Have a search for "what oil to put in a vincent"
You'll see there was a long discussion on what oil to use some time ago - have a search for the thread I mention above.
I use 15/40 and have just suffered catastrophic cam failure - however whilst lubrication is one possible reason, we don;t yet know exactly what has happened.
Many riders use straight 40.
Some use 20/50 (especially in the States - gets hotter)
Some use synthetic (whilst others say its wrong)
Bottom line is that my advice would be to ask around, read the thread, talk to people you know (15 different people and 15 different opinions) and then make your own mind up.
At this moment, I think I am likely to stick with 15/40 mineral oil.
Best of luck,
Regards
Stuart
Hi all, this is my first post here. I did some searching but came up empty. I was wondering if 15w40 would be ok in a black shadow, for engine and gear box? Thanks. Warren