/5 leaky fuel line

[9842]

Hi
Went for a nice early morning ride this morning and had to return home with what I thought was a leaky carb. Noticed drip on startup and thought it will go away as I ride. You know these old 5’s, maybe the leak will shake itself and be ok, or it will settle in and be ok. The leak was bad so I had to turn back after about an 1/8th of a mile. When I got home and knelt down next to the bike I noticed it was not the carbs leaking, it was the fuel lines. They were soaking wet on both sides of the bike. I shut off the gas, and pulled float bowls and drained gas. I pinched and twisted the lines and they felt squishy and were loose at the connections. I waited an hour and everything dried out. Then I turned petcocks on and noticed the lines slowly getting wet with gas starting at the joints.

I had new lines and filters put on in 2019, so 4 years ago.
No leaks in 4 years untill now
Topped off tank recently with shell 93. No treatment or stable products.
Put race gas in over the winter. Bike stored in Maine.
Lines are braided, don’t know make of lines.

What do you think?
What new braided line do I use that won’t leak?
Thanks
Brian

 

[20774]

Brian -

This has been reported before...seems that over time the original braided lines will eventually crack and then seep gas. I don't think it's a universal problem...I have used only the braided lines on my bikes for years...I don't change them that often, typically only when I'm doing some sort of major overhaul. People do resort automobile 1/4" fuel line that is for regular gas engines, not fuel injected ones. But you can get the OEM braided lines from dealers such as MaxBMW. I believe older VWs also used this type of fuel line.

 

[9842]

Napa 1/4 inch rubber fuel line

Hi
Did a little reading and rubber line is preferred over braided line. I’m off to Napa to get 3ft of 1/4 inch gas line. Of course it’s sunday on a holiday weekend. So my quick fix might be the new better way. I’m reading that the German braided line will not hold up and will crack in 4-5 years. That’s where I’m at, 4 years and have to replace already. Hope I’m doing the right thing.
Brian

 

[20774]

Brian -

You're doing the right thing if it works for you!! I prefer the braided line and haven't really had any issues. I don't know why things have worked for me. My bike is mostly garaged so not much opportunity for ozone breakdown. When I finish a ride, I usually turn off the petcocks a block or so from my house, so any fuel in the lines might be burned and not sit in the lines during the downtime. And keeping petcocks off when not in use helps stop fuel from leaking through and sitting in the lines.

It's been a while since I measured things...I can't remember if the original line is 6mm or 7mm ID. The 1/4" fuel line is around 6.3mm ID. So either your new line will fit loose or fit tight. Might want to consider some silicone on the fuel petcock stub to help it on and off. I've also read where some will put a largish fender washer on the stub before the hose which then gives you something to pull with when trying to get it off next time.

The fuel line has to cross over through the air cleaner. Not sure how the OD of the 1/4" hose will work there.

 

[gregfeeler]

Hi
Went for a nice early morning ride this morning and had to return home with what I thought was a leaky carb. Noticed drip on startup and thought it will go away as I ride. You know these old 5’s, maybe the leak will shake itself and be ok, or it will settle in and be ok. The leak was bad so I had to turn back after about an 1/8th of a mile. When I got home and knelt down next to the bike I noticed it was not the carbs leaking, it was the fuel lines. They were soaking wet on both sides of the bike. I shut off the gas, and pulled float bowls and drained gas. I pinched and twisted the lines and they felt squishy and were loose at the connections. I waited an hour and everything dried out. Then I turned petcocks on and noticed the lines slowly getting wet with gas starting at the joints.

I had new lines and filters put on in 2019, so 4 years ago.
No leaks in 4 years untill now
Topped off tank recently with shell 93. No treatment or stable products.
Put race gas in over the winter. Bike stored in Maine.
Lines are braided, don’t know make of lines.

What do you think?
What new braided line do I use that won’t leak?
Thanks
Brian

Proper fuel line shouldn't be leaking as you describe after only 4 years. To the the exact BMW /5 fuel line, find someone who works on air cooled VW's and buy four feet of line from them. It is rubber line but with a cloth "braiding" on the outside for strength.