Viton Float Valves for older carbs

[81xsproject]

I discovered a way for folks with older steel/brass needle valve assemblies to get and use Viton tipped ones. Here are some pics of the two different types installed. The only difference that I can see so far, is that the filter screen is attached, they use a metal washer instead of a fiber, and as best as I could measure, the Viton needle sticks up ~.035" higher than the brass assemble. However, this comparison is between an old worn out brass assembly with already crushed fiber washer and a brand new Vitron assembly with uncrushed washer. I imagine this is SOME of the difference. Still very close. Both seats have size 2.0 openings so there shouldn't be any fuel supply issues.






I found these at Z1enterprises and thought I would get some to see if they would work on a pair of '78 carbs I am rebuilding to sell.

They apparently fit:

Float Needle Valve Assembly - Fits Yamaha XJ650G/H/J/K/LH//RJ XJ700N/NC/S/SC XV700L/LC/N/NC/CS/CSC/CT/CTC/SS/SSC XJ750J/K/MK/RH/RJ/RK XV750H/J/K/MK XV920J/K/MK/RH/RJ XV1000L/LC/N/NC XV1100S/SC/T/TC

I will report more as I get everything back together and take the carbs for a spin.

[Ken Talbot]

The way I figure it, .035 is pretty close to 0.9mm That much difference, at 6.0mm from the centreline of the float pivot to the end of the needle, will proportion out to approx 7mm difference out where you measure float height, which is approx 45mm away from the centreline of the float pivot. I'm not saying it won't work, but I'm saying you will need to do some fairly major resetting of the float level. I would be concerned about having to bend the tab so much that it wold no longer be anywhere close to perpendicular to the spring loaded pin. It might make more sense to carefully grind or file that 0.035 off ot the end of the pin.

JAT, YMMV

[81xsproject]

Good news, measuring small distances by eye is extremely inaccurate . Using a much more scientific process than a caliper assisted eyeshot, the difference is much smaller. I installed an old brass assembly, torqued the seat down, installed the float, them measured float height; 1.033". Then I removed the old one, and in the same carb, installed a Vitron setup, and checked the float height; 1.048". So the difference between the two setups is (at the float) .015" or 3.81mm. So, no EXTREME float adjustment required.

[81xsproject]

Since it came up, I thought I would revive this to give the final report on the upgrade. It works very well. I adjusted the floats 1-2mm to get them to spec. Once the carbs were on, I opened both the petcocks and let them sit for about and hour. No dripping. When I took them out for a test ride, I did everything I could to try and starve the carbs by running WOT. I couldn't get them to starve, so I don't think the different valves have any flow problems either.