XR600R oil flush - car oil ok?

Having changed my XR engine over I was going to give the oil system a flush and brief run and then change it and the filter out again.

For this brief run (5ish minutes) is it ok to use some cheap car oil I've got? Or will this cause clutch contamination issues? Or should I just stick to more expensive bike oil for flush duties?

Answers on a postcard please.

Never tried that, but I wouldnt trust it. Remember when you drain the sump some oil is retained in the head, filter etc. And who knows what effect it will have on the clutch plates, as you said it could be absorbed and cause slip.

I doubt cheap car oil would have the expensive friction modifiers that good quality car oils have, so I'd use it. The oil contamination of the clutch won't last forever if you're just running the engine up to clean rebuild debris out. This clutch slip thing is a recent wobbler that people get on their high horse about, years ago everyone used car oil with no problems. Nowadays as there are bike specific oils available I'd be inclined to use them as normal day to day oil, but to just clean and flush a rebuilt motor and dump it out after a few minutes running, cheap car oil will be ok.

Cheers, I'll give it a run through, hopefully it'll be up and running by the end of today.