Gearbox oil

 Dear All

As promised a quick update.

As I mentioned previously my rebuilt box has been filled with the Penrite T250 Transoil SAE250 gear oil and has now been returned to its rightful place. So far due to weather and life I have only managed to do one short test run and then a longer one at just over 50 miles. I can't say that the thicker oil has stopped the crunching of gears, but it certainly has made the changes smoother. There are also some other factors at play such as the having matched gears selector detent springs and a rebuilt 4th gear, which has also made the general gearbox experience much better. The biggest improvement in reducing gear crunching was by being more careful when matching gearbox and engine speeds. This is a skill that I think will take a bit of practise that I am looking forward to learning.

I think my conclusion would be that it is not the viscosity of the oil, but the skill (or lack of) that is the biggest factor in a quiet gearbox.

Below is a picture of my machine, "WA" at the Sammy Miller Motorcycle Museum. The museum was the halfway point on my longest run (50+ miles) to date. Very pleased!

 

has anyone used   penrite semi fluid and steering box lub.   some use it on vintage gearboxes  ?

"Penrite Fluid and Steering Box Lube" is advertised as being suitable for Burman motorcycle gearboxes. It's meant to be a semi-fluid oil/grease gunk, liquid enough to self-level.
Perhaps Penrite hasn't heard of Sopwith, an ignorance that I suppose we have to shoulder.
Anyway, it's plentifully-available on-line, at about £17 per half-litre.

BF's gearbox was originally treated to SAE250 gear-oil, in the hope (unrealised!) of stopping leakage.
The viscous drag of this oil was such that BF had to be stood in front of a 1kW fan-heater for 45 minutes before there was any chance of kick-starting it on winter mornings.
Now however, the SAE250 liquid toffee has been replaced by a litre of 'Morris's K400EP Semi-Fluid Grease'.
This is the middle-option of three EP grades of self-levelling grease, otherwise K40EP or K4000EP.
Surprisingly perhaps, viscous drag is now much less: I think that the gear teeth cut paths through the lube, which doesn't immediately flow back.
Another bonus is that leakage is 99% a thing of the past!
This elixir of gearbox bliss comes in 3 litre tins, for about £40, enough for 3 gearboxes. Time to form sharing-clubs of three?