Gear Box lubrication

[BUNNERS]

What is the general opinion of using Semi Fluid grease in the Burman GB gear box? I have used it in my 55 Speed Twin, 46 Matchless, 57 Matchless & AJS with no complaints.

[simon.holyfield]

I intend to use it in my Huntmaster. I use a Castrol LM mix with 20W/50 engine oil in the BA fitted to my SQ4, and it seems to be very happy.

I am happy that the GB design is similar enough to use semi fluid grease in that as well.

[pete.collings]

The first GB boxes (1952) used grease, and had a leather washer at the drive end to seal the box.
Later boxes were oil lubricated, and had an oil seal assembly at the output end.

I have in the past brought a partially dismantled GB box with congealed grease inside, horrible to clean out but with the gear and selector mechanism in good condition, whereas I have seen oil lubricated gearbox internals red with rust where water has accumulated inside and been left to stand.

[BUNNERS]

Two very interesting replies, two up for the grease at the moment. leather or seal what is the difference, if it keeps it in all the better.
Started the Hunt master today, it had lounged in a mud hut in South Africa for the last god know how many years, ye ha, happy days.

[david.anderson]

Nicholson in his book Modern Motorcycle Engineering advises that grease/oil in a GB box can be substituted for oil.
The GB in my 57vh leaked oil from the mainshaft oil seal not long after I had renewed the oil seal. I went to the grease oil mix initially as a quick fix. That was over 40 years ago and well in excess of 100,000 miles. I have used the grease/oil mix ever since (and have replaced the oil seal). The grease oil mix also leaks a lot less around the kickstart shaft
David

[ColinPeck]

What sort of mix ratio are people using, trying to delay a gearbox re-build for a while I would like to give this a go.
Colin

[roger.attwood]

I see Colin didn't get an answer to his question on oil/grease ratio for gearbox lubrication. Can anyone give me an idea of the ratios, as I'm ready to fill the box. Thanks
Roger

[Leejm]

50/50 mix. Or just buy some semi fluid grease which is basically the same thing but without the hassle of mixing it.

[Brian.Fosh]

I mix engine oil, normally sae40 with LM grease but sometimes use moly grease instead or empty a tube of Molyslip in to the mix if I find the selectors feel a bit stiff when changing (e.g if the fork faces are known to be a bit worn).

I aim to get the mix so it can just about slump and self level, for which I find it often needs more oil than I expected from the 50-50 start point.
I Then pack it in a polythene bag and fill the box like icing a cake.

When I want to change the grease (Only works If the box has a drain screw).. I top it very full with oil and take it out for a spin first so it runs out more easily.

I rebuilt/restored a SQ4 Dec 1950 Gearbox last year that had gone unused since the 70's and it had an oil seal at the sprocket end. But it was filled with what seemed, after so long, like grease alone. I turned new bushes etc. I noticed its Main-shaft oil helix stopped much shorter of the sprocket vs the late thirties gearbox that i'd opened at the same time. Consequently, the bushes in the sleeve that drives the sprocket were more worn on the later Main-shaft at the sprocket end.

I concluded that while we none of us like leaking boxes, it can be advantageous to err towards a little runniness in the oil/grease mix to be sure it can reach within and through all the bushes.

I attach a photo of the two SQ4 mainshafts here. The upper shaft is from the Dec 1950 gear box and the oil helix stops where the shaft wear noticeably starts midway between the two bushes in the final gear. This is the shaft I used, but I made the end bush a tight fit over the unworn shaft, pressing the final gear on but it freed up just perfect as it reached the worn end so I don't have any excess clearance.

The older (lowest shaft in the photo) has the helix go right up close to the sprocket end and is notably free of any excess wear.

[paul.jameson]

A word of warning on these 2 mainshafts. The later one (with the long splines for the clutch) has a different main diameter length from the earlier one to compensate for the bush in the centre of the gear which runs on it at the kickstart end. If you mix the two up, you can engage two gears simultaneously which will strip the teeth off one of them, at best. I found this out the hard way on CP boxes in the 1990s.