Castrol Answer My Question

Hello Everyone,
New to the site, but not new to motorcycles of all types,
I am posting this just hope it will help others out there
re-commissioning a 1967 unit 650 bonny, (last run 43 years ago)
and needed advice on which modern oil to use,
the more i read on various forums, the more inconclusive the replies,
so I emailed Castrol Classic oils for their advice,
I have copied my email to them for your information
Hi Guys,
Really getting confused by all the contradictory info on web sites as to "what oil"
The bike is a 1967 T120 unit Bonneville standard engine,
being recommissioned after a 43 year lay up
been given a refresh jobbie, piston rings, valves, springs,
gaskets, rewire electronic ignition, etc-etc,
fitted a "Norton" oil filter in the return oil line, put in 3 pints of GTX to start the engine
for purposes of setting carb balance, and strobe timing ignition, now completed,
and ready for filling with the permanent lube oils,
the owners forums i have checked failed to give a definitive, consensus reply,
suggested oils vary from 20w50 mineral oil, to 20w50 fully synthetics,
whilst others say an in line oil filter requires a high detergent oil
20w50 diesel engine spec oil, to allow particles to be held in suspension
for being trapped within the paper element of the filter,
another suggests a 20w60 grade ,
what i need is a clear unambiguous recommendation, what are the most suitable oils
the bike being a classic will be for summer days rides, at 55-70 mph,
The gearbox oil (1967 book) specifies a straight 50 oil,
the forums mostly suggest 80/90 gear oil, there is confusion around
damage to the bronze bushes inside the gear box,
which some owners have had experience of
due to the additives in gear oils by various manufacturers,
my question, which modern Castrol oils are best suited

THIS IS CASTROL'S REPLY
Good morning Clive,
The engine on the Bonnie runs on Castrol Classic XL20w/50,
which is a mineral low detergent oil,
you do NOT require high detergent, and synthetic oils may leak over time,
the unit construction gearbox used to run on Castrol Classic GP50 which is fine,
however you can use Castrol Classic EP90
as it is a GL4 specification and will NOT affect yellow metals,
I would NOT recommend 80/90 as again it will be a synthetic,
and at 80 weight will be too thin
The primary requires an SAE 20 oil
therfore use Castrol Classic TQF

All can be found at www.classicoils.co.uk
Kind Regards
Trevor
Castrol Classic Oils Manager

(All word for word reproduction) hope it helps others.

 

Hi Brian G
(Trevor was the Castrol Mgr who replied)
This post is my first is by Clive1
But yes the sludge trap is clinically clean as are all oil ways,
but thanks for your comments
have already ordered the classic Castol oils recommended

 

Hi Brian,
I started this renovation 30 years ago new rims st st spokes a bespoke exhaust and fitted a T140 front end with a single disc,
than somehow put the project aside and threw a blanket over it,
and that has where it remained until i had to shield because of covid 19
and out from hiding it came, and i have hardly come out of the workshop in months and is now 90% complete, a few bits and bobs then finding a quality nickel plating company preferably electroless nickel plating then a full nut and bolt rebuild and away we go,
looks now as if the first ride out will be next spring