Burman B52 Gearbox help please

[56G80S]

Its 20-25 years since I refurbished my B52 box and I did it by the method that you probably use, although I didn't have a 'phone camera then. Notes. sketches and even an incompetent like me managed to end up with a working box which indexed correctly.

I did make a lash up of mating a CP clutch to it but it all worked. There's no end float on mine either (I refitted the "incorrect" but slicker AMC box and put the GB on the shelf)

Good luck, there are lots of people here who will help and are knowledgeable - I'm not the latter though.

Johnny B

[nomisimon]

I don'r remember there being any end float on the selector cam either...but I can't see anything missing or that has changed. The cam is held by bushes at each end, which when the cover is fitted, end up with no end float. I can't see that there have been any shims or spacers fitted, nor do the exploded diagrams show any. I was fully prepared with 'phone camera and notebook when I realised I may not have to dismantle the box. I've looked at the various gearbox articles people have recommended on here and the gearbox does look relatively straight forward.

Hopefully there is someone who knows these boxes inside out.

Thanks

Simon - who should be showing as a member now.

[nomisimon]

The problem is almost certainly the end float on the selector cam shaft...it's moving about an eighth of an inch as I mentioned earlier.

Others say they have virtually no end float, pictures of the GB / B52 box indicator show it almost flat against the case. When I push mine flat against the case the gearbox seems fine until I let go.

This isn't a rotating part, like the main shafts, so I'm sure I could use a spacer, washers etc to take up the play.

Is that a sensible solution?

My worry is that everything was working before, but I can't see any missing or damaged parts.

There is also a discussion on the Ariel Owners Club Forum regarding this very problem...but they don't recommend a specific solution.

What are your thoughts?

Thanks

[Mick D]

Hi

In my experience there should be little axial play of the selector cam, as you say this is governed by the shouldered bushes installed in the inner and outer covers. Both bushes are fitted 'from the inside' and as such are restrained in use.

Selector Bush Inner.png

Selector Bush Outer.png

You are going to need to investigate why you have excess end float which will require removal of the outer cover and selector cam. I suggest you undertake a full strip down of the gearbox, if you do it in situ and don't need to remove the sleeve gear it can be completed in less than a day and without special tools. Take the opportunity to replace worn parts and seals as required.

Regards Mick

[1608]

I have mentioned before that end or axial play on the selector shaft can make a crucial difference, even fitting a thicker gasket as some people have done thinking it will help stop oil leakage can make a difference. There should be virtually nill end float. There is bound to be internal wear on the selector and end play on the shaft simply exacerbates the problem. The symptoms you describe suggest that the selector is only barely reaching far enough. To test this theory, before stripping too much of the box try eliminating the end play by use of some washers or shims as an experiment and them try selecting. Another cause further into the box can be bent or distorted selector forks if memory serves me correctly.

[nomisimon]

Thanks Mick D and 1608.

I already have the cover off and there doesn't appear to be any damage to the selector cam, case or any other component; I'll take some pictures and put them on here.

With the cover on 'as-is' the selector indicator is too far out from the case, judging by what I remember and pictures of other boxes. The regular paper gasket is fitted.

When I turn the gearbox, there is a clicking noise that I think is the dogs almost engaging judging by the frequency of it. The indicator moves in and out a bit in time with this. If I push the indicator in by hand, to where it would normally sit in relation to the case, the gearbox turns freely without any nasty noises; and a little end float is fine before the noise just starts.

With the cover off, the selector cam can move further out and the gearbox locks, as I would expect it to.

The end float is massive...at least an eighth of an inch and I can't see why it would be there...unless some form of spacer was fitted which has somehow disappeared. I realise there is no spacer shown in any of the various diagrams.

I believe this is all that is wrong with the gearbox, although I will make further checks.

Having watched YouTube videos and looked at photos and diagrams, disassembly of the gearbox is no longer daunting...the problem is that I have a temporary ileostomy which makes sitting on the ground to address the gearbox uncomfortable. If the box is OK I'd rather leave it alone for now.

The gearbox was rebuilt along with the rest of the bike about 14 years ago...it hasn't done many miles as I've been unwell for some time.

Let me take some photos and possibly a video.

[SPRIDDLER]

Gearboxes aren't really my thing as I've not had much need to rebuild many (everything else!) but could it be that when you select a gear the pinions aren't staying engaged and the noise is the dogs clicking.
This article which describes the B52 selector action may not be of any specific help but since you aren't getting very far a read of it might just trigger another train of thought.
The title suggests it's about the gearbox 'jumping out of gear' due to wear/damage to the spring loaded cam plunger which holds the selectors/gears in engagement but your problem may be related since you haven't been able to ride it to try it out and discover if the gears don't remain engaged.......

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

[nomisimon]

Hi Spriddler, thanks for that. I've been through all the technical articles in the archive.

I'm almost certain that the problem is quite simply the end float on the selector cam. I just need to work out what might have changed as there is no apparent damage to anything, nor is anything apparently missing. As I mentioned, when the selector cam is pressed home the gearbox seems fine. All the gears select correctly when I do that.

I'm going to take another look tomorrow...and will seek a suitable spacer if need be.

My list of bits to fix the aftermath of the dynamo sprocket parting company with its shaft isn't too bad so far. The dynamo is off to be fully reconditioned...it had never been done and the magneto was done a couple of years or so ago. I need an 18/21 engine sprocket, a couple of chains, a spring or two and a few other bits and bobs.

*** If anyone has a moment and a selector cam unit not in a gearbox, that fits the GB/B52 box, I'd be interested in the measurement of the shaft section that fits between the two bushes.

I also need to clean and repair a couple of dings in the gearbox surfaces where the outer cover gasket goes. I suspect that's why it was filled with a grease / oil mix...although I do know that is an option anyway.

I went for a ride on my modern Honda yesterday; fast, smooth, reliable but just not the same feel good factor...and very heavy. And they put the brake and gear lever on the wrong sides!!!

[Mick D]

Hi

You need to remove the cam - take out the two split pins from the selector shafts and withdraw the two cylindrical pegs from engagement with the cam.

Selector Removal.png

Do your bushes look the same as the ones in the photos above?

Does your cam look like this?

Selector Cam.png

Regards Mick

[SPRIDDLER]

This isn't a rotating part, like the main shafts, so I'm sure I could use a spacer, washers etc to take up the play.

Is that a sensible solution?

Your earlier comment above has been niggling in the back of my mind.
I think you've moved on (back?) from considering that fix but I'll mention anyway that I wouldn't do that since there's clearly something that needs attention and if the 'box locked up again it could result in serious damage or even have you off the bike.
But I expect you've come to that conclusion already.