Ok - so I've been reading my owners manuals and even grabbed a copy of the service manual off the net, so I'm FAIRLY certain where I stand on this now, but I thought I'd post it in here for others information - and just in case I'm WRONG (Which does happen with monotonous regularity!). ANYWAY - Obviously I ride a 2010 Yamaha XVS650A Custom. While riding today - a short blat from the office where I work to one of our off-site buildings (<1km) I suddenly felt a 'pulsing' on my left ankle/heel when I pulled up at the lights. Look down and, what I now know is the straight plug, was missing from the center of the left crankcase cover. I nursed the bike back to the office and parked it. My left heel had a sheen of oil on the heel. Not massive, but enough that I knew I wasn't riding till this was resolved as it couldn't be a good thing to be riding with a hole there! I went for a drive in the company jeep along the route I'd taken. I KNEW that the hole wasn't there when I started my journey earlier, and there was only one short path I'd taken and...yup...there it was lying in the middle of the road. I grabbed the straight plug, returned to the bike and re-screwed it back into the crankcase cover. Seems it had just worked its way loose. Probably why we should always give our bikes a once over before riding! I know this is one area I'll be sure to check in future on a regular basis! In the mean time - Oil levels - yes I know, they DO need to be checked. I've not had the chance (yet!) - it was too dark and I had no one to hold the bike level for me. That said, I will be checking this in the morning. As I didn't have great quantities deposited on my boot, or see huge spills on the road where the plug had come out or where I'd parked the bike while looking for the plug, or see it ejecting great sprays as I nursed it back to the office, I figured there was enough to get me home, but I did nurse it all the way. No freeway and no mad acceleration. I'm not OVERLY worried at the moment. Tomorrow morning I'll check the levels and if need be, drive the cage down to the local garage for some oil to top her up with. Anything else I should do, should have done?? Comments, etc...?