Carb float levels

[Neill C]

Hi there. I've been bench testing my carb after suffering from float bowl overflow leaks. One bowl slightly overflows after about four hours. Float levels are set at 22mm as the book says. Would you consider that overflowing after 4 hours is perfectly OK seeing as you should turn the petcock off if the bike is going to be left on its stand for 4 hours anyway?

[SteveW]

Should not leak no matter how long it’s left.

[Neill C]

Of course. I'd get the fuel that's in the pipe after the petcock on my garage floor every time I park her up otherwise. Thanks.

[Oddjob]

Left on side stand or main stand?

[Nurse Julie]

Have you tried tapping the float bowl to see if its the float valve is leaking? Maybe the spring has had it.

[Neill C]

The carb is on the bench in a vice. I've tapped the bowl but still overflows. I'm beginning to think I'll have to set thr float slightly lower than the specified 22mm

[McCabe-Thiele (Ted)]

I would be thinking it's the float needle & seat.
I'd do what was suggested earlier & try to lap the seat before replacing it assuming the float is all good.

[Oddjob]

Have you replaced the float needle and seat by any chance

[Neill C]

Yes. Could the float just be slightly less buoyant than the others? They are 45 years old after all.

[Oddjob]

It’s most likely the needle and seat, well known for aftermarket needles and seats to be sub standard compared to genuine brass. I’ve seen some where the point on the needle isn’t even central.

[Neill C]

What's the answer there then. Do I keep replacing the valve and seat until I find one that doesn't leak?

[Johnny4428]

Neil try a cotton bud in a drill with a little tooth paste and polish up the valve seat. I’ve been lucky never had a problem with these seating. Careful inspection with magnifier too at tip of valve.😉

[Neill C]

I'm going to try that. Thanks

[Matt_Harrington]

As the carbs are on the bench, try swapping the valve etc over with one that doesn't leak and see if the overflow moves with the valve. Just a thought.

[deltarider]

I'm going to try that. Thanks

A drill is too much and asking for problems.  Do it by hand. It takes very little, maybe one turn.