Blasted Needle valves WILL NOT SEAL

[79XS11F]

I'm trying to bench test my carbs before putting them back on the bike. I was having some flooding past the needle valves so I replaced all 4 with Yamaha OEM needle valves with needles. I also replaced the fuel "T"s and for the bench test I put the carbs upside down on the Bench and hook up a vac pump to the fuel supply hose. I can not get ether pair to hold a vacuum. 3 years ago when I restored this bike I had not problem getting the needle valves to hold a vacuum on the same test method so I am sure they are going to leak.
I'm wondering if I should perhaps use a set of the rubber tipped needles I have here. Will they fit if I remove the little wire brackets that are used to hold those needles to the floats?
Rob

[TopCatGr58]

Hey Rob,

The rubber/viton tipped valves will not work in the metal valve style seats, they are too big and will get stuck. That's why folks have to get the valve seats from the XV920 or such that screw in to the older carbs and have enough room for the wider vition tipped valves.

Just a suggestion, you said you replaced the "T" connectors, but have you tried putting your finger/tape over the valve seat opening and then applied the vacuum pump to ensure that you can get a vacuum without the needle? You might have a leak at the "T" connector even with NEW ones?? JAT?

T.C.

[79XS11F]

Ya, that was the first thing I did which is what resulted in the new "T"s but I have not had the bowls off again since then. So I guess I will have to do a vac test with the needle valves removed then with the valves in place to check their seal and then with the needles again.
Rob

[skids]

I have seen some stick float pivots before...

[Toolmaker Tim]

Float valves

Get the XV 920 float valves, no more problems. Best money I ever spent on my carbs.

[81xsproject]

Once you make the switch, you will never go back to all brass. Especially considering that once you have the seats, you will only ever have to buy just the needles.

[79XS11F]

Get the XV 920 float valves, no more problems. Best money I ever spent on my carbs.

Are they going to thread right into place on these 79 carbs?
Rob