Mine leaked opposite of the cold start lever. Just an "O" ring but I
had to buy the complete seal kit ($30) to get one. Be very careful as
it is spring loaded under the cap. Easy but be careful. None of the
parts/seals are labeled - you must match with old one - new one was
colored green in my kit.

By the way, I bought and installed a NAPA low pressure (~6 psi)
"tick-tick" (Solenoid style) fuel pump ($44) because I was losing prime
and installed it between tank fuel line and before filter.
Took power from fuel solenoid so it primed pump when key is on, that is
how I saw the leak. I could not tell when it was running as fuel
appeared all over the bottom of the main pump.

Mike