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Motorbike gearbox fitted to a milling machine

Gearbox make horrible noises now and again

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malcolm hollins07/02/2022 16:42:14
34 forum posts
20 photos

The Mill I have has been fitted with a old motorbike gearbox as a way of changing the milling speed without the need to change the belt pulleys.

The gearbox is mounted 90 degrees to the position it would have been in a motorbike therefore the oil is not at the bottom of the gearbox. Now and again it make a horrible noise I assume that this is caused by lack of oil on some of the gears. There is also a a lot of oil getting on the 2 belts but I can not see any obvious oil leaks from the gearbox. What would be the best form of lubrication and how much should I use ? Would high melting point grease work? Thicker oil work? Filling the gearbox with lubricant

Nigel McBurney 107/02/2022 17:11:18
1004 forum posts
3 photos

pre ww 2 some gearboxes were lubricated with grease do not know the grade possibly near fluid grease ,post war my 1952 6E Villiers 197cc 3 speed gearbox was lubricated with straight 140 gear oil (not EP) later on my 9E and 32 A villiers gear boxes used straight 30 oil.Do not use any extreme pressure EP gear oils as the additives attack bronze. The oil on the belts probably comes from where the input shaft which held the clutch goes through the sleeve gear which held the rear wheel drive sprocket. cant remember how the sleeve gear was kept oil tight in the inside dia, the outside of the sleeve gear usually had a lip seal.

clogs07/02/2022 17:14:39
626 forum posts
12 photos

dump the oil and use an axle grease...HIgh metling point will be ok.....

remember thats all that lubs 4-9inch angle grinders.........

old mart07/02/2022 17:20:33
3913 forum posts
268 photos

If you get some WURTH HHS 2000 synthetic thick spray oil, you could lubricate everything in the gearbox without having the problem with leaking. The box would need to be dismantled first and all the old lubricant removed and a means of access to the insides for occasional spraying extra lubricant made. Some holes in the casing which could be sealed by rubber plugs would do. This Wurth oil is the best lubricant I have tried and works on gears as well as bearings, it clings very well.

DiodeDick07/02/2022 18:44:32
38 forum posts
9 photos

In the pre-war gearboxes I was familiar with, there was no oil seal, as such, between the sleeve gear (output) and the main shaft input, just a bush inside the sleeve gear bore. This was OK because the oil level was below the main shaft. There is usually a level plug on the gear box shell - this was often BSW thread as it screws into the alloy shell. Some had a hole through the the inner cover wall so that oil put in through the clutch lever. cover would find its way into the main box. A new sleeve gear bush would help, but if the box is noisy it may need more than that.


Chris Evans 607/02/2022 20:42:47
2069 forum posts

A lot of pre-war gearboxes and even late model Royal Enfields use semi liquid type "O" grease. This is also used in commercial vehicle chassis lubrication systems.

Pete.07/02/2022 23:10:08
815 forum posts
245 photos

Malcolm, the gearbox on my mill uses a recommended NLGI 00 grade semi fluid grease, it may cure your leaking issue, Ebay gearbox grease, if you can be bothered working out how to upload photos I'd love to see this motorcycle gearbox milling machine.

Hopper08/02/2022 01:34:13
6730 forum posts
348 photos

Yes, would love to see pics. What make/year of gearbox is it? Some can be upgraded with modern seals on the output shaft. Even turned on their side, most boxes should work ok as long as oil level is high enough to come up to the main shaft/gear level. Splash will take care of most of the rest of it. Lubing the bronze bushes is as critical as lubing the gears.

Grinding noise is unlikely to be a matter of lack of lube on the gears in a low HP application like this. Could be a ball bearing starting to fail. If so, replacing it with a sealed bearing would ensure it remains lubricated well enough for this low HP application. Norton gearboxes in particular are prone to the ball bearing on the end of the layshaft failing. This causes grinding noises as the balls all bunch up on one side of the bearing and the shaft goes out of alignment so the gears mesh all skew whiff. On a 60HP Norton Commando, the next  noise is a large explosion as the shaft fires out through the gearbox casing.

Edited By Hopper on 08/02/2022 01:48:43

malcolm hollins08/02/2022 10:18:55
34 forum posts
20 photos

I removed the gearbox from the mill and I was going drain the oil from it.

