Mikuni leaking and other problems

73 850.
I rebuilt the carb about a year ago. Ran great
Let it sit over the pandemic. And now...
When I turn on the petcock it leaks out of the hose from the bottom of the float bowl. After it warmed up this seemed to stop so I thouhgt it fixed itself. A few days later the samething happened.

The other problem. When I turn the throttle the gas seems to get stuck at a high rpm and I have to shut off the bike. It's not the slide - that moves smoothly. I readjusted the air mix and idle mix.

thanks for the help

Are You using ethanol gas , did you drain carb before storing for winter , lube throttle cable , visual check of cable end to end … float bowl may need new gasket , although I have run mine 20+ yrs without and no leaks ever … good luck !

what craig said but ,maybe a lil piece trash in gas got hung un der float needle? do you have inline fuel filters?

Japanese carbs are MUCH less tolerent of dirt like this. Particles that an Amal would just pass straight through without issue will easily cause problems like this.

I’d suggest removing the float bowl and having a good clean in there. And fitting good in-line filters.

As discussed in another post recently, the gauze ‘strainers’ in the tank are fine for Amal’s, but often not for Japanese instruments. And your 50+ year old fuel tank probably ain’t as clean as it was when it was shiny new !

OP, did you use Sta-Bil?

Fast Eddie said:

Japanese carbs are MUCH less tolerent of dirt like this. Particles that an Amal would just pass straight through without issue will easily cause problems like this.

Click to expand...

Agree.

Before you take anything apart try the old standby: tap the perimeter of the float bowel with a small brass hammer gently, if it works enjoy riding, but start by doing orbits of your home to see it it stays fixed.

Next: if the carb is still leaking, and you said you rebuilt it there is a good chance that the fiber washer that seals the float seat isn't compressed enough. Drop the bowel, gently apply more torque to the seat, it's a 9 mm hex, but be very careful here. If you trip the threads your tuition will be a new carb. The right way would be to remove the float arm, needle seat and see if the carb body seat drilling is not fought with casting imperfections, ethanol can erode this surface. If this is the case clean it up and reassemble.

While having the seat out check it for debris/wear. If you need a new seat/needle order a 3.3.

Best

Thanks for the feedback. The bowl only seems to leak when cold. When it's warm - no leaks for the 10 minutes I watched it with the petcock on.
It does have an inline filter and recent fuel line.

I'll drop the bowl and take a look. Might just have to adjust the tang.

The bigger problem right now seems to be that the throttle gets a bit stuck with a 1/8-1/4 twist. Putting a load on the bike seems to take it back down to idle. When I let the clutch out the bike revs down - odd??

Lube cable , or new cable ?

Lubed it. When there's a load on the bike it seems to bring it down sometimes.

You’re not running a fibre glass tank are you ?

No. Steel Roadster tank. Never had this problem. Must be from sitting.

Check that none of your cables are being fouled up by the tank, I've had that a couple of times with symptoms similar to you. Remove the tank and work the cables.