TOPIC:

On the bike or no the bench this float valve will not completely shut off fuel. Fuel seeps past it until the carburetor overflows. Is this to be expected as compaired to rubber tipped valves?

Bit sparse on info. Aftermarket or oem mikuni?, new or worn?
Original mikuni all metal ones that are not worn are pretty good. That said, they were never designed as an on off switch. That is the function of the fuel tap, gravity or vacuum. 
 

Which bike are you working on? Would help to know if it's the KE or KZ... or?

 

You can't expect the needle/seat to seal 100%.  Such as leaving the petcock on Prime, and parking the bike.  There will be some dribbling.  They should seal well enough, though, to measure fuel level, and have it be stable.  And there should be no visible change of level after 15 minutes or so.  

Warren3200gt wrote:

Bit sparse on info. Aftermarket or oem mikuni?, new or worn?
Original mikuni all metal ones that are not worn are pretty good. That said, they were never designed as an on off switch. That is the function of the fuel tap, gravity or vacuum. 

 

This is the Mikuni carb from my ke100. Most likely the origional. 4000 miles on the bike. Under magnification it does not look worn.
With the carb on the bench attached to a fuel bottle, it leaks a drop every 10 seconds. If this is normal, I woun't get a new one. From Partzalla it would be over $60. and may do the same thing.

One drop every 10 seconds is no good.

Is the seat clean?  A Q-tip with brass polish, spun by a drill motor, helps polish the seat.  

If that doesn't work, get a new float valve.  Check Keyser brand.  They are the next step closer to OEM Mikuni.

They should not leak at all even if you forget turn off fuel petcock. Check the float needle tip .If it has any sign of wear like a dimple ring replace them. Then check the float seats . If the float themselfes  is not airtight they get filled with fuel and dont shut off the fuel as they suposed to.
Put them i a jar with water and look for airbubbles.After the watertest you can weigh them on a microscale and check if one is heavier.

One more thing that can make the carb leak is worn thang.If it has a deep dipmle from the floatneedle it can make the float stick.You can file that down .se pick below
 

Rolf1976_KZ900 wrote:

One more thing that can make the carb leak is worn thang.If it has a deep dipmle from the floatneedle it can make the float stick.You can file that down .se pick below
 
 

After some lapping of the needle into the seat, It has stopped leaking. I'll look for that dimple next time I have the carb apart.