1950 g80s gearbox oil

[Baz]

Hi everyone, I'm a new member and new to British bikes so please bear with me. I believe my bike, a 1950 g80s has a Burman cp gearbox. What oil and how much is needed? There is a lot of different opinions on the Internet. At the minute it's got a pint of straight 50 in it, but the manual I have is from 1955 and I'm not sure that's right? Many thanks.

[Andy.S]

Hi Baz
Welcome to the club.
Early boxes use semi fluid grease the club spares sells it or try the link below.
http://penriteclassicoils.co.uk/product ... g-box-lube

[Duncan]

Hi Baz, and welcome to the club.

You will get lots of slightly differing views on this subject but SAE 50 is fine for these bikes, if that's what it has been running on keep using it however the oil seals on CP boxes are a bit primitive, early ones up to about 1948/9 were greased filled later used engine oil, many people used self levelling grease now sometimes with a dash of engine oil.

Have you discovered Christians Archive yet, You can access tons of period information there http://archives.jampot.dk/

[Duncan]

Hi Baz, and welcome to the club.

You will get lots of slightly differing views on this subject but SAE 50 is fine for these bikes, if that's what it has been running on keep using it however the oil seals on CP boxes are a bit primitive, early ones up to about 1948/9 were greased filled later used engine oil, many people used semi fluid grease now sometimes with a dash of engine oil.

Have you discovered Christians Archive yet, You can access tons of period information there http://archives.jampot.dk/

[Douglas Campbell]

The manual for my 1948 G80 with a CP box indicates one pint of summer grade engine oil. 50 grade is perfect

[g80csp11]

couldnt see the 1950 Matchless manual , but AJS will be the same and answer most of your questions

http://archives.jampot.dk/book/Owners_m ... Manual.pdf

[Les Howard]

Yes as other have said SAE 50 engine oil is fine but should you really want a gearbox oil you can get Millers Classic Gear oils with some extra benefits in the formulation (anti corosion for one thing) : https://www.millersoils.co.uk/products/ ... -90-gl1-3/ and also slightly thicker to reduce leakage: https://www.millersoils.co.uk/products/ ... 140-gl1-3/ Note: Gear oils use a different number scale for the same equivalent engine oil viscocity. Compare the figures horizontally on the chart I show. Also note EP oil is not really suitable for old gearboxes as the straight cut gears do not generate EXTREME pressure anyway, especially when in top gear as the input shaft and output shaft are locked together via the "sleeve-gear" dogs and there are no cogs/gears actually transmitting power through their teeth...they are just spinning idly in the oil...

viscosity.jpg

[Baz]

Thanks for the really helpful information and quick replys everyone, it's really appreciated. At least I know I'm not damaging my gearbox with the oil I've use and I'll get that millers gearbox oil ASAP. Thanks again.

[spookefoote1956]

I use semi liquid grease in my B52.