While doing the tuning rides on the NC30, I’d noticed a faint smell of gasoline from the seat area. While there shouldn’t really be a way for fuel to get out of the system, that’s where the fuel pump housing is located, so I figured the smell was making its way out somewhere. There was no visible gasoline anywhere.

Eventually I decided to take the seat off to check it out, and it was good that I did. When I pulled the Ballistic battery out, it looked like this:

The battery after being exposed to gasoline. The mottled pattern is from the texture of the foam that holds it in place.

The bottom of the battery had a consistency somewhat like chewing gum, and smelled of gasoline!

It turns out there is a small, almost imperceptible, leak in the fuel pump housing after all. It was small enough that there was no noticeable gasoline leaking out, but apparently enough that it eventually saturated the foam around the battery and partially dissolved the plastic battery body.

Now that I knew there was a leak somewhere, I did some persistent checking and eventually noticed a faint sheen covering the aluminum pump housing right in the corner where the weld had leaked before. It was so little that I could not see it on a piece of tissue after wiping the area, but the paper did smell like gas and after a little while, the sheen returned.

I think what happened is this: the tank has a check valve that lets air in but not out. This avoids pulling a vacuum as fuel is used up, but avoids letting the gasoline evaporate into the environment. After riding for a while, the NC30 gets very warm, including the frame and, eventually, also the fuel. This will pressurize the tank, since the expanding air has nowhere to go, so I suspect this increased pressure when warm pushed enough gas through the pinhole to be significant.

I had leak-checked the housing after welding it, but there must have been some porosity or something that eventually let go under pressure, because, when I put the whole thing under water again now and blew into the inlet hose, a small stream of bubbles came out of the inside corner weld… Oh well, I guess I’ll have to pull out the welder and see if I can fix it.

Also, does anyone else think it seems sort of sketchy to make a motorcycle battery out of plastic that apparently has no resistance to gasoline whatsoever? In contrast, the plastic battery box that the whole thing sits in, and even the foam holder, were totally unaffected by the gasoline. It doesn’t seem out of the question to think that something on a motorcycle would sometimes come into contact with fuel.