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Message started by KennyG on 08/10/15 at 14:15:27

Title: S40 Fuel Line
Post by KennyG on 08/10/15 at 14:15:27

S40 Fuel Line

This posting is "for what it is worth" information and not intended to incite a riot.

I do not think the fuel line for an S40 is 5/16" ID and I know it is not 1/4" ID.

I think the fuel line is 7MM and here is what I base my opinion on:

The brass fitting on our Mikuni carburetor for the fuel line measures .320 OD.

The brass fitting on the factory pet thingy for the fuel line measures .315 OD

The brass fitting on the Raptor petcock for the fuel line measures .320 OD

5/16" converted to a decimal .3125

7MM converted to a decimal is .276

The Suzuki S40 factory fuel line measures .265 ID and .450 OD

My Denton motorcycle dealer who sells Suzuki and also sells at least a dozen other brands of motorcycles, ATVs, water scooters, SlingShots, etc., stocks only one piece of fuel line about 2' long and it is 7.5MM ID. I searched around and the Harley shop had only SAE size fuel line, I tried the John Deere dealer and they had only SAE size fuel line, but thought the Kubota dealer could have metric fuel line since the Kubota products are made in Japan.

Indeed the Kubota dealer does have 7MM fuel line and the part number is 09661-70800-620.
The ID of the Kubota 7MM fuel line measures .274 and the OD measures .480
Although the Kubota fuel line is a little bigger than the Suzuki factory fuel line the Suzuki factory clamps will still fit on the Kubota tubing.

Kenny G

Title: Re: S40 Fuel Line
Post by justin_o_guy2 on 08/10/15 at 16:01:10

If you're tech savvy enough to navigate the search function, this is covered.
I wanna say Dave did a cross section versus area analysis. Small changes in diameter equal big differences in flow. I'd do it for ya, buuut, I dunno how.

Title: Re: S40 Fuel Line
Post by KennyG on 08/10/15 at 17:29:39

Justin,

I did that search and the conclusion was that 5/16" fuel line flows more gas than 1/4" fuel Line.

I do not disagree with that conclusion, but 7MM fuel line is the correct size for the various versions of the Suzuki Big Single, and it fits the carb & petcock correctly.

As a side not the Kubota dealer will make a replacement hydraulic front brake line for $10.00 if the customer supplies the banjos.

Kenny G

Title: Re: S40 Fuel Line
Post by Dave on 08/10/15 at 19:08:05

You are probably right about the 7mm....this parts manual shows the factory line to be (7x12x600) which is 7mm id, 12mm OD, 600mm long I would guess.

http://www.suzukipart.com/oemparts/a/suz/50d33086f8700232d0b3db47/fuel-thingy

In past discussions.....we determined recommended 8mm (0.3149") from the factory- which is very close to 5/16" (0.3125").

http://suzukisavage.com/cgi-bin/YaBB.pl?num=1253212574/14#14

http://suzukisavage.com/cgi-bin/YaBB.pl?num=1399506169/20#20

http://suzukisavage.com/cgi-bin/YaBB.pl?num=1394741711/4#4

The 8mm and 5/16" works fine.....provided you use the spring clamps on the tubing at the fittings.

If you go to an autoparts store you will most likely get fuel line that is pressure rated.....for use with a fuel pump. It has reinforcing fiber inside and the tubing is very thick. It is better to get the correct size fuel hose from a motorcycle dealer or online supplier. Most vacuum hose is not rated for fuel.

And if you feel you need an inline fuel filter - use the 5/16" as that will provide you a larger hole size in the nipples on the filter. The plastic housings are very thick and the hole size in the nipples is reduced significantly and air bubbles can get stuck in the small holes and block fuel flow. (If your bike stops, loses power or runs weird....remove the fuel filter before trying any other trouble shooting).

Title: Re: S40 Fuel Line
Post by digitaltrucker on 08/11/15 at 05:33:54

I use Tygon fuel line, it's a clear yellow line. It's nigh on to indestructible and you can see what's going through it.

Title: Re: S40 Fuel Line
Post by Dave on 08/11/15 at 09:53:58

Tygon is a good fuel line that is resistant to ethanol and I use it on all my yard equipment - but the color clashes with my paint! Tygon can sometimes be purchased in other colors - but it is normally the yellow/green so that it is easily identified as fuel tubing. The only thing Tygon is not too good at is heat resistance, and it should not be run too close to hot things....it is only rated to 165 degrees.

Try to avoid any fuel line that is Nylon.....the ethanol fuel degrades that stuff pretty quickly.

Title: Re: S40 Fuel Line
Post by digitaltrucker on 08/12/15 at 17:47:14

Not all of the black rubber fuel line is very resistant to ethanol either. I know that from model airplanes engines that run on basically alcohol and castor.