CB500 leaking fuel tap / fuel pipe connection

[Charliecharlcomb]

Hi there,

I replaced the black fuel pipes last year on my CB500 as the old ones had been progressively shortened over the years as I struggled to remove them when removing the petrol tank. The replacements looked fine and fitted well. Having got the bike out ready for spring I noticed there is a leak on the right hand pipe as you look at it from the left hand side where it is connected to the petrol tap. It only leaks when the fuel is on or on reserve. I've moved the wire circlip up to make sure it is gripping the fuel tap but it still leaks. Does anyone think this may be caused by a fault lower down at the carb end? It's only a very slow drip but as the pipe is wet with petrol at the top, it can't be a good thing. Any ideas?

I could replace the fuel pipe again but I'm not sure how I can be confident that the pipe I replace it with will be any better.

[hairygit]

Sad to say it's probably the ethanol in the petrol attacking the pipe from the inside. Damaged fuel lines from ethanol is well documented, evil stuff that fuel companies have been forced to add to it by the E.U. regs stating it has to have 5% ethanol added, and that goes to 10% some time this year, so the problem will get worse. Ethanol resistant fuel line is available, and as usual is much more expensive. Your only safe option is to get some ethanol resistant fuel line and fit it, and make sure the seller guarantees the resistance, to make sure you don't get ripped off.

[matthewmosse]

I've had fuel line fail inside of 6 months, might be ethanol or might be just dud pipe- stored too long in wrong conditions as I had some that was very finely cracked from the off, no time for ethanol to have attacked it - I think the roll must have been exposed to something nasty in storage as replacement stuff from the same ag engineers was ok, came from further into the roll. I now flex it though very tight bends to check for tiny cracks before fitting.I have had the same on diesels and braided fuel lines, seems more common if there are tight bends in the fuel line or if it is situated so it moves a lot / is reguarly disturbed. Best to have plenty of spare line and clips around just in case.

[Charliecharlcomb]

Wow, I had no idea ethanol could be such a problem. The pipe seems very 'slippy' when pulling it off and the leaked fuel that had collected seemed quite oily so this all makes sense. Looks like I will have to take my carbs off again...

Would this do the job do you think? :

http://www.groveclassicmotorcycles.co.uk/0099e-petrol-pipe-black-rubber---ethanol-proof-14-id-1432-p.asp

[hairygit]

That is slightly larger than you need, 1/4 inch id equates to 6.35mm, whereas Honda used 5.5mm id  if my memory is correct.

[Johnwebley]

I used 5mm ID fuel tubing,

 check this out

http://www.ebay.co.uk/itm/Nitrile-Rubber-Smooth-Fuel-Tube-Petrol-Diesel-Oil-Line-Hose-Pipe-Tubing-NBR-1MTR-/140693835989?var=&hash=item6674aa9834

[Charliecharlcomb]

Perfect, thanks!

[deltarider]

I used 5mm ID fuel tubing,

Better look for ⌀ 5,5 mm (standard) as that is already difficult enough to slide it over the nipples of the T-joints. With standard length of 18 and 30 cm (17 and 28 for the later model petcock) there's guaranteed no kinking.

[Johnwebley]

Johns link seems to be for 5.4mm inside diameter piping not the 5mm he mentioned.

  the pipes are soft a flexible,and grip really well,the Ebay section gives you chance to select the size you need,

 I MAY have even used the 4,5 ID tube as the OD is slimmer and curves well !!

[Charliecharlcomb]

I've gone for the 4.5mm. Lets see how well it fits.

[Charliecharlcomb]

Yup, 4.5mm was brilliant. A nice tight fit. Carbs off, fuel lines replaced and refitted in under an hour. I think it took me all day the first time.