Proper Fuel Line Size
 

This should be a fairly simple question. I have not be active flying now for about three years and want to get active again. I have three trainer planes and that is all that I have flown. I started out with an OS La 40 engine and then bought two OS Max 46 AX engines and have used them on my trainers. Getting all my stuff out and checking out my planes now, I have noticed something that I am not sure what I knew back when I got into this hobby. I have noticed that the fuel lines that I have are in two sizes. I am not sure what they are called, Large, medium, etc but I do know what the inside diameters measure. One line has a inside that measures 1/16 of an inch and the other measures 2/16 of an inch. Now again, I am not sure to the best of my recognition what size line I started out with when I started in this hobby. What it appears is that I had the larger size line on the engine I just pulled off the other day but when I went to replace it with large size line, it seemed to have a fairly lose fit on the metal tubing coming out of the fuel tank. This didn't make me feel comfortable. When I put the smaller size line on it seemed to have a good tight fit. Also the metal tubing coming out of the fuel tank seems to be the same inside diameter, 1/16, as the 1/16 inside diameter fuel line. The smaller sized line will fit on the engine also. My question is this. Given that I am using the OS Max 46 AX engine, is there any problem using this line? Will I be getting all the fuel that the engine needs. Is there any question that I will not be getting enough fuel that the engine needs?

Thank you in advance for your help.

Poppy2

RE: Proper Fuel Line Size
 

Medium

RE: Proper Fuel Line Size
 

Hi!
You can use many sizes! Doesn't matter what size you use as long as it not slips off from the carb nipple.
1,5-2mm inside diameter is normal for all glow engines no matter size!

RE: Proper Fuel Line Size
 

The brass tube on a DuBro tank measures 3.22mm or just over 1/8 in. The line should be a bit snug but not overly tight. Only time I bother to barb the brass lines is on my YS engines. I do cut about 1/8 inch of fuel line and put it over the main lines then slide it back over the nipples and tank tubes. This just tightens the lines so they don't slide off.

RE: Proper Fuel Line Size
 

Thanks for all the input. I don't know why I never realized that there were different size fuel lines. My concern was focused on aerodynamics, battery charging and engine tuning. Fuel line size just fell through the cracks some how. I will be using the medium silicone tubing, ID 3/32 (2.3mm). Hopfully this information might be helpfu or enlightening to someone else down the road. Thanks again.

Poppy2

RE: Proper Fuel Line Size
 

I checked the owners manual for your engine. It says to use silicone tubing with a O.D.=5 mm and an I.D.=2.5mm.

2.5mm=0.09 in. 3/32=0.09 inch, so the the medium 3/32 ID tubing is what you should use. I learned something too. I never really thought about it before.

Brian

RE: Proper Fuel Line Size
 

Simply match the ID of the fuel line with the ID of the inlet on the carb. Anything larger is a waste.