Advice on replacing a fuel line

I have a 1979 Kreidler MP-19 and I'm replacing the tubing that runs from the gas tank to the engine. Do I have to worry about getting air in the engine when I put a new tube on? I'm worried that if I just put the tubing on it will trap air inside and when gas runs through it might force air into the engine. Anyone have any advice?

Re: Advice on replacing a fuel line

Air in the fuel line will simply be vented away when it reaches the carb's float bowl. The carburetor is not an air-tight closed system.

There is always quite a bit of air in the float bowl above the pool of liquid fuel. The engine draws only fuel from the bottom of this pool of liquid.

Fresh fuel streams into the bowl through the float needle valve. The reason fuel can flow into the carb is that the bowl is vented. If it weren't vented no fuel could go in or out.

So, any air bubbles that flow from the tube into the carb will just add to the air that's already in there and, since the bowl must be vented to the atmosphere, air bubbles in the line will not matter.

Re: Advice on replacing a fuel line

I've tried vinyl tubing but it goes yellow and becomes brittle quickly. Now I use black rubber looking tubing specifically for fuel, and it seems to last. It was nice to see the fuel going through the fuel line but maybe it's not so useful.

Re: Advice on replacing a fuel line

maybe you can find some larger diameter Tygon fuel tube at a local RC Hobby shop. It's a transparent yellow and you can see through it.

the stuff is used on all sorts of model cars and aircraft .. impervious to nitromethane, gasoline, alcohol, etc ..

I needed a couple feet of 1/8 ID for this Fuel Tank Guage after vinyl and polyethylene tubing and everything else i tried failed.

Found it easily, 50 cents a foot if i recall.. it might be stocked in larger sizes.

Re: Advice on replacing a fuel line

I got 3/16" line clear blue stuff from moped junkyard real cheap by the foot.Jim

Re: Advice on replacing a fuel line

Chris at Mopedwarehouse.com has awesome clear fuel line for $1.00 a foot.. just be sure to tell him what kind of ped it is cause it comes in a couple of sizes!

My friend Twilight has that cool blue kind.. it's pretty psychedelic looking :)

Re: Advice on replacing a fuel line

yeah I was going to run some along the bottom of the ped with blue LEDs at each end, but blue lights on a civy. vehicle and the law don't get along.Jim.,

Re: Advice on replacing a fuel line

joew, nice fuel tank gauge and thanks for the tip on tygon fuel tubing. I just calculate my average kpl/mpg, know the volume size of my tank and calculate the number of kms I can do, then write down the last time I tanked up. When I reach a certain number of kms I tank up. So far I haven't run out of gas. The fuel gauge is much more slick.

Re: Advice on replacing a fuel line

That thread is kinda long but it outlines everything i tried and did.. After a year it's still doing fine and it's on the top of my list of "nice things to have". I havent thought of any improvements that would make me want to change it.

Luckily the PA50's tank has a raised sheet metal bead that protects the gauge tubing and it can be mounted right on the front.. easy to see. But my guess there's a spot for one on any tank.

Re: Advice on replacing a fuel line

Brian Mikami /

These guys have the good fuel line in all kinds of clear colors...I'm getting green. :)

Some of the RC fuel lines are not made for gas...only the nitro.

http://www.74moto.com/eshopprod_cat_776-5990-5996-0-0_product_61832_keyword_helix+AND+fuel+AND+line.HELIX174_RACING_COLORED_FUE.htm

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