Hey everyone, this is another post about a recently rebuilt '09 GS500F. Very briefly for those unfamiliar: I spun a crankpin bearing last October and fully rebuilt the engine on my 2009 GS500F with 34k miles (see full post here: http://gstwins.com/gsboard/index.php?topic=73944.0). After rebuilding the bike, it was a bit smokey on initial startup. That problem has since resolved. I've also noticed a top-end ticking noise which I posted about here: http://gstwins.com/gsboard/index.php?topic=73967.0

Today, a new fun issue has arisen. I recently returned from a 10-day trip out of town. During that time, the bike sat in the garage and was not operated or ridden by me or anyone else. Today, I checked the oil level, which was good -- and oil was golden, which I expected after only 600 miles since the last oil change. However, the after riding the bike around town for a few miles, it's clear that the engine idling very weakly. This is a significant change from my pre-trip rides. Sounds as if it's going to sputter out and die. If I give it throttle, it comes back to life. My first thought was a compression issue. Read on, because the plot thickens.

To complicate things, there appears to be an itty bitty bit of oil leaking from the junction of the left carb and the left intake. Here's a photo:
https://i.imgur.com/YH1sEUM.png

Of note, the same oil beading exists near the right intake, but it's not quite as severe:
https://i.imgur.com/Ja9sHGe.png

This oil does not appear to be as golden as the oil I observed on the dipstick when checking the oil level. Quite the opposite actually:
https://i.imgur.com/Vc8TX6R.png

Not really sure where to begin with this one, aside from removing the gas tank, carbs, etc. and poking around. I'm currently at work, and I just had the idea that maybe the clamp which secures the rubber seal around the junction between the carb and the intake might be loose. I might try to tighten that with a screwdriver when I get home and see if that solves the problem. Seems like fuel vapors escaping may explain the lack of a steady idle.... or would it be the opposite? Would additional airflow into the intake (from a loose seal) cause the bike to idle at a higher RPM?

My other concern is that there shouldn't be oil in the area of the intake to begin with. Could it be a bad valve seal on the left intake? Or both intakes? This would be very surprising, given that the valve seals are basically brand new with less than 900 miles on them. I'm hoping this doesn't end up being too much of a headache. I'm concerned that the top end of the bike might be in bad shape 

Would really appreciate any advice!

Do the spark plugs have any oil on them?
That's the easiest way to start checking for oil in the combustion chamber.

Your carb looks like its coated in old oil which makes me think its been doing this for awhile, you just haven't noticed it before.
If oil really is leaking out of that spot and not dripping down from somewhere else I'm guessing you have bad valve seals but that is weird since you just replaced them. Maybe you replaced them wrong somehow or got some of that carbon-off solvent on them. I thinking sitting for 10 days gave the oil in the head plenty of time to seep into the combustion chamber through the bad seals. Did it not smoke on startup after your trip?

Are you burning a lot of oil between oil changes? Mine was using a liter or more of oil every 1,000 miles. After new rings and valve seals it uses a liter every 3,000 to 4,000 miles.

The weird thing is that intake boot should have a good enough seal to prevent a vacuum from the engine...so oil shouldn't be able to leak out. Did you replace the intake boot and o-ring when you did the rebuild? The oil leaking out could be its own issue that is also showing you that you're carb doesn't have a good seal to the engine.