Carb flooding because of sticking float needles coated with film of dissolved fuel line from alcohol

I had a carb flooding problem that took a long time for me to figure out. I couldn't solve it and was about to switch carbs. I Finally put it under a mircoscope and found out that alk in fuel eats at the clear fuel line over time and a tiny bit of dissolved fuel line sticks to the sides of the float needle. There was a very thin black film on the side ribs of the float needle. When the petcock is turned off and the carb dries out after a few days - the goo hardens and glues one side (rib) of the needle to the float needle bore and the carb floods when you turn on the petcock. I verified this by removing the bowls and saw that the floats/needles were stuck after drying overnight. Some brands of carbs may have enough float leverage to prevent the needles from sticking but it happened to my little PWKs after years of use. The solution was to clean the thin dark goo from the needles and switch to black viton fuel line which does not disolve. I couldn't find any suitable clear fuel line that was ethanol laced gas proof. You have to look at a piece of old clear fuel line under a microscope to see if the inside is getting soft or turning fuzzy (dissolving ever so slowly on a microspopic level). I haven't heard of this happening to the Keihin CRs or FCRs but I would never trust any fuel line not rated for gas laced with alk. Use black viton - available from Mcmaster Carr

This is all I will use. Stays pliable. Pulls easily off barb fittings. No clamps needed. No leaks.

Any modern automotive fuel line should be Ethanol fuel rated. I have only seen these in black solid. The Tygon or other vinyl, clear type lines are more than likely not Ethanol rated.

I don't use any Ethanol fuels in my bikes and always top premium fuel 98 octane and automotive fuel lines (black).

Hmmm...I've been using "normal" gas from whatever gas station since I bought my current Commando in '06. I have never tried to find non-ethanol gas. In '07 I replaced the original 'clear' fuel line assembly with a new clear fuel line assembly from Old Britts. I have never had any sticking float needles with the (Amal) carbs.

Maybe there are (were) different formulations used in the clear fuel tubing that might make some versions prone to failure while others were not. Of course there would be no way of knowing that beforehand. I can only say that I haven't had that problem. One would think that the clear fuel tubing would no longer be sold by Norton parts suppliers if it was not suitable for modern fuel - that's a huge lawsuit waiting to happen should a major failure occur. If they are selling it and the clear tubing is not suitable for E 10 or whatever, I would expect suppliers like AN to state that in the item description.

ashman said:

I don't use any Ethanol fuels in my bikes and always top premium fuel 98 octane and automotive fuel lines (black).

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Like you ,easy to find e free in Au ,guess that's why we call it the lucky country Ash

I use soft EFI rated fuel line for push on fittings. Ideally PTFE in a stainless wrap with AN fittings would be the ticket. Not sure I could figure out how to do it at the carburetor fuel feed though. It's plastic hose barb. Besides why fix something that aint broke.... yet.

I open my petcocks every 3 days and shut them off again after a minute to keep fuel in the bowls. I also use a small amount of fuel injector cleaner, octane booster, and Stabil in a 5 gallon jug of fuel. I always top off the tank with that before a ride. Never know when I'll get in the next ride and Stabil helps keep the fuel volatile. The octane booster is for higher compression insurance.

I did let my FCRs dry out when doing a motor build with your parts Jim. No sticky float needle or flooding. Oddly the only time I had an issue with the FCRs is when they were brand spanking new. The right side carburetor flooded as soon as I turned the fuel on. Took them off pulled the float bowls and could not find anything wrong with them. Put them back on and have not had a problem since. Probably just jinxed them saying that.

Many of us are using Tygon fuel line. It’s a clear yellow/green so you can see the gas flow.

Ian James said:

Like you ,easy to find e free in Au ,guess that's why we call it the lucky country Ash

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Not so easy to find in the UK
Even e5 is getting harder to find in my area
It's all E10 now

ILLF8ED said:

Many of us are using Tygon fuel line. It’s a clear yellow/green so you can see the gas flow.

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My problem was with clear Tygon. Maybe your yellowish Tygon is different but I am suspicious. Versilion is another name for Tygon. The only way to be sure is to check the specs to see if its actually rated for gasoline. The only Tygon/Versilion tubing I found that is rated for gasoline has a separate inner liner of another material that is unsatisfactory because the inner liner can separate. After a year of use I noticed that the ID of tygon tubing was getting gummy and could be damaged when removing the tubing from the petcock. With magnification you could see tiny pieces of the tubing ID coming loose inside the tubing. This is a bummer because its convenient to be able to view liquid inside the fuel line.

