Topic: Carb orings leaking...again

[TurtleSnifferII]

What is the trick that y'all do to keep your carb orings from leaking on the fuel real? They seem to only last for 3 months or so until one of the begins to leak. I have used actual oem honda ones as well as the metric kit of orings from oreilly's. If the orings dont touch the gas for a few weeks they seem  to dry out and leak faster. I'm running the PD50B carbs.

Thanks

[caluser2000]

The original carbs on my '76 CB550 carbs didn't leak issues until they had around 140,000kms up.

When I got my bike back on the  run around 16 months ago I did not reburb those original carbs. I just dragged a set of CB500/4 cards I had in storage wrapped in a dry towel for over 20 years. Opened up the carbs, which were clean inside, and gave all the seals a squirt of CRC556. I then fitted them to the CB550F without connecting the air box, Then connected the card fuel hose to the new fuel tap with the half full of fresh  fuel along with fitting a  freshly charged battery. Undid the float bowl drain screws, turned the fuel tap on making sure there was fuel flowing to carbs. Refitted the float drain screws  Wound in the carb throttle stop screw about 7mm, half choke, turned on the ignition, pushed the starter button and it fired right up.No leaks at all.

No fuel leak issues at all since then either after around 15 months and around 11,000kms.

[caluser2000]

We need more info:

Your climate conditions, how are you storing it, for how long are you storing it, what fuel are you using in it, are you using any additives in the fuel, what is the condition of your carbs and tank. What bike are you running -ie year and model etc etc etc.

Oh and where are you situated. Some member might live reasonably close by and be able to assist you in person.

[jonda500]

To completely eliminate leaking past the fuel T rail o-rings on mine (627B carbs rebuilt by harisuluv), the trick is to always leave the fuel tap in the ON position (or reserve if the fuel level is getting close to going onto reserve) whenever leaving it parked for more than a day or so.
If I park it with the fuel tap turned OFF and then don't end up riding it for a while, the next time I turn the fuel on the carbs leak badly due to the o-rings having dried out and shrunk. This doesn't happen to my other 500 which still has the original 50 year old oem o-rings. Also doesn't happen to my 550 which has Carburettor Keith rebuilt carbs (obviously he must have used the correct type of o-rings!).
John 

[TurtleSnifferII]

We need more info:

Your climate conditions, how are you storing it, for how long are you storing it, what fuel are you using in it, are you using any additives in the fuel, what is the condition of your carbs and tank. What bike are you running -ie year and model etc etc etc.

Oh and where are you situated. Some member might live reasonably close by and be able to assist you in person.

Bike is a 1980 cb650. Bike is stored in the garage in Southern California and I run the 89 octane gas which has ethanol in it. (no choice there) Tank is completely free of rust and carbs work well except for the constant leak that pops up every now and then until I change to new rings.

My situation is exactly what the last post above me said. I have to leave the petcock on or else the orings get dry up shrink and leak. For a bit they will work again after they leak and expand again but that fails eventually. I'm wondering if people use a certain type of oring to get around that.

[Bodi]

My theory is that the ethanol is causing this. I have been exclusively using gasoline without ethanol in my old bikes (and other old engines) for several years after two episodes of the fuel rails leaking, finding both o-rings cracked on one tube each time. before ethanol I had never seen this problem.
As you know, the SOHC4 carb fuel rail o-ring replacement itself is super simple but getting at those seals is a PITA.
I tried to find Viton o-rings but couldn't, haven't been looking since I started avoiding ethanol.
One common brand here (Shell Canada) has premium fuel with no ethanol so it isn't hard to find. For now.
I should get a real fix.
If anyone knows a source for these small o-rings in Viton, I'm interested. I did find a source but needed to order 500 or 1000 - and that was not cheap. I don't ride enough now that the fuel price premium is a big deal but Fearless Leaders could make ethanol mandatory in all motor fuel at any time.
I think all the rubber seals in the fuel system should be replaced if possible, but I haven't seen any seal kits that aren't the black (nitrile?) material that swells in ethanol and probably eventually hardens. And what about the petcock swiss cheese washer?

[Deltarider]

If anyone knows a source for these small o-rings in Viton, I'm interested.

In Holland Gerben, who rebuilds CB carbs, does them, but I don't know if he'll ship transatlantic. Maybe he even stopped supplying those that have chosen to live in 'splendid isolation'.
BTW, the problem is not so much the ethanol itself, the problem is ethanol after the use of conventional gas.

[bryanj]

Nurse Julie does carb sets for the 400/500/550 not sure if she would sell just the tee ones seperate. Ask she is on here as well as UK site

[maxheadflow]

My theory is that the ethanol is causing this. I have been exclusively using gasoline without ethanol in my old bikes (and other old engines) for several years after two episodes of the fuel rails leaking, finding both o-rings cracked on one tube each time. before ethanol I had never seen this problem.
As you know, the SOHC4 carb fuel rail o-ring replacement itself is super simple but getting at those seals is a PITA.
I tried to find Viton o-rings but couldn't, haven't been looking since I started avoiding ethanol.
One common brand here (Shell Canada) has premium fuel with no ethanol so it isn't hard to find. For now.
I should get a real fix.
If anyone knows a source for these small o-rings in Viton, I'm interested. I did find a source but needed to order 500 or 1000 - and that was not cheap. I don't ride enough now that the fuel price premium is a big deal but Fearless Leaders could make ethanol mandatory in all motor fuel at any time.
I think all the rubber seals in the fuel system should be replaced if possible, but I haven't seen any seal kits that aren't the black (nitrile?) material that swells in ethanol and probably eventually hardens. And what about the petcock swiss cheese washer?

Don't know the O ring size you are dealing with but McMaster has some metric O rings in Viton.

[PeWe]

I used this Viton o-ring for my K6 carbs.  Might be same size for other carbs?
2x8 mm 50 pack not that costly as other charge for viton o- rings.
Tight fit, a little lube helped the assembly.

https://www.ebay.co.uk/itm/Metric-Viton-Rubber-O-Rings-2mm-Cross-Section-1mm-30mm-ID-UK-SUPPLIER/141455807170?ssPageName=STRK%3AMEBIDX%3AIT&var=440603747321&_trksid=p2057872.m2749.l2649

[TurtleSnifferII]

Thanks for the replies. The viton orings look good but I'm not sure of the correct size since the old ones were like rocks and shriveled. The ones I use now are 5mm ID with a 9mm OD and 2mm cross section. I think it should be 3mm thicker though since the others look a little too thin. I'll try both and report the results when I get them. Nothing else to lose except some money.

[PeWe]

There is no chart with all o-rings needed for your bike's engine with carbs?

As posted on this forum for CB750 many years ago. Stock size and alternative size where possible.

[TurtleSnifferII]

I havent seen that chart but that would be great if there is one. As for the orings I used the viton oring kit from HF. The proper size was a little too thin so I double stacked them in the groove and they were a nice snug fit. I havent had a single leak since then and I am happy. I can leave the petcock off and not have to worry about the seals drying up and leaking.