I apologize if this issue has allready been addressed. if it has please refer me to the topic...otherwise, here's the prob....
I'm running a stock Mikuni 38mm carb on my 500r and the bike runs great, so needle setting, main jet, needle jet, all seem to be in order. I have good spark. Motor is brand new, lots and lots of compression. The float level is set correct. the needle and seat are perfect. The floats actullay float when put in a container of gas so I know they are not saturated(water logged so to speak). I've messed with the air screw and that doesnt seem to help. Once the engine is started, it will idle all day long, it doesnt stumble off idle when given throttle. What happens is as i kickstart the motor, fuel starts to drip out of the overflow tubes on the carb, the spark plug gets soaked, and zilla goes night night. Is it a pilot jet problem(too big maybe..its a #20, smaller than the stock #22.5) or is it just that this carb sucks and i need a Kehin? My motor is at 535CC. Is the extra displacement making extra pilot circuit suckage? Thanks for any help anyone can give.
HAZ

 

your carb may just be wore out like mine, mine has a bunch of play in the slide because it is wore so bad, i got a kiehen but not on yet.

 

You sure about your float height? and are you sure the needle and seat are really sealing?
Sounds like an overflow to me, definitely not jetting related (Not since the bike runs great... when it runs)

 

mine drips gas too, but it does it even if i dont kick it. like if i leave the gas on accidentaly, and come back in the morning, she would have been drippin all night, as long as i turn the gas off when im done riding its fine. i just remember to shut gas off

 

My slide does show a bit of wear come to think of it. So it may be time to deep-six the Mikuni. The float height is set to stock height (.440 thousanths from the reference line shown in the manual) . I have also tried setting it such that the floats will close the needle sooner, lowering the level in the bowl. (no effect) . There is zero wear on the needle and seat. I've taken them both out and tested them for leakage(in the best way I can) and they appear to seal. [img]i/expressions/face-icon-small-sad.gif[/img]
Duneaddict: how do u test the needle and seat to be sure?

 

20 pilot jet?
if you run a pwk 39,you might at least have a 60-65 pilot in it,
20 seem a lot too lean,with a big bore it will run leaner on bottom end.

 

I check my float level once/season... usually I can tell if my needle/seat are leaking from spillage from the overflow tubes. I actually test by hooking up the fuel supply line, leaving the float bowl off, and manually closing the brass arm a time or two.

I've seen brand new needle/seats dribble with no visible damage.

Just a thought.

 

that's a great suggestion Duneaddict, I'll try that. If it does dribble, do you simply get another needle and seat set, or is there a way to make them seat together better. If its a new set, do you return em for another set?

 

I've found it depends on the manufacturer of the part... some needles use a rubber tip, while others don't.
I haven't had any/much luck improving a seal on one that leaks... better to just replace.
If it's a new unit.... perhaps you'll get some cooperation on a replacement?

Good luck