Saturday, June 23, 2012

Motorized Bicycle - Fuel Tank

hand made fuel tank
The motor kit comes with a 2.5L peanut style gas tank.  It doesn't look too bad on a standard bike, but it wouldn't have worked on this frame.  Not only was the styling off, but it would never have fit the top tube of the frame without looking like a metal wart.  I needed another solution.

stock peanut tank

As it turns out, the top tube of the bike frame is hollow and can be used as fuel tank.  There are several videos and forum posts that describe the process.  Basically you disassemble the frame, drill a hole on the top of the tube, plug up some holes inside the tube, epoxy on a fuel cap assembly, and seal the tank.  The result is a really clean and authentic looking tank.  Unfortunately, time and money prevented us from going that route.  Instead, I decided to mount a Moon style tank under the rear seat.  All of the suitable commercial tanks that I could find were way too expensive.  Luckily my friend and fellow Road Lord, Jesse from KNS Customs volunteered to build a tank for the bike.  I gave him the dimensions and he went to work.  A short while later, I had the tank in hand.

To mount the tank I inserted two 1/4"-20 threaded rivets in the seat stay bridge.  Then I bolted on a length of 1" aluminum angle where the rear fender meets the bridge.  A pair of stainless hose clamps secured the tank to the base.

tank mount

With the tank mounted I marked a spot to mount the petcock.  I thought I could just drill and tap the tank for the petcock but the tank wall was too thin to thread and the valve arm of the petcock hit the tank when installed.  So I made an aluminum threaded bung on my lathe.  My friend Steve from the club TIG welded the bung to the tank.  With the fabrication on the tank finished, I smoothed out the welds on my belt sander and blasted the tank to give it a nice brushed look that matched the engine.  I placed a rubber shim between the fender and tank to keep things quiet and protect the paint.  Finally, the tank needs to be vented so I drilled a 1/8" hole in the gas cap.

fuel petcock

The petcock has a fuel filter built in but the screen looked a little course.  So I added a second one in the fuel line just in case.  The hose clamps that came with the kit were crap; they split soon after I installed them.  So I replaced them with adjustable hose clamps.

fuel filter
The finished tank really complements the look of the bike.  The capacity is right around 2.5L, same as the stock tank.  With the way the motor sips fuel, that's enough gas for hours of riding.

No comments:

Post a Comment