Topic: cb500 leaky fuel rail- what size o-ring

[tennesseebreeze]

Anybody know exactly what size o-rings I need to keep the t's in the fuel rail from leaking? I have a 73 cb500.

[Kenzo]

It's guuna be an oddball metric size...I saw it on here but can't find it...Doh!

I believe 4into1 has them.

Mine leaked when I first bought the bike and was getting it running but stopped once I got good fuel in it. Glad it fixed it's self because it looks like a PITA to split the carbs.

Cheers,
Kenzo

[tennesseebreeze]

This will be the third time splitting the carbs for this build. Sigh. It's the only thing left before it's rideable. The o-rings I put on look like the right size, but are obviously not snug enough. My big complaint with those o-ring kits you buy with the hundred different sizes- all the small o-rings aren't fat enough. Thanks for responding. I'll check out 4 into 1.

[Deltarider]

Are you sure it comes from there? These T-joints seldom leak, even after the abuse they got from me, the O-rings still seal well and that is after 40 years. BTW, Honda fitted two on each side. Could very well be the fuel line leaks.

Mine leaked when I first bought the bike and was getting it running but stopped once I got good fuel in it. Glad it fixed it's self because it looks like a PITA to split the carbs.

Thats why for hibernation I favor having gas in the system over draining. You will be amazed how far these O-rings can shrink (and swell again).
Now I read yours are not original. Sigh.

[tennesseebreeze]

Are you sure it comes from there? These T-joints seldom leak, even after the abuse they got from me, they still seal well after 40 years. Honda fitted two on each side. Could very well be the fuel line leaks.

Mine leaked when I first bought the bike and was getting it running but stopped once I got good fuel in it. Glad it fixed it's self because it looks like a PITA to split the carbs.

For hibernation I favor having gas in the system over draining. You will be amazed how far these O-rings can shrink (and swell again).

Hmmmm. Not totally sure. But I have brand new fuel line and I just replaced the bowl gaskets with genuine Honda. I'm trying to think where else it would be coming from.

[flybox1]

This is where a good bench carb holder comes in handy so you can hook up an aux fuel supply and really get a good look.
Are you using the correct 5.5mm fuel line or something oversized with a hose clamp?

[Kenzo]

Use the search function above "tee o-ring" a bunch of posts.

Kenzo

[Deltarider]

My guess is this brand new fuel line either leaks (split?) or isn't snug and well connected. If the fuel system has been dry for a long period, the O-rings may swell back to their original size. Just try by giving it time.
Separating the carbs is a virus that runs in this forum only.

[tennesseebreeze]

This is where a good bench carb holder comes in handy so you can hook up an aux fuel supply and really get a good look.
Are you using the correct 5.5mm fuel line or something oversized with a hose clamp?

It is the correct size. Very snug and of high quality. What about the fuel/air screw? Any chance it could be coming from there?

[flybox1]

What about the fuel/air screw? Any chance it could be coming from there?

Doubt it.
you also indicated you replaced the bowl gaskets.  were these round, or shaped to fit your bowl?
if you have a misaligned bowl gasket, it could be hanging a float, which would prevent the float valve from sealing...
check that you dont have a pinched bowl gasket somewhere.

[tennesseebreeze]

What about the fuel/air screw? Any chance it could be coming from there?

Doubt it.
you also indicated you replaced the bowl gaskets.  were these round, or shaped to fit your bowl?
if you have a misaligned bowl gasket, it could be hanging a float, which would prevent the float valve from sealing...
check that you dont have a pinched bowl gasket somewhere.

They are the shaped bowl gaskets, so I doubt they are the culprit. Would a hung up float cause a leak if all the seals are good?

[tennesseebreeze]

I guess my only option is to take the carbs out once again. I should make a setup where I can test them on the bench. I fear the boots will be worn out with all the removal/install. I better brace myself for a vacuum leak too.

[flybox1]

I guess my only option is to take the carbs out once again. I should make a setup where I can test them on the bench. I fear the boots will be worn out with all the removal/install. I better brace myself for a vacuum leak too.

a little lube always makes things go in and out easier 

[meilakj]

would this set help ?

http://www.ebay.co.uk/itm/111619220008?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT#shpCntId

[tennesseebreeze]

Oh snap- good one flybox. Good suggestion too.

[HarborRat500]

I just recently had this same issue leaking at the fuel tee joint between the 3 and 4 carb on my recently new to me 73 cb500k2, as I recently replaced my bowl gaskets as well as a bowl that had a split in the brass overflow tube. It started to leak pretty good out of the tee joint, and after teardown I believe it to be a result of the 10% ethanol I was using had hardened an shrunk the orings. I found metric oring kits at harbor freight that had 2mm ×8mm as well as 1.8mm ×8mm. After first ptrying the 2x8, they seemed a hair to loose, so I used the 1.8x8 which seemed to fit mor snug on the inner diameter and also had a better snug fit putting back into the carbs. It seems so far to be working out ok. Oh and I will be no longer using ethanol gas, no matter what %!!!