Sure you can, if you let the engine idle for around 5 minutes your oil temps should be over 100 degrees. The question is why warm up your bike at all, if you think about it the oil has already drained into the bikes oil pan for quite awhile so all the oil that could possibly drain from the top end of the engine is already in the oil pan. The oil may drain out slower but you have plenty of time to let it drip into the catch pan, starting the engine will just pump the oil back into the top end and then you have to wait for the top end to drain out again.