Globs wrote:

The Bern wrote:happy enough using Castrol GTX 20/50

20/50 is a multigrade oil, i.e. not as slippery as synthetic.

The exact lessening of grip on a wet clutch will depend upon model, usage and oil, it's not a black and white science.

The 750 sounds lovely however, can we see a pic?

Yep, but back in the 70's synthetic were unknown

Or the clutch could have been designed to work with multigrade oil (T140V spec was ... 20/50)

Soz, no pic's of my own bike, but was US spec (peanut tank &'harley bars') same as below ...

ooohh, very nice Bern, bet you wish you'd kept that one?

XMax400Paul wrote:

The Bern wrote: Why is using "regular car oil" a problem for 'bikes with a wet clutch ? My 750 Triumph Bonniville was happy enough using Castrol GTX 20/50

Car Oil often contains friction modifiers that may cause clutch slip - most car engines have a separate clutch...
Car Oil can suffer from 'shear' forces from a motorcycles gears / gearbox... cars tend to have a separate gearbox / gearbox oil...

Yep, but I can't think of a car that uses a wet clutch

Yep, but I've owned cars with a seperate geabox where the gearbox is specified the same 10/40 semi-synthetic as the engine, in fact on the Frontera B the 4WD transfer 'box also used 10/40


The 'trick' is to ignore preconceptions & read the manufacturers manual/spec' sheet

horobags wrote:ooohh, very nice Bern, bet you wish you'd kept that one?

Sure do Mark, brand new out of the showroom was a great machine, went out to buy a 500 Daytona, went home with Bonnie

I bought a new Bonne in 1976,terrible reliability/warranty back up,bought my first Jap bike in 1977 and I have owned oil Triumphs since then I love them.Think synthetic oil appeared in 1960s American high performance cars me thinks

XMax400Paul wrote:Halfords Branded Oil is Made by COMMA, who also make CASTROL...
.

not quite but close enough


comma own the castrol name and will sell castrol oils through the same places that sell the comma oils
the oil is made in different places
used to work in the trade so delt with them on a regular bases


ps wilko oils are also comma

One think I would say,contradicting myself in a way lol. I would stick Full Synthetic Castro’s two stroke oil in my Suzy Kettle as it stopped it smoking! But m6 Little James 250 had to make do with Halfrauds own brand

Had a Morini 350 the valves needed doing every 1800 miles a change to semi synth and
when checked 10000 miles later they were perfect, a Greeves with a Villiers 2t in it ran
for thousands of miles without any problems at all on half the recommended mix but
using fully synth 2t oil.
Only things I am not keen on is fully synth in a wet clutch engine and changing to modern
oils in something that as been run a long time on older oils incase the detergent properties
of modern oils stair up trapped muck.

Castrol GTseX, the high performance lubricant

Ralph wrote:Had a Morini 350 the valves needed doing every 1800 miles a change to semi synth and
when checked 10000 miles later they were perfect, a Greeves with a Villiers 2t in it ran
for thousands of miles without any problems at all on half the recommended mix but
using fully synth 2t oil.
Only things I am not keen on is fully synth in a wet clutch engine and changing to modern
oils in something that as been run a long time on older oils incase the detergent properties
of modern oils stair up trapped muck.

I won’t use semi or full Synthetic oil in any of my other older bikes,20/50 in the R80,10/40 in the Hondamatic and HD oil in my Softail.I received an email/link for “bargains” and motorcycle oils don’t seem to be discounted