I have used Tygon for years, and have never had the stiffness issue. It is true a get a bit hearder, but just a bit, and it will acutally soften again in gas. This is why I store the tanks with a littel fuel in them (keep lines soft). Of course, I always put Stabil in my fueling can all the time. If your line is extremely stiff, I would guess it is a lower grade tygon, or fkae tygon...especially the blue stuff. I use this tygon from McMaster Carr, and I have planes 10 years old that I have never changed lines on:
Fuel and Lubricant Yellow Tygon PVC Tubing
Tygon Formulation: F-4040-A
Very flexible
Soft (Shore A57)
Temperature Range: -35° to 165° F
Use with barbed fittings
Not only will this tubing remain flexible when used with gasoline, heating oils, cutting compounds, and coolants, it also withstands lower temperatures than other fuel and lubricant tubing. Tubing is semi-clear yellow; you can see something is in the line, but the view is limited.
View information about the chemical compatibility of PVC tubing.
ID OD Wall Bend
Radius Max. psi
@ 73° F Available
Lengths, ft. Per Ft.
5/64" 9/64" 1/32" 1/4" 40 10, 25, 50 5552K43 $0.80
3/32" 3/16" 3/64" 1/4" 50 10, 25, 50 5552K22 .72
1/8" 1/4" 1/16" 1/4" 50 10, 25, 50 5552K23 .82
3/16" 5/16" 1/16" 1/2" 35 10, 25, 50 5552K24 1.17
1/4" 3/8" 1/16" 1" 30 5, 10, 25, 50 5552K25 1.49
5/16" 7/16" 1/16" 1 1/4" 25 5, 10, 25, 50 5552K26 1.91
3/8" 1/2" 1/16" 1 3/4" 20 5, 10, 25, 50 5552K27 2.23
3/8" 5/8" 1/8" 1" 35 2, 5, 10, 25, 50 5552K32 4.64
7/16" 9/16" 1/16" 2 1/4" 15 2, 5, 10, 25, 50 5552K33 2.93
1/2" 5/8" 1/16" 2 3/4" 15 2, 5, 10, 25, 50 5552K28 3.02
1/2" 3/4" 1/8" 1 3/4" 30 2, 5, 10, 25, 50 5552K42 5.47
5/8" 7/8" 1/8" 2 1/2" 25 2, 5, 10, 25, 50 5552K31 6.22
3/4" 1" 1/8" 3 1/4" 20 2, 5, 10, 20, 25 5552K29 7.03
For clunk, the best is the Bennelt filtered clunk for smoke. You can use it with fuel, it is heavy (compared to the heavy weight Du-Bro stuff) and it fliters
http://www.bennettbuilt.com/shop/Tan...Gas_Large.html
Jeff