I undid a bolt that was on the bottom of the gearbox thinking it was the drain plug.

The bolt was unscrewed a little but it became very loose I tried to tighten it up again but it does not want to rethread .

When the gearbox is back in the Mill this loose bolt would be at the top of it so oil or grease might not leak from it.

I think it would require the gearbox to be stripped done in order to get the bolt tight again. I have no experience of doing this.

I am unable to insert photos of the gearbox and the Bolt. Tried to follow the instructions but could no find Insert in may Photo album using Windows 11.

Hopper08/02/2022 10:58:51
6730 forum posts
348 photos

Oh dear. It might be the selector cam pivot bolt. But never fear. Opening the box and tightening it up is no big deal.

See your other thread for details on how to post pics on this wacky site. Once you post pics and we can see what the box looks like, there are plenty of old bike guys on here to help out. If the box is making grinding noises, it needs opening up and inspecting anyway.

malcolm hollins08/02/2022 11:14:05
34 forum posts
20 photos

dsc04847.jpgdsc04845.jpgdsc04844.jpgHere are some phots of the gearbox and the Boltdsc04848.jpg

malcolm hollins08/02/2022 11:27:15
34 forum posts
20 photos

What is involved in removing the End Plate.

Which parts to I need to remove to get inside the gearbox?dsc04849.jpg

John MC08/02/2022 11:41:39
386 forum posts
45 photos

Early Velocette gearbox. Plenty of information on the net regarding dismantling the box. Some spares available, try Grove Classic motorcycles.

May have the same "innards" as the later velo gearboxes, if so then plenty of spare available, at a price!

No proper oil seals in those boxes, not even in the later versions but some owners of the bikes fit seals, seems to work well enough.


Hopper08/02/2022 11:48:21
6730 forum posts
348 photos

Aah, John MC has beaten me to it. Amazing the breadth of knowledge on this site. Was not a box I recognised. Must be pretty ancient? And no kickstarter? EDIT: Ah looks like that triangular blanking plate goes where the kicker was removed.

It looks pretty obviously like the four threaded studs sticking out are the bottom of the gear box and the labelled oill filler cap is showing which way is up. So the drain plug would most likely be the one sticking out at right angles to those four threaded studs, right at the bottom of the casing.

No idea what the bolt you have loosened up would be. Maybe another plug,judging from the copper washer, and the thread has stripped?

Does the gear lever spring back to the same central position after you shift gear, like a foot shift motorbike lever? Or does it (more likely) just stay in the position you put it, so sitting in a different position for each speed? And how many speeds does it have?

Edited By Hopper on 08/02/2022 11:50:04

Edited By Hopper on 08/02/2022 12:06:55

Hopper08/02/2022 11:55:18
6730 forum posts
348 photos

It looks suspiciouisly like the 250 Velo gearbox in this "how to rebuild" article that might be of help


Hopper08/02/2022 12:05:28
6730 forum posts
348 photos

This looks pretty similar too but has more detail **LINK**

If you google around for Velocette 350 MAC or 250 MOV there is a wealth of info out there, and new spare parts to by the look of it.

not done it yet08/02/2022 13:14:40
6891 forum posts
20 photos

Thinking outside the box a bit, but that box may be worth replacing with another option. Velocette parts are, I would guess, exchanging hands at premium rates, for good items, these days.

malcolm hollins08/02/2022 14:54:54
34 forum posts
20 photos

The loose bolt has 8.8 M GSF on it.

There is the number 9-15471 (From Hopper's link I think it is a pre war MAC)

The gear lever returns to is normal position after changing gear.

I read Hoppers link on the gearbox which was very good if you know all about them which I don't.

Can I remove the outer screws only to remove the cover to get to the other end of the loose bolt?

Michael Gilligan08/02/2022 15:11:21
20289 forum posts
1064 photos
Posted by malcolm hollins on 08/02/2022 14:54:54:

The loose bolt has 8.8 M GSF on it.

dont know

That merits investigation


Hopper09/02/2022 00:17:11
6730 forum posts
348 photos

No idea really other than what is in those articles as I was never a Velo Fellow. But in general on those old Brit bike gearboxes, yes you can undo the screws and remove the end cover off the gearbox to access the internals. Best done with the cover facing upwards so the shafts and gears stay in place. There might be some videos on YouTube that show how its done.

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