Burman B52 Gearbox help please

Information relating to the Matchless G3 or AJS Model 16 350cc Heavyweight
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Mick D
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Re: Burman B52 Gearbox help please

Post by Mick D »

Hi

I'm not a fan of just adding spacers to achieve seemingly correct operation, something has happened to cause this condition and I strongly suspect it was due to the shock experienced when the transmission locked.

Spacing the cam inwards will have the consequential effect of moving the cam away from the gear lever selector fork and could introduce problems in that area.

I appreciate that sitting next to the bike may be difficult but once the gearbox is stripped the majority of the investigative work can be done on the bench. You say you have the cam out so there's only the main shaft nut, kick start ratchet and inner cover screws to remove and you're inside the box.

I'd find out what's gone wrong and fix it properly.

Regards Mick
nomisimon
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Re: Burman B52 Gearbox help please

Post by nomisimon »

Hi David16mct - possibly. I found what looks like a new old stock selector cam and have ordered one.

Hi 1608 - when pushed inwards, the selector cam sits in exactly the right place, the gearbox turns smoothly and quietly, the gears select properly. The washers are only for the outer cover side of the selector cam :)

Hi Mick D - that was my thought, but the transmission didn't lock...the primary and rear wheel chains went tight. The problem presented is down to the end float on the selector cam...the bushes look ok, the selector cam looks ok and so do the covers. The bushes are also in the correct place. I agree that something has caused this but with the outer cover on, a fraction of a millimetre pushing the selector cam shaft inwards stops the noise. The end float is about an eighth of an inch and I suspect it may have been like that since the box was rebuilt. I'm not a fan of what is effectively 'putting a plaster on' but without the end float there is no problem. When the selector cam shaft is pushed in, the gear selection is perfect and the indicator has the correct spacing from the case. The cause of the excessive end float is a quandary...if you look at the photos I took and compare it with the others, nothing looks awry apart from a small amount of wear which I'd expect.

Having said that, I have ordered a new gasket for the inner cover and don't see any harm in looking inside. I have to wait for the dynamo to come back anyway and it would, as you infer, give me peace of mind. I can also take a proper look at the main bearing...which I believe was replaced previously, but bearing in mind (no pun intended) that the parts to stop the dynamo nut were never fitted...who knows!

I really appreciate all the help from everyone on this...thank you.

Simon
Thank God for Southby
nomisimon
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Re: Burman B52 Gearbox help please

Post by nomisimon »

I've carefully dismantled the gearbox now...despite assurances to the contrary, I don't think anything has been touched in here since the box was new. So, taking it apart was a good idea Mick D and others.

The various gears look totally undamaged, as do the rest of the innards so far. The main bearing feels and sounds a bit noisy and looks original. I think it should be replaced as should the front bearing.

The box is now a shell with just the main bearing installed. What is the procedure for removing this bearing, and can it be done with the box in the bike?

Regards

Simon
Thank God for Southby
56G80S
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Re: Burman B52 Gearbox help please

Post by 56G80S »

From memory, that bearing is an odd one. It's a mix of metric and Imperial. Back in the day when I refurbished my B52 I had to have the centre bored to fit the shaft.

I think they are more easily available now. Others will know.

Johnny B
Mick D
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Re: Burman B52 Gearbox help please

Post by Mick D »

Hi

Johnny's correct, the bearing is an odd size and hence more expensive than most. It can be replaced in situ, you just need to be able to heat the gearbox case, (I use a hot air paint stripper for these type tasks), and source suitable tubes, (sockets), to drift the bearing in and out.

If you haven't already removed the sleeve gear you may need a chain wrench and suitable socket or tube spanner to do this if you can't lock the sprocket using the rear brake, this is a bit of a challenge by oneself, get a pal to assist, the sprocket nut should be torqued to around 60 LbF Ft

There's an oil seal on that bearing which will need to be replaced. When I restored the gearbox on my FH Draganfly was offering an overhaul kit comprising of all gaskets, seals, oil, Wellseal, the two ball bearings and a £20 voucher - it was a bargain.

