This is interesting. I ran into a little bit of this last night on my project with the fuel line. I hope it does not become a problem, as it sounds like it has the potential to.
My gravity fed fuel system's line runs right next to one of the engine's throttle mechanisms.
You can check out where I just installed a Predator 420 on a Yerf Dog 3206:
http://www.buggymasters.com/forum/showthread.php?t=5993
Feedback welcome
