Metric vs Imperial Fuel Hose

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Samuel Seidel

Pre-takeoff checklist
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The fuel lines in my plane need to be replaced and I’ve been told they’re metric sized. Will I have any trouble going to an auto parts store and getting replacement line? Pretty sure they don’t stock hose in metric sizes but unsure how far off the hose size will be.
 
What engine? If you can’t find the appropriate metric fuel line (seems like with Euro and Asian auto engines quite common that wouldn’t be an issue) they do make AN to metric adapter fittings. Summit Racing, for example, carries them. Another suggestion is to contact Tom at https://www.tsflightlines.com. He’s awesome and if he can’t build you a line I’m confident that he’ll give you great advice on how best to proceed.
 
It’s an Evektor Sportstar with a Rotax 912, I replaced the fuel lines inside the cabin with the closest imperial equivalent and they fit real nice over the barbed fittings. The imperial hose has a slightly bigger inner diameter but was just as big as a pain to pull off the barbed fitting as the original hose. Secured with a mix of the original Cobra screwless clips (not all survived) and fuel injection clamps from the auto parts store.

The hose to the left tank was so bad that when I kinked it fuel came out from the cracks.
Right tank line was still in good condition.

The POH says to use the left tank as originally there was a fuel return line to the left tank and not the right.

However, someone previously removed the fuel return line to the engine, but the second line from the left wing still exists and ends without being capped near the firewall above my leg. o_O

I capped it and all is well.
 
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Samuel Seidel said:
It’s an Evektor Sportstar with a Rotax 912,
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Have you tried contacting Evektor technical support to get a specification number for the fuel hose? With a spec number you might be able to find an alternate hose.
 
Check out the rotax-owner.com site. On there, the consensus seems to be to use Gates Barricade carburetor lines. Fuel injection lines are too stiff.

I thought sure I had added some lines on my 912ULS on my gyro but I don't see where I did. My lines are Gates 3225 7mm from the factory (in Italy). Trying to get properly sized barbs to install my fuel flow was a challenge: I ended up using a 5/16" hose barb because 1/4" was too small, even though 7mm (0.2755") is closer to 1/4" (0.25") than to 5/16" (0.3125"). In any case, it may be best to try a small piece of 1/4" and 5/16" to see which fits yours best, then buy that in Gates Barricade. But I'm pretty sure it'll end up being the 5/16".

Hope that helps.
 
Let'sgoflying! said:
Can I ask the age and type of hose this was?
Always interested in actual life limits of various parts.
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2007 so about 14 years.


Llewtrah381 said:
Check out the rotax-owner.com site. On there, the consensus seems to be to use Gates Barricade carburetor lines. Fuel injection lines are too stiff.

I thought sure I had added some lines on my 912ULS on my gyro but I don't see where I did. My lines are Gates 3225 7mm from the factory (in Italy). Trying to get properly sized barbs to install my fuel flow was a challenge: I ended up using a 5/16" hose barb because 1/4" was too small, even though 7mm (0.2755") is closer to 1/4" (0.25") than to 5/16" (0.3125"). In any case, it may be best to try a small piece of 1/4" and 5/16" to see which fits yours best, then buy that in Gates Barricade. But I'm pretty sure it'll end up being the 5/16".

Hope that helps.
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1/4 was the perfect size and what I ended up using. Like you I did my research and was going to buy gates barricade hose but when I was comparing the hoses at the auto parts store I didn’t notice that the 1/4 lines were Gates Safety Stripe II. Looked it up and it’s good for ethanol up to 70% and leaded fuels. So that’s what I ended up using.
 
Llewtrah381 said:
7mm (0.2755") is closer to 1/4" (0.25") than to 5/16" (0.3125"). In any case, it may be best to try a small piece of 1/4" and 5/16" to see which fits yours best
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FWIW, 5/16" (.3125) is almost exactly 8mm (.315)

I see McMaster has Buna-N hose in 6, 8, and 1mm, as well as 3/16, 1/4, 5/16, and 3/8. Though when I replaced the hoses in my Fisher 404 I used marine hose, which has a better rating than automotive hose. My Hatz has proper Aeroquip-type hoses.
 
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