B175 1970 Gear Oil Question

[bluewater1150]

Hi, I'm in North Northumberland (Alnwick area) and I've just bought my second Bantam, the first was a D7 in 1968 - I feel like I've gone full circle... There have been Triumph twins, BMW's etc etc but now I've come home!

The manual says SAE 40 or a 20/50 for the gearbox/clutch oil. I've also read that 'modern synthetic oils' are not recommended and can cause clutch slip, something to do with 'friction modifiers' and not great for a wet clutch. Have I got that right?  My question is about the SAE40 oils, I've found a good outlet Smith & Allan, they sell a 40 non detergent and a 40 low detergent oil - classic motor oil, which is the better oil for a Bantam. Thanks for any advice.
 

[rhyatt]

I have used S & A oil for years.
Good value and friendly people to deal with.
I have 3 x D7 and 1 x D14 and use their sae40 basic monograde.
Upside is 25 quid a gallon can does all 4 bikes.

[bluewater1150]

Hi, that is good news indeed. Just to confirm, do you use the non or the low detergent SAE 40?

Another quick question on spark plugs, is there any real advantage on using the Iridium NKG BR7EIX over the B7ES, I know they are a good plug, but are they 'that good' at more than twice the price?

[rhyatt]

I use SELECT sae40 in all of them

Iridium - frankly , I don't notice any difference - I carry a few ordinary spares with me

and the main bearings lubrication don't forget

yes must use the right oil in our bikes whether it be sae 40 in the humble bantam or more modern 10-40 motorcycle specific oil in more modern machines - as you say our clutches swim in oil and oil is meant to reduce friction - which a clutch needs to work.

so right oil is a must

detergents were used to carry internal muck around and keep the internals clean - then at oil changes the muck was dropped out - there are schools of thought about which to use , but I have always use the FREE


https://www.smithandallan.com/product/smith-allan-select-sae-40-detergent-free-classic-motor-oil-4161

[V500]

Back in the dim and distant past the oil you put in the Bantam (or any other bike's) gearbox was what your dad had in his garage. No ill-effects were ever noticed.
Super-slippy modern stuff is best avoided now, but most other oils would be suitable for the low stressed Bantam gearbox.

[Mark Cook]

There are many other suppliers of straight 40 oil.

https://pesltd.uk/?product=GF40  for example.

Mark

[bluewater1150]

Thanks for the advice. I've gone for the S & A non detergent Select SAE 40 classic oil, arrived next day which is amazing at this time of year.
I do remember what V500 says, about using what oil was available is your Dads shed, somehow they seemed to do the job, mind my old D7 had a slipping clutch problem that never really got fixed, we used to re-cork the plates in those days, maybe that was the problem or maybe the wrong oil...

[rhyatt]

yes, S & A are my go-to for oil these days , for all of my cars and motorbikes - as you say next day arrival