Float valves

[Black Rarebit]

Hi
Recently overhauled the carbs and managed to get rid of the dreaded stutter. My new problem is fuel seeping into the crank case. I will also occasionally run out of power if maintaining a speed of 100kph which seems to be caused by lack of fuel getting to carbs.

I think I need to replace the float valves, but want to make sure before investing in new ones. Any clues as to what to look for when you have the valves in your hand? How much should the rubber 0 ring stick out from the body. On mine it looks almost the same diameter as the valve body. Can you just replace the o rings?

Checked the float level after 5 mins running and they sat at about 25/26mm. Could this be a major factor in fuel seepage or loss of power?

Which way should I adjust the tang of the floats to get the required height? Sorry people. Lots of questions!!

Thanks in advance for any suggestions.

Cheers

Paul

[QBS]

Fuel in the oil can only happen when at least one of the carbs has a leaky float needle valve AND an inoperative float bowl drainage system.

[Rikugun]

Fuel can leak past the O-rings, not just through a leaky needle/seat. Even a functioning overflow system can be overwhelmed at sufficiently high flow rates. Fuel will find it's way to the carb vents leaking externally and the venturi and leak into the engine. Yes, you can replace just the O-rings. I choose ones that had the seat offer slight resistance when pushed into the carb body and have had no leaks.

Losing power at 60+mph may be an unrelated problem. Could be a lean issue like a clogged main jet? Air box flapper not opening completely?

[musicweb]

Float level to high?

I thought they were set at about 34-36 mm from the face of the carb top, sitting on an angle.....

If they are set at 26mm, you will have overflow.

[Rikugun]

36 mm is what my manual suggests also but that is using a float level gage with the carbs assembled. I'm not sure what method you are using.

If the bendable tab is flush with the metal arms that hold the float halves, that will probably be close enough. I've found this to be the way most Japanese bikes are set from the factory.

Having said that, it's been suggested that the overflow tubes on some Visions were too short resulting in overflow. In those cases it was advised to lower the level a couple of mm. I have no personal experience with this, just something I read somwhere.

[Lucky]

Having said that, it's been suggested that the overflow tubes on some Visions were too short resulting in overflow. In those cases it was advised to lower the level a couple of mm. I have no personal experience with this, just something I read somwhere.

that's  me, i have found half a dozen or so 82 carbs over the years that typicly have the overflow tubes 2 or 3mm low.

i generally set mine at 38-39mm & have no loss of perfomance.

--Lucky

[Walt_M.]

I have long thought the float levels on my '83 were too high from the factory. I didn't adjust them when I did my rebuild and it is darn near impossible to start when warm if I leave it on the sidestand. My 'fix' is leave it on the centerstand.

[Black Rarebit]

Thanks for the feedback guys.

Is the float height specification the same for xz400s as xz550s?

I was following the 550 manual which stated... The fuel level in the clear fuel line(attached to the the front carburetor drain fitting— must be the specified distance (20mm) below the gasket surface of the main body.

Cheers

[The Prophet of Doom]

Is the float height specification the same for xz400s as xz550s?

XZ400 carb spec is
Type: BD34
ID Mark: 14x10
Main Jet:107.5F 110R
Main Air: 1.8
Trottle Valve:120
Pilot Jet:60
Pilot Air:146
Pilot Screw: 3 1/2 +- 1/2
Valve Seat:1.8
Starter Jet: 40
Fuel Level : 21mm +- 1mm
Float Height: 36mm +- 1mm
Idle:1300 +-50 rpm
Idle Vacuum > 150mm Hg
Sync Difference < 10mm Hg
These use the same BD34 carbs as the US 82s

[Black Rarebit]

Thanks again for all your help. I fitted the float valves (with new o rings) from my donor bike and it did the trick. No more leaking fuel and it also seemed to have solved the lack of power issue. Good to go.