I got a used plane. I need to replace the fuel line but I’m not sure what size i need. 1/8” or 3/32”. For a gas engine. I was thinking flow master 1/8 but i dont know the difference. I have a GP 123

I use 1/8 inside diameter fuel line on everything

https://www.mcmaster.com/5119k41
Use this and you are done forever.

I would use 1/8" for 50cc and above.

The I.D. of the carburetor fuel inlet is the size you need.

Originally Posted by ERICKUO

The I.D. of the carburetor fuel inlet is the size you need.

And every newer Walbro carb uses the same inlet fitting size regardless of carb size. 1/8" ID line seems best. 3/32" is preferred by some but it can be very difficult to get on fittings. Some chainsaws and lawn equipment use a Viton line size just a tiny bit smaller than 1/8" that seems to work well.

I use 3/32 for under 50cc Normally, the Small Diameter helps with fuel draw a little bit also fits the smaler fittings better.

1/8 for 50cc and upto 200cc+

But Really 1/8 can be used for all. As Trucker said the newer carbs all seasm to be 1/8 as are most new gas fuel tanks regardless of size.