Fuel pipe size 5mm or 5.5mm?

[billdn]

Thought I'd replace fuel pipe,so searched on here and found it needs I.d. of 5.5mm which I've purchased. However it seemed to push on too easily,  so checked diameter of fuel tap after little bump in brass connector and is 5mm , so do I need 5.5mm or 5mm, don't fancy petrol everywhere.  Could be over thinking it?!

[Oddjob]

Normally 5.5mm Bill.

[McCabe-Thiele (Ted)]

The fitting on the carb end is 5.5mm at the waisted center on a slight taper -  the built in olive is around 6 mm but it does seem that 5.5 mm pipe is a loose fit.
If you fit the pipe whilst the carbs are off you can fit a spring type clip.
I fitted mine with the carbs in place so had to use a narrow cable tie - for peace of mind even though the i/d is 5.4mm as its 1/4".



.https://www.ebay.co.uk/itm/140693835989

[ST1100]

I fitted mine with the carbs in place so had to use a narrow cable tie - for peace of mind even though the i/d is 5.4mm as its 1/4".

.https://www.ebay.co.uk/itm/140693835989

As they're not braided: prone of getting kinked?

[McCabe-Thiele (Ted)]

I fitted mine with the carbs in place so had to use a narrow cable tie - for peace of mind even though the i/d is 5.4mm as its 1/4".

.https://www.ebay.co.uk/itm/140693835989

As they're not braided: prone of getting kinked?

Not a complex route from carbs to Petcock - original fitting has a steel coil outer cover. / heat shield

[Oddjob]

Thinking on this. Why are we fitting Nitrile piping when the ethanol in todays petrol will start to affect it within a year or so. Surely we should be looking at Viton piping these days?

I've just bought 2m of 5mm ID pipe from China made of Viton, I'll let you know how it fits when it arrives. They didn't do 5.5mm ID.

[McCabe-Thiele (Ted)]

ATM I use Ethanol Free SUL so not an issue.

Is there a difference in wall thickness?

[Oddjob]

The 5mm has an OD of 8mm Ted, so 1.5mm wall. The nitrile one you listed has a 2mm wall.

The hole for the fuel pipes on a 500/550 carb bracket is 12mm so no problem with any of those going through.

The original pipe was always a tight fit, I remember trying to pull one off the T piece without dismantling the carbs as it was too short after being cut down and I ended up pulling the T piece apart, the joint is just soldered. Maybe the 5mm will be a better fit. we'll see.

[TrickyMicky]

As my speciality is the bleedin' obvious, may I just add that when trying to remove small bore rubber piping, if you just pull the pipe then it stretches slightly and reduces the inner diameter. meaning that it grips like crazy. If you are not going to re-use the pipe, then slice it lengthways. If you want to save the pipe, then try to twist it on the nozzle using a small pair of thin nose pliers.  I was taught this years ago when struggling to remove leak off pipes from diesel fuel injectors.

[billdn]

Well I fitted the 5.5mm pipe with correct clip from DS and turned fuel on at tank and fuel weeped out all over my freshly polished crankcase cover 😤
So maybe my tank has 5mm pipe, which the old one appeared to be.

[Oddjob]

Consensus on the site was 5.5mm Bill, as I haven't yet done mine I just repeated what everyone else had fitted and recommended, sorry.

It was only because I couldn't find 5.5mm in Viton I ordered 5mm or I'd have done the same.

[McCabe-Thiele (Ted)]

Interesting that DS show the original pipe p/n 17681-377-000 as no longer available.
I suspect the original was Imperial based like a lot of early Japanese Car Parts probably 13/64" I/d  so no direct equivalent available.