Oldjeep wrote: I suppose, but at the point the bike is running then what does it matter? It'll run rich on the cylinder, but it isn't going to hydrolock on a bowl full of fuel. The tank has a vac switch, so the carbs can't be spilling when engine is off.
There are many examples on this and other sites where the vacuum component of the petcock has failed, usually because of a bad diaphragm, and fuel has flowed with the engine shut off. Coupled with sticky floats this problem usually results in a puddle of fuel on the ground under the bike becasue the fuel has flowed out of the carbs through the overflow tubes. Personally, I would not bet my engine that the vacuum petcock will not fail.
Since at TDC the open space above the piston of a 4 cylinder KZ750 is a mere 18.45cc I don't agree with your assertion that it cannot hydrolock on excess fuel. If the petcock is operating properly and in the RUN position it would only do so with the engine running and if the carb float was sticking or very poorly adjusted so excess fuel was flowing into the carb at a pretty good rate. Would that excess fuel equal 18.45cc? Since there are many variables that would affect the amount I have no idea if 18.45cc is or is not within the amount possible.
I'm no carb expert. What I do know is that the engineers that designed the carbs were experts and they put a lot of thought and effort into the development of the carbs. Apparently they felt compelled to put an overflow circuit in the carbs, and I respect their expertise and judgement. Since it cost more to include the overflow than it would have to omit it I seriously doubt that they put that overflow there without having a pretty good reason.
Having said all that it's your bike not mine. So as long as you are comfortable with your modification that's really all that matters. Ed
