Started my 1997 carbed Road King today to go for a ride. Let it run for a couple of minutes as usual as I always do. Got my helmet and walked over to the bike and saw foamy oil dripping on the ground under the primary. Shut the bike off and on further inspection, I noticed that it was coming out of the what looks like a breather hose that attaches to the top of the tranny then goes up and then loops back down behind the primary. It definitely smells like gear oil.

Bought this bike this past April and this has never happened. Any clues?
No gear oil has been added or changed since I bought the bike. The bike only warmed up for 2 minutes max. I have let it warm up more than that many times without this problem.

 

Too much oil in it?

 

I recommend that you change your transmission oil, especially if you have not touched it since you bought it. Might be overfilled. You have no idea what fluid was put in it. I would do all oil changes if I bought a used bike, just to be 100% sure.

Overfilling it is likely the issue in your case.

 

So how exactly does excess transmission fluid travel up the vent hose while the bike is idling? Transmission fluid doesn't heat up like motor oil while idling.

I had a similar issue when I over filled the transmission fluid but it would vent out after longer rides.

I ended up putting a balloon over the end of the vent tube and secured with a hose clamp to verify it was coming out of the vent tube.

 

Figured out the problem. The driveway leading into my barn is on a pretty good uphill incline. Typically when I back my bikes out I roll them over to the side driveway extension which is fairly level. I rolled the bike to that spot today and fired up the bike. Let it run about 5 minutes and no more gear oil out the tranny breather.

Well, yesterday, due to the fact that there were a lot of vehicles in the driveway, I had no other choice but to park the bike on the incline when showing it. I can't park it aiming into the barn as it will just slide backwards so I parked it parallel to the barn. This cause the left side of the bike to be leaning much more than normal.

After running it on the level area with no oil problem, I decided to park like I did yesterday. Sure enough, after a minute or so, some gear oil staring coming out. Brought it back to the level area and no oil.

The problem was the bike bike leaning over way too far to the left on the incline. I stood the bike up and checked the gear oil level and it was below the full mark so I know there isn't too much oil in the tranny.