

There are details of transmission service on page 42 of the Owners Manual here:

http://archives.jampot.dk/book/Owners_m ... Manual.pdf

And workshop manuals here:

http://archives.jampot.dk/book/Workshop_manuals/

[dave16mct]

I think some early B52 boxes need a shim behind the main bearing to fix this. Do a search under B52 shim.
Dave.

[Kerb]

Thanks for all the links Spriddler, gives me a pretty good picture of how to go about this. I had started thinking that it might be worn selector forks but it seems that this would most likely result in jumping out of gear rather than a false neutral. I will check out the need for a shim behind the main bearing, thanks for that idea Dave. I'll dismantle the box next week when I have time, and hopefully all will be revealed.

Kevin