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1955 NH gearbox oil change

Posted: Thu Sep 05, 2019 11:40 am
by CylvaBirch
Could someone please advise on the oil change frequency for the GB gearbox used on my Red Hunter?
I have found the drain plug using a big mirror. I cannot seem to find the change frequency, my manual just says to check the level and top it up. How much oil is required?
Thanks in advance,
David.

Re: 1955 NH gearbox oil change

Posted: Thu Sep 05, 2019 4:06 pm
by dave.owen
I rarely change it, just top up as required.

Dave

Re: 1955 NH gearbox oil change

Posted: Thu Sep 05, 2019 6:49 pm
by chris.shearwood
CylvaBirch wrote: How much oil is required?

Hello David,
Mr.Haycraft says: "All 1952 and later Burman boxes have an oil level plug located also on the kick-starter end casing; to top up the gearbox to the maximum permissible level, it is only necessary to pour in engine oil through the filler-cap orifice until it begins to trickle from the level plug hole."
He goes on to say the oil should be changed every 3,000 miles and the capacity is one pint.

Re: 1955 NH gearbox oil change

Posted: Thu Sep 05, 2019 7:17 pm
by JohnnyBeckett
what oil do you you use if you use EP oil it tends to get water in it and rust the box in side when the box gets hot and gos cold if you ride it daily it drys the out if not i use GP 50 OIL and its ok engine oil got a rust preventer in it

Re: 1955 NH gearbox oil change

Posted: Fri Sep 06, 2019 1:39 am
by nevhunter
While the original recommendations were engine oil it's a long time since the formulation changed due the environmental effects of additives and catalytic converters. Modern engine oils do not suit gearboxes anymore. Tractor oil universal does and also OK for the forks and hydraulic and wet clutches, and it has additives for storage corrosion effects and there are specialist gearbox oils for off road bikes with separate gearbox oil set ups.. Particularly if you run a Chair (sidecar) and you use the gears a lot I would be going out of my way to find a suitable better oil. Nev

Re: 1955 NH gearbox oil change

Posted: Fri Sep 06, 2019 8:47 am
by CylvaBirch
My old owners handbook says to use Wakefield XXL which is Castrol XXL. That is a straight 40, other options seem to be straight 50. Does it matter which? I know not to use modern gear oils as they attack the copper-bearing alloys in older gearbox designs.

Re: 1955 NH gearbox oil change

Posted: Fri Sep 06, 2019 2:12 pm
by JohnnyBeckett
use GP 50 it is better for a old gearbox

Re: 1955 NH gearbox oil change

Posted: Sun Sep 08, 2019 8:06 am
by CylvaBirch
I bought a litre of GP50 at Netley Marsh yesterday. Has anyone added a bit of molyslip to their gearbox oil? It is common practice on Moto Guzzis
The drain plug is hard to reach isn’t it?

Re: 1955 NH gearbox oil change

Posted: Sun Sep 08, 2019 11:33 am
by JohnnyBeckett
you can ad molyslip if you need to lots of old gearbox use engine oil instead of EP or HP oil and molyslip was used a lot in old gearboxs

Re: 1955 NH gearbox oil change

Posted: Mon Sep 09, 2019 7:43 am
by Mike Nash
Ah, Molyslip!
Long ago & far away circa 1962 I had a Matchless V twinned Brough sidevalver (prob of 1932) which had spent its life pulling sidecars and then a builder's box full of cement, etc. On my first couple of runs at high speed it tightened up, and me being young and impressionable, I put Molyslip in it; it never tightened up again. Convinced of its value I then put it in the gearbox (a Norton I think) and when the clutch cable nipple came off at the gearbox end during a long journey I didn't find it out till I got home when we came to a stop; I'd been changing gear without the clutch because the box was so smooth! How much was due to the Molyslip I'm not sure - one get's in tune with a favoured bike so easily and so deeply - but with those earlier cheap oils I think Molyslip had its place.
Today? Well, we're told that modern oils don't need such stuff but then the manufacturers always said that. Perhaps such additives still have a place for extreme conditions.
Regards to all, MikeN.