I think I am with idodirt on this one!!!

 

I've had the same problem before and it was the "O" rings in the spacer block between the tank and petcock. The leak was so small that it never made the ground, just smelled badly of fuel. Finally it got bad enough that fuel found its way down into the front sprocket area. It dissolved the residual chain lube accumulated in there and made a very funny looking stain on the floor. Not really gas, not really oil. Removed the plastics and that's when I was finally able to see where it was coming from. Two "O" rings and it's been fine ever since.

 

mine wes seeping from the plastic interconnect pipes between the carbs, the O rings in the carb bodies that sealed them had gotten hard allowing fuel to just seep a bit, some slight wetness but gas odor when parked. Unfortuneately you have to disassemble the carb assy to replace the "gold plated" O ring set from Honda ($34.00 per set & two required)!!

 

I had that same problem with mine. Only when I used the fuel pump though. If I ran the line directly to the carbs it was fine. Got the o-rings and replaced them, now it doesn't leak anymore. Have to sync the carbs when you are done though...