The Hondas have a vacuum driven fuel pump. It uses vacuum pulses from the intake manifold to activate the diaphragm to pump the fuel.
So extended run tanks work fine on the Honda, because you can just plumb the fuel feed from the external tank into the fuel cap, and the fuel pump will create a vacuum in the fuel tank, which will pull in fuel from the external tank.
A generator without a fuel pump, or without a sealed fuel tank/cap which allows vacuum to be created, won't suck in fuel from the external tank, so you have rig a gravity feed for that.
I don't recall offhand if the Yamahas have a fuel pump, but a vacuum impulse fuel pump can be fitted to any little thumper engine if you can find a place to tap vacuum on the intake manifold.
With propane of course, it's irrelevant since the fuel is under pressure to begin with.
Last edited by dwh; 08-14-2012 at 04:29 AM.
Current: 76 E-250, bubble-top, self-contained|couple of old Yamaha enduros
Previous wheelers: 41 Willys|78 FJ40|78 Bronco|84 Bronco|74 Ramcharger|78 Ramcharger|79 D150 PowerWagon|77 D100|79 D400 dually, converted to 4WD, utility bed, 10' Lance|75 Westy|69 Scout, RHD|bunch of others|bunch of bikes|couple of boats|couple of motorhomes|blah blah|so what|not my idea|just doin' what I'm told|wank wank|this space for rent|candy is dandy|but liquor is quicker