I might be going off topic again. But as the OP thinks he might be having tank issues I'll risk the rathe of the moderators. Actually I'd like to thank then for their guidance through that VERY subjective "topic rule". (ref. Each forum has a different topic, so what is appropriate in one forum or thread may not be appropriate in another).
Here goes:


As I have stated earlier it is estimated that 80% of engine troubles can be traced to tank and fuel line issue. The fuel tank should be placed so that the tank center line is placed vertically within 5 mm of the spray bar when the aircraft is in its flight attitude. The fuel tank needs to be protected from vibration by loose fitting foam in the fuel tank compartment or use some form of bladder (bubbleless) tank.

Now what often trips up the sport pilot is the fuel line and its hardware. In the old days we tended to use brass or aluminum tubing to carry the fuel through the tank stopper or to splice the fuel tubing. These metal tubes often had a sharp burr that would cut very small pin holes into the silicon lines. Even if there was no burr the fact that the metal line ended with little or no radius would often result in cuts to the fuel lines. To solve these issues one should use polypropylene tubing for glow fueled set ups. Polypropylene can be flame polished to remove any burrs, it can also be formed ,by just keeping it in the heat a little longer, into a radiused retention barb. This keeps the fuel line on securely even with most pressured fuel systems, and eliminates the source of most cuts in the fuel lines. I hope the attached photos help make this clear.

Some have had issues with the term flame polishing. It is a term that has been used long before plastics came into the vernacular. It refers to any smoothing of a surface with heat. I think it was first used as it applied to glass work.

I get most of my thick walled Polypropylene tubing from left over Dubro Engine Control Cable P/N 165.

Please be sure the twist the tubing between ones fingers. (Note the use of an electric stove is actually preferred). The third picture has the retention barb outlined in yellow as a visual aid.

Friends don't let friends fly nickel,

Konrad