TOPIC:

I created a stand to hold my carbs on while tuning the float bowl levels. The clear tubing is made from two different diameters of pvc from the hardware store. Size the small tube for the nipple, and the large tube for a snug fit on the small tube. The reason to slide the smaller tube into the big tube is to give more surface area and diameter for the gas to
1: Not crawl up the tube in a capillary action
2: Clearly display the meniscus, the U curve where the liquid resides, again having to do with how the liquid is interacting with the tube. Measure from the flat bottom of the curve.



I have my carbs apart right now, but the two brackets that hold the carbs together reside on the two horizontal sides of the stand. The long lower part holds the bottom rail, and it leans in to the tower where the top bracket grabs it. A few passes at the bandsaw to perfect the level and a couple screws in some scrap wood is all that is needed.

I also marked where the carb bowl interface level is on the outside of the vertical so the tubes can all be compared to the same level and not kink the hoses.

Maybe this time I will mount the gas tank over the carbs at the correct height. I have previously used the ketchup bottle on the stand, but it can get messy. I just wish my tank petcock had an off position. Any suggestions here?

I am on my first engine rebuild ever, just wrapping up the carbs for the hundredth time by finding I needed to replace the old o-rings on the fuel rail. Any comments on this system are appreciated, and on my carb choke plate topic that will be going. Thanks to everyone for the past help. I try to repay the community in any way I can.

If the petcock is vacuum there should be no gas flowing unless it's on prime.
Steve

swest wrote: If the petcock is vacuum there should be no gas flowing unless it's on prime.
Steve

It has a diaphragm inside; On / Pri / Res on the petcock, and I just found it in prime, so maybe my attempt after rebuilding everything (petcock included) had the carbs overflowing because it was in prime. Edit: maybe it is in prime from moving it after gas was pissing out the overflow. So the ON position should be off after removal of the fuel line since it isn't getting any vacuum?

The needles should have still cut off the flow though, right? What is the point of a vacuum petcock, and can/should I replace the petcock with a different model?

You are correct that the float needles should prevent excess flow. Sometimes they do not.
The vacuum petcock is mostly a matter of convenience. With a manual one, the rider must remember to turn it off and on every time the bike is ridden or parked. The PRI position is for refilling the carbs after they have been serviced or after the bike has been parked for several weeks and some of the fuel in the bowls has evaporated. Personally, I like the vacuum petcock for street bikes.