Topic: Carbs leaking

[Chuck]

I have a 9200 mile '73 CB500K2 with the original Keihin carbs. I have been unable to correct an overflowing bowl problem on all four carbs. The po installed new float needles and seats.
I have replaced the floats and lowered them 3-4 mm below factory spec.
Here is the puzzler; this occurs after the bike has sat for a few weeks (gas off) only. If ridden; leaking stops eventually. If ridden again in a few days, no leaking. My next step, unless advised otherwise, is to measure level with drilled out bowl screw/clear tube method.

Thanks for suggestions.

[flybox1]

Because you have aftermarket float valves, and new floats,  you need to perform the clear tube ttest to ensure you have the correct bowl fuel level.  3mm below the top edge of the bowl is the goal.  Adjust your floats as needed. You cant guess at this.  Test. Adjust. Repeat till correct.  It will also stop your leaking carb issue. There are many threads about performing the clear tube test.  Use the search function above.

[chewbacca5000]

How is the inside of your tank?  Alot of the overflow problems I run into are from crud in the tank not the carbs themselves.

[Jon_murph]

Harline cracks in overflow tubes (clean with scotchbrite, plug one end and suck on other)

Or a hung up float could be another (po of my bike made his own gasket and kept hanging up one of the floats)

I second the clear tube test i learned how finicy these bikes are with float height the hard way

[Phinn]

How is the inside of your tank?  Alot of the overflow problems I run into are from crud in the tank not the carbs themselves.

+1. The only advantage my (otherwise inferior) 78 carbs have over the earlier models is the viton-tipped float valves. The older metal-to-metal valve seal must be difficult to maintain, especially with aftermarket components. But even with high-quality flexible tips on new float valves in my PD42Bs, I couldn't stop the leaks. I finally traced the leak to crud from the tank. I imagine that tank crud would be an even greater issue in the earlier models.

[Deltarider]

Verify floats swing easily. Sometimes the floatpins (axes?) where the floats swing on, need to be polished lightly. A bit of toothpaste maybe or cigar ash.