Regards Mick
nomisimon
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Re: Burman B52 Gearbox help please

Post by nomisimon »

Yes, they are a special bearing but the correct one, and the bits to go with it, are available from the club.

I have a great heater which I will point at it, once I've cleaned out most of the grease/oil mix...not strictly the right lubricant on a 1955 box I believe.

I've already removed the gear...I spent a couple of hours trying to find a suitable socket for the nut, eventually ordering one on eBay for £15 including postage. On a hunch, I knocked the tabs flat and put an old adjustable spanner on the nut...it was barely finger tight!!!

I plan to replace the bearing and all the associated bits; oil seal, clip spacer etc. And the bearing at the other end of the main shaft. The Draganfly kit purports to be only for Triumph, Ariel etc; I suspect it may be good for my bike too so have asked the question.

I'll also get the mainshaft checked to make sure there is no runout, and check the bushes...which look OK visually.

What I need to know is, how to get the bearings out of the cases once they are heated up. The kickstart end looks straight forward, but there is an old circlip on the drive end, followed by the oil seal, oil seal housing and bearing. There are no rings for my circlip pliers, so do I just lever the circlip out? After that I assume the oil seal and housing should come out, followed by the heating of the gearbox housing before using my sockets to carefully knock out the bearing.

The bearing is, as I said, the original I think and sounds dry and roughish...you can feel it too.

Simon
Thank God for Southby
Mick D
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Re: Burman B52 Gearbox help please

Post by Mick D »

Hi

Have a dig around, there should be holes in the circlip - see photo:
GB44 MS Brg.png
Failing that dig it out with a 90 degree pick and order a replacement. Once the circlip is out the oil seal comes out with the holder - it will probably be held in with muck, then heat the case and drift out the bearing.

There is a sprocket spacer that runs on the lip seal and may still be in place - make sure you remove and save this.

I'd be interested in Draganfly's reason for that statement.

Regards Mick
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nomisimon
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Re: Burman B52 Gearbox help please

Post by nomisimon »

Ah hah...I didn't see the holes for the muck. I'll take another look tomorrow. I do have the spacer.

Once everything is cleaned up, I'm going to replace anything that looks iffy; I'm not keen to dive in again too soon.

I'll let you know what Draganfly tell me.

Thanks again.

Simon
Thank God for Southby
nomisimon
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Re: Burman B52 Gearbox help please

Post by nomisimon »

Hi Mick D

Draganfly said some of the bits in the kit were unsuitable for the Matchless...at the end of the day, it probably wouldn't have saved me a fortune in the grand scheme of things (see below).

I've just sent the club spares dept another £200 order for bits...obviously the main bearing and associated stuff. Lots of bushes and other worn parts. The oil cover on the clutch end of the layshaft is missing...I suspect it has been for years; that may explain the use of gunge rather than oil in the box. Basically I'm replacing anything which looks past its best.

It would seem that the selector fork on the mainshaft is very slightly bent...it is that, combined with the poor position of the selector cam, which was causing the noise.

So that's G-29-2 which 'may' be able to be straightened if I can't find another; thanks to you and others for pushing me to dismantle the box. It had seemed OK before the sprocket came off, but examination has revealed lots of other things which need doing.

I'm £360 in so far...plus the £260 or so for the dynamo...but I know it will be right.

Simon
Thank God for Southby
Mick D
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Location: Aberdeenshire

Re: Burman B52 Gearbox help please

Post by Mick D »

nomisimon wrote: the selector fork on the mainshaft is very slightly bent
Hi

Is it bent in the manner it would be if it was pushing the selector cam towards the outer cover? if so I would suspect the cover is slightly distorted outwards and it is this that is contributing to the excess play on the selector cam shaft.

If you're replacing the selector cam shaft bushes you could check the free play on the shaft afterwards by temporarily assembling the inner/outer covers and selector cam, this will give you a good indication of any distortion to the covers.

Have Fun Mick
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