I missed the word alcohol in the subject line. Sheesh. I have never used alternate fuels, so as usual my comments are irrelevant. It's good to be consistent.

Schwany said:

I missed the word alcohol in the subject line. Sheesh. I have never used alternate fuels, so as usual my comments are irrelevant. It's good to be consistent.

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Your comments are revelant - I should have said "gas with ethanol". I'm talking about pump gasoline - not straight alky.

Tygon F-4040-A is the ethanol resistant version for fuel line. I have been using it for several years with no embrittlement or dissolving with E10 fuel.
That said E10 leaves a residue in the carb bowl that fowls the jets. I have finally started following other Brit bike owners draining the bowls after each ride.

Running proper black ethanol rated line with clear filters is a solution if you like to confirm fuel presence.

I have found that allowing ethanol fuel to dry out in your carb is a recipe for all sorts of problems. Even if fuel lines don't dissolve.

I left my new Premiers for 6 months without draining them and had:

- green powder aĺl through the small passages

- a yellow golden hard film all over the internal carb surfaces

- a corrosion ring all around the main needle. I had to replace them because it did not polished out and you could feel it with a finger nail.

This is using NZ 95 pump gas which is reportedly 5 % ethanol but AA testing has shown a much wider range of ethanol content than that.

Letting the bike run dry after turning the fuel off is a good idea for semi regular bike use.

"Letting the bike run dry after turning the fuel off is a good idea for semi regular bike use."

Or add some StaBil when refueling prior to storage. I've been doing that (E-10 gas) for 10+ years with no issues of any kind re ethanol AND a fiberglass fastback tank. A friend left his Bonneville (E-10 ) over the winter with no treatment at all and the carbs as you described - crusted/clogged, had to be removed and completely cleaned.

MexicoMike said:

"Letting the bike run dry after turning the fuel off is a good idea for semi regular bike use."

Or add some StaBil when refueling prior to storage. I've been doing that (E-10 gas) for 10+ years with no issues of any kind re ethanol AND a fiberglass fastback tank. A friend left his Bonneville (E-10 ) over the winter with no treatment at all and the carbs as you described - crusted/clogged, had to be removed and completely cleaned.

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I have a bottle of StaBil and use it over winter. I had not considered it for every day use. I‘ll give it a try…..Thanks.

ILLF8ED said:

Tygon F-4040-A is the ethanol resistant version for fuel line. I have been using it for several years with no embrittlement or dissolving with E10 fuel.
That said E10 leaves a residue in the carb bowl that fowls the jets. I have finally started following other Brit bike owners draining the bowls after each ride.

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See the warning McmasterCarr gives for Tygon F-4040-A
here's the link:
Read the details at the bottom - "Do not use with ethanol based gasoline". You might see internal degredation after a year or so.

I always turn off my petcocks about 1/2 mile from home and come in popping on one cylinder till it runs dry - maybe good for avoiding carb corrosion but it didn't prevent contamination from deteriorating fuel line.

jseng1 said:

See the warning McmasterCarr gives for Tygon F-4040-A
here's the link:

McMaster-Carr

McMaster-Carr is the complete source for your plant with over 595,000 products. 98% of products ordered ship from stock and deliver same or next day.

www.mcmaster.com

Read the details at the bottom - "Do not use with ethanol based gasoline". You might see internal degredation after a year or so.

I always turn off my petcocks about 1/2 mile from home and come in popping on one cylinder till it runs dry - maybe good for avoiding carb corrosion but it didn't prevent contamination from deteriorating fuel line.

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Well not sure who to believe. Is this another political thing…getting old.

skysp.net site

1/4" Tygon Fuel Line - Not Affected by Ethanol - Sold by the foot.

Tygon is more of a brand than a material type. The clear line is usually a vinyl or PVC material which are not good in UV and likely the least chemical/ fuel proof, ethanol or otherwise. Yellow stuff maybe better, depending on its composition. Since vast majority of modern fuel lines for cars will be solid black, ethanol rated, this is what is the best option IMHO.