Petcock Question

[veloce430]

Why does the V need the vaccum actuated petcock?  It seems that someone had an earlier post about using a Yamaha dirt bike petcock with no problems (on an '82) I would think a normal  off/on/res petcock would work. Also, why is the return line needed on the '83?  What happens if they are blocked off?

[louthepou]

My memory (not the greatest) tells me:

Vacuum because gravity alone isn't enough to bring fuel to the carb once the fuel level in the tank is low.

Return line in 83 because some 82 carbs in some places had trouble with boiling gasoline. Return line and insulating lining on tank helped cure the problem.

Lou

[gbranche]

Vacuum because gravity alone isn't enough to bring fuel to the carb once the fuel level in the tank is low.

I think that's the reason for the vacuum operated fuel pump, which is a different beast altogether.

The vacuum operated petcock was developed to keep the morons from killing themselves, when they walk out to their garage with their lit cigarette in their mouth, only to find the floor covered in gasoline, from the carb overflow tubes, which drained the float bowls that overfilled, because the floats stuck, which wouldn't have been a problem if they had remembered to turn the petcock OFF at the end of their last ride in the first place.

The vacuum operated petcock is just one less thing for the operator to have to worry about.

Greg

[veloce430]

Isn't the fuel pump there for the purpose of getting fuel to the carbs when the fuel level is low?  I thought that the vaccum actuated petcocks were done so that you didn't have to turn off the fuel when you stopped.  I believe the other Vision owner (listing his bike on Ebay) used a petcock from a IT 465 mid eighties vintage, with no problem.  Has anyone tried using a small electric fuel pump in lieu of the Yamaha diaphram mechanical pump?  If so any idea of what the maximum fuel pressure you can get away with?  I picked up a Weber IDF on Ebay a couple weeks ago and think that will be my next Vision project.. Maybe Blake would like to tackle some manifolds?  HA!