This applies to all Honda Gold Wings, BMW's and other horizontal opposed engines.
I had rode cross country one hot summer. My buddy rode his GoldWing and sometimes it
would smoke after being parked 10 minutes to an hour.
I have been working on these bikes since the 1970's and have seen many of them do this with
very low miles and even with new valve stem seals and rebuilt motors.
First of all make sure there is no fuel in your engine oil and be sure that the oil is not over full.
In summer I recommend a little thicker full synthetic oil like 20/50
We check the level with the bike balanced on both wheels and fill to the center of the lines
with the dipstick in straight but not screwed in.
Here is the important and unique part about these horizontal engines:
Copied from a GoldWing forum.
If you are parking it on the side stand before you shut the engine off then oil is pooling up behind the two left side pistons and being hot oil, it can seep past any ring gaps in short order and next start up ....
.... poof .... out comes big clouds of blue smoke out both pipes as the exhaust from both sides are mixed in the middle chamber portion of the muffler assy.
Mine did it too when I got it in 1995 and it was embarrassing, more so when riding with my HD mounted buddy.... then one day as I thought about it, I figured out what was happening. Bike only had 26K when I got it, sometimes it smoked after start up after just an hour parked at a resturant maybe.
It's a horizontal opposed engine. Like any engine, oil is splashing around all over the crankcase and is constantly washing the cylinder walls below / behind the pistons. Most engines will naturally drain at shut down, but if you prop a horizontally opposed engine over on one side before it drains, low side pistons don't "drain".
When you are getting ready to shut it down, kill it while still holding it up between your legs before putting a side stand down, then after shut down, ease it a hair to the right and take the weight with your right leg and use the left leg to kick the side stand down, then ease her over left onto the side stand.
This way, the hot oil is first drained out of the left side cylinders from behind the pistons (hot oil will move fast) and into crankcase and then as you ease over to theleft side and side stand, the hot oil in the right two will likewise drain into the crankcase.
After dismounting, at some point, I usually pull her onto center stand if parking for longer periods like in the basement. On a ride, temporary parking, side stand is all I use, but I always shut down first before anything else. Mine never smokes since changing that habit.
We have proudly served and satisfied customers from Rancho Mirage, Palm Springs, Palm Desert, Indian Wells, La Quinta, Cathedral City and Indio to San Diego and and as far away as the Los Angeles area.