Just getting back into bikes with a TR6, but I've always run all my old cars and four stroke bikes on 20-50, and preferably the late lamented Duckhams Q20-50 eg my first 4-stroke was a Tiger Cub and last a '52 Guzzi Super Alce 500 single.
These days I just buy Unipart 20-50 from my local Unipart outlet, which is what will go in the TR6. Most of these oils now say "suitable for the older engine" ie motors either not built, or no longer, to the tolerances of modern stuff. Maybe if the engine's just been rebuilt one could use a synthetic.
As a pal of mine said "check the spec of a modern cheap supermarket 20-50 - it's way superior to the 'quality' 20-50s we bought as kids". Oil technology has improved, but we're still running the same sort of machinery!
#420779 - 02/25/129:52 pmRe: T140 Engine Oil - Which do you use? UK residents*
Not all 'car' oils contain friction modifiers which are supposed to be the cause of clutch slip.
Check the label for the JASO rating of ma or mb. Japanese motorcycle manufactures felt the SAE rating was not serving the needs of motorcycles with wet clutches and developed the JASO standard. The ma series does not have friction modifiers and mb does.
It is oil viscosity that supports the load applied by the connecting rod. The viscosity recommended by the manufacturer takes into account their ability to control the surface finish and accuracy of the rod journal. While these old rod crank journal feel smooth they are actually a series of bumps and tears. The oil must have sufficient viscosity to support the rod bearing above these abnormalities or the bearing will fail prematurely. Keeping this in mind Triumph, and most British motorcycle manufacturers of the day that used plain bearings, recommended 20/50.
#420783 - 02/25/1210:19 pmRe: T140 Engine Oil - Which do you use? UK residents*
Joined: May 2007 Posts: 1,831R Moulding
BritBike Forum member
I have a friend in the UK with a similar T140 with shared primary. The local bike shop sold him a synthetic motorcycle oil. The clutch started to slip almost imediately. It only stopped after the plates were removed and cleaned and the bike run on Castrol Classic 20/50.
#420792 - 02/25/1210:52 pmRe: T140 Engine Oil - Which do you use? UK residents*
For those of us in US I recommend Classic Oil Supply of Richmond VA (# is 804-261-4140). They stock Miller oils. It is a one man operation and the guy there, Bob Bauer, really knows his stuff. He also has classic bikes himself (BSA etc). HTH
#421314 - 02/28/123:03 amRe: T140 Engine Oil - Which do you use? UK residents*
Reg Allen's use Morris oils on the service but I top it up with Morrison's 20w/50. I used to have Tesco's 20w/50. If it sounds sacriligious, there isn't much by way of quality 20w/50 oil easily available. I used to use Castrol then (my fave) Duckhams but for a good few years now have struggled to find a quality 20w/50.
Shell X100 20W50 is a similar quality mineral oil to Duckhams. You can get it in Shell garages or if they haven't got any in they should be able to get it. I have used it several times in my 67 and because it is api SF it will be fine in a T140.
It certainly is a shame that T140s can't benefit from synthetic oil which is what I use in my 67 mostly these days.