Check fuel supply. To determine if fuel starvation is the cause, fill the carb float bowl using a squirt bottle. If it cranks easily and runs for about 10 seconds or less, you can bet that somewhere in your system is a fuel choke point. Check screen plugging in your fuel pump bowl screen. Takes about 2 minutes. Mine plugged twice last week with very fine rust (time to clean the old tank).
Depending on which year and model you have, there is a short (8 inch or so) fuel line starting at the tank needle valve down to the edge of the frame. It appears to be a cloth covered line, but premium gasoline reduces the coating inside the cloth covering the flexible line to what appears to be viscous tar (had to replace mine with a copper compression line today).
If you have an Eectrolock, check grounding of the wire coming from the key switch where it exits the Electrolock at the coil. Hotrodlincoln is dead on about clean connections in a 6 volt system. He gives very good advice.
If you want a 6 volt battery that will crank a 216 all day without dying, try a NAPA Commercial. Mine went through 3 days of cranking before it bit the dust. At 6 amps, it took 2 days to recharge it. They run abut $140 all day long, and I highly recommend them.
Good luck.
Jim
