Burman B52 Gearbox help please

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

Postby Mick D » Sun Oct 11, 2020 3:49 pm

Hi

It doesn't matter which way the bearing is fitted and your temperatures will be fine, I smear a little grease around the outer race to ease it's fitment before I put it into the freezer in a poly bag.

I habitually fit bearings so as I can see the part number without removal ;)

It's easier to fit the seal to the carrier first then fit the assembly next to the bearing and retain it with the circlip. The oil seal fits so as when it's assembled to the gearbox you can't see the garter spring.

Regards Mick

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Re: Burman B52 Gearbox help please

Postby nomisimon » Sun Oct 11, 2020 4:13 pm

Hi Mick

Thanks...I'll migrate the bearing to the freezer ;)

I also fit components so I can see the identification...mostly vintage electronic ones.

I suspected that's how the oil seal was fitted, but I saw a guy do a video of a CP box stripdown and his was the other way; should I tell him? :shock:

Regards

Simon
Thank God for Southby

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Re: Burman B52 Gearbox help please

Postby nomisimon » Fri Oct 16, 2020 6:17 pm

Almost there I think.

The two bushes for the mainshaft driving gear, part number 19-8-13, were somewhat worn. I've made up a tool which I used to pull out the bushes using a long bolt.

The originals are made from 'Oilite' I believe, some form of sintered phosphor bronze. Basically, it's slightly porous to allow oil to get through, albeit in small quantities.

This is the main driveshaft for the back wheel so does quite a bit of work. I bought a pair of replacement buses from the club and they look like a solid, brass material...without the porous qualities of the original. There are no oil tracks on the inside of the bushes and I wondered if they are as good as the original or do I need to fit NOS items?

Once this is sorted, there are a few 'dings' on the mating surfaces of the outer case, then I'm good to reassemble the box.

I do, of course, need the dynamo back before I build everything back up.

Regards

Simon
Thank God for Southby

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Re: Burman B52 Gearbox help please

Postby Mick D » Fri Oct 16, 2020 6:54 pm

Hi

As you will have seen, the sleeve gear bushes are rather thin walled, when installed they may deform to the point where the main shaft will no longer pass through them and will require reaming. The main shaft has a diameter at this point of 55/64", (please confirm your is the same as mine were), and I'd suggest creeping up on this dimension with an adjustable reamer. When reamed aim for 0.004" clearance.

I don't think you can still get sintered bushes for this location, plain metal will be OK as long as you allow adequate clearance.

Regards Mick

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Re: Burman B52 Gearbox help please

Postby Group Leader » Fri Oct 16, 2020 7:35 pm

I know nothing of the dimensions/details of this bearing other than Mick mentioning 55/64" so my post may be a lot of nonsense (no change there I hear you cry!) but a quick Google and the first UK hit seems to have a very large range of such bearings. Maybe one would be suitable?

https://simplybearings.co.uk/shop/Beari ... tml?page=7

Alan
1953 AJS 16MS, 1939 BSA 250 and a 1/3 scale Sopwith Triplane but that's another story ..... :lol:

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Re: Burman B52 Gearbox help please

Postby Andy51 » Fri Oct 16, 2020 7:45 pm

I fitted club sleeve gear bushes to the B52 'box on my 18S some years ago. They were solid bronze, not sintered, but I cannot remember if they had spiral oil tracks. I fitted them in the gearwheel, mounted it in a 4 jaw chuck and bored them out to fit, about 2 thou clearance. Phil Irving recommends 2 thou, but reckons up to 6 thou wear is acceptable. Hope this helps, Andy.

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Re: Burman B52 Gearbox help please

Postby nomisimon » Fri Oct 16, 2020 8:54 pm

Hi Andy - thanks, they do look like bronze. There is definitely no oil track in either bush...there were none in the originals either. The originals were definitely past their best although possibly usable in an emergency. I'll fit them and see how freely the assembly slides over the main shaft, depending on the availability of some others, see below.

Hi Group Leader - that's a useful website, maybe the ones I have are oil filled? They look just like bronze (or brass) to be honest. These bushes are particular to this type of gearbox I believe.

Hi Mick D - yes, they are somewhat thin walled. There is little difference in the outside diameter of the new bushes when measured against the old ones. The shaft measures 21.8 mm (55/64 inch) where the bushes run and the new bushes do have some clearance. All I can do is fit them and see how they feel. I have some adjustable reamers that belonged to my late father but I'm not sure if they go that large.

I have ordered a pair of what claim to be NOS bushes, from Norbert on eBay; a french seller. They were just £3 each and may be a more suitable solution. He may also not send them: I bought three items from him, one was a selector cam as mine is worn. The one he sent was quite chewed up on the outer shaft and when I requested a return, he wasn't happy that I wouldn't return it outside eBay. The other items were perfect, so hopefully he was just having a bad day. If he sends them, I'll wait until they arrive before deciding.

The old bushes were knackered...quite a lot of wear and hence clearance. The inside surfaces had black recesses in spots too.

Regards

Simon
Thank God for Southby

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