Sticky Float Valves

[Mr Helicop]

I am often getting sticky fuel valves, the petrol poors out the carb but is fairly easy to cure by giving the bowl a tap. Is this a common problem? Carbs were stripped and cleaned a thousand miles a ago. Is it related to modern fuels perhaps they are drier if you know what I mean. Anyone using any aditives in the fuel or using the higher octane variety?

[deltarider]

I am often getting sticky fuel valves, the petrol poors out the carb but is fairly easy to cure by giving the bowl a tap.

Hm, this is a bit of a contradiction. Sticky float valves usually cause the float needles to stick up in the valves blocking the fuel supply but... 

Is it related to modern fuels perhaps they are drier if you know what I mean.

... it is certainly also my feeling modern gasolines are less 'lubricous' since lead was phased out. PD carbs on K3 models seem to suffer in particular from this.

Anyone using any aditives in the fuel or using the higher octane variety?

I recommend K3 owners in particular to add just a small 'maintenance dose' of Redex, Seafoam or whatever every tankfill. A small dose of diesel or lamp oil (= kerosene) might do the same.

[JezzaPeach]

I use Sta-Bil and before that had used the tiny carb brushes to give the holes a good clean. I also have got into the habit of turning off the tap a few hundred yards before ending a run to try to leave less fuel in the pipes to evaporate and leave a deposit. No proof it helps.

[Bryanj]

Yup, just done it on a 1500 wing with noisy lifters

[AshimotoK0]

Yup, just done it on a 1500 wing with noisy lifters

Do you remember C-Film in the early 70's Bryan 

[Bryanj]

Nope Ash but remember perseal when it worked!

[AshimotoK0]

Nope Ash but remember perseal when it worked!

You need to Google it Bryan ... probably resulted in a population spike increase 

[Mr Helicop]

Thanks for all the info - looks like adding some seafoam will do no harm so I will try that anyway. Anyone using high octane fuel, any gain in using it?

[deltarider]

I use the cleanest fuel available: V-power, Ultimate and the like. Octane is irrelevant.

[the-chauffeur]

You might also want to take a quick look inside the carbs at the little towers the carb floats attach to. 

It's not unheard of for the metal casting to have degraded over time or just be generally poor quality.  If the float arm catches on rough edges as the float shifts off-centre very slightly, it'll prevent the float assembly from falling cleanly as the fuel level drops. 

[SteveW]

Don’t know if this is relevant but my 66 Lambretta had a similar problem.
The modern fuels cause the float to swell very slightly.
The float is made of an upper and lower part with a seam around the middle. When the float swells the seam rubs on the carb body causing it to stick.

[simonc]

no expert but next time you strip carbs check post tang { not the the height .floatv/v tang ] i have known these to catch on top of posts