What oil would you recommend for an early R1 BEC?

Should I stick to bike oil, or is there something specialist that copes better with the extra strain and heat?

Stick to bike oil. The vast majority of car oil has friction modifiers in which will cause endless clutch slip. You'll probably want to use semi-synth as in my experience fully synth causes clutch slip in a bike, let alone a car!

As above, just use a good quality semi synthetic bike oil.

I use Castrol Power 1 in my Blade engine and have not had any issues (note that Power 1 Racing is fully synthetic, don't use that)

Yamalube 10w40 Semi Synth

I use putoline 10w40 part as recommend by a friend that has a bike tuning business a if that's anything to go by?!
https://www.ebay.co.uk/itm/301164892950
It had 10% off last time I ordered it.

Thanks gents -

I've often used higher viscosity semi-synthetic in preference to thin fully synthetic, since I destroyed a Subaru motor using 0/30.

I hadn't really thought about the wet clutch...

Cheers

Out of interest, is there a simple way to check the oil level in a bike engined car?
I have an R1 powered Phoenix and checking the oil level is not easy!
Cheers

I've always run my 5vy on fully syn oil with no clutch issues. I I finally used Valvoline 4t, then went to Silkolene comp4 but now on recommendation of the engine builder I'm using g Motul v300. He says virtually everyone on moto go and superbike grids is using it despite who sponsors them (hes currently Shame Burns mech).

I check the level hot at idle. 2/3 - 3/4 way up the glass. Just use a torch to see better but have seen people use an inspection mirror.

Thanks for your response (checking oil level), I think mine might be slightly full then as I can just see green (difficult to determine with the torch, mirror might be a better option)! I'm assuming that as the engine is mounted in a form of cradle that it would therefore sit at the correct angle?
I think the way forward would be to start again by replacing the oil with correct amount and then checking the sight glass (I miss dip sticks!).
Cheers

Original angle would be with the sump bottom horizontal. Every bec R1 I've seen has been canted over with the gasket face level. It's not an issue and quantity is usually standard +200-400ml (mines +200). I've also run it overfilled (topped up too much and been top of slight glass) without issue until it'd burned some off. Have a look at it running, cold and the level should be low. If it's still high then drain a bit.

Thanks, that does make complete sense, the sump is level although it has a different sump (baffled), and the angle does look right compared to how it would sit in a bike, as you say, I'll need to check it whilst cold!!!
Thanks for your help - clearly I'm still learning and I've got lots more to learn yet!!
John