It's a cap. Luckily, I was aware of the fact that some are gauges and can't be twisted.

The scent is greatly diminished today, so I suspect it was just the spillage.

 

can't help with your bike question but:

these are awesome....

http://eagle-mfg.com/catalog/Safety-Cans.aspx


Somehow they're either CARB compliant or just haven't met the ban hammer yet. Free flowing and don't spill.

I stumbled on them after buying a compliant "no-spill" gas can at home depot and spilling gasoline all over the place.

 

UPDATE: Just took it out for a bit. I went about two miles to my usual turnaround point and it was running like a top. Stopped and pushed the choke off. About a mile later it started running at what felt like half power and backfiring like crazy.

What have I done and how did I do it? More importantly, how do I fix it?

 

There seems to be a lot of that going around.....

 

You ran it two miles in this weather with the choke on? It probably was just clearing out all the fuel enough to run after that 3rd mile.

Still, don't see that signature and how would we know what you did to it other than filling it up. And you didn't even tell us you spilled it all over. Why not add that to the first post. Edit is your friend.

If you use the lock on the nozzle on a motorcycle you are going to burn down the gas station.

 

Yep. Live and learn.

But all is well now. I had badly fouled my plugs. I replaced them and it runs great again. I just did a test ride of a few miles.

I also found that the former plugs weren't gapped the same, so I made the new ones match at .040.