Motorcycle Repair: Yamaha carb overflow, japanese bikes, gas leaks

Question
I recently bought a 79 Yamaha 1100. Even though I shut the petcocks off after riding, gas leaks through & ends up in the crankcase. The previous owner changed tanks & removed vacuum assembly and ran a gas line from one side of tank petcock to the other side. Do petcocks need new orings or complete rebuild or replace with different type since no vacuum & are sticking carb floats adding to problem?  Bike runs fine without vacuum assembly.

Answer
Hi Don.
 Sticking floats could be adding to the problem, but I think that the problem is really the fact that the fuel line and valve need to be set up correctly.  The fuel vale may even need to be rebuilt, which is most likely.
 Japanese bikes use a vacuum actuated valve and so that system needs to be in place and set up as per the factory setup.

Get everything back to original and test it.  If it still doesn't work right, then rebuild the fuel valve.

Good luck.
FALCON