Topic: Carb O-rings connecting to T fuel joint

[ron.cieri.313]

Hi all... it's be awhile as I fell in love with my 2020 Goldwing...but anyways, woke up my 1976 CB750 from a 2 year storage slumber and found a gas leak. The leak originates from the bottom of the T joint fuel linkage between carbs 3 & 4...the side leading into carb 4.

From the parts diagram it looks like there are two o-rings on each side of the T joint which leads to each carb.

Are these o-rings typically included in carb rebuild kits?...as an individual part#'s are not shown on the parts fiche.

Thanks, ron

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[Don R]

 I think the o rings are an odd size. I'm not sure of the quality but here are some. https://www.ebay.com/itm/293417663068?var=0&mkevt=1&mkcid=1&mkrid=711-53200-19255-0&campid=5338590836&toolid=10044&customid=3ed70d3ce83a11819802694b5e482747

[willbird]

Hi all... it's be awhile as I fell in love with my 2020 Goldwing...but anyways, woke up my 1976 CB750 from a 2 year storage slumber and found a gas leak. The leak originates from the bottom of the T joint fuel linkage between carbs 3 & 4...the side leading into carb 4.

From the parts diagram it looks like there are two o-rings on each side of the T joint which leads to each carb.

Are these o-rings typically included in carb rebuild kits?...as an individual part#'s are not shown on the parts fiche.

Thanks, ron

I just got Genuine Honda rubber parts kits and they had those O rings included. Others have said that the Harbor Freight O-Ring kit has the required O rings included for those T's. The rubber parts kits for all 4 carbs was kind of expensive.

https://www.ebay.com/itm/293416780136

[BenelliSEI]

Ron….. On the advice of someone on this forum, I bought a bag (qty.100) of these “0” rings on EBAY a while back. For $10-12, have a look there.

 What my wife calls “SABLE”. Supplies above and beyond life expectancy!

[ekpent]

As member BennelliSei (John) has found out sometimes those o-rings heal themselves when exposed to gas again. I have bought a large quantity of them off e-bay and replace when I have a bank torn down. If I am saying the size right a 8mmx2mm will work times 8 pieces per carb for the roundtops.

[ron.cieri.313]

Thank you everyone...I forgot how helpful and knowledgeable people are on this site...lots of options per your input and it's greatly appreciated.

Interesting thought that they may heal when exposed to gas...may test that theory while waiting to find the time to take off the carb bank...but now I least I can get the part.

...will let ya all know how it turns out...thx, ron

[CycleRanger]

I'd like to find these in Viton.
Viton seems to be the only thing that will reliably hold up to "modern" fuels.

[BenelliSEI]

I'd like to find these in Viton.
Viton seems to be the only thing that will reliably hold up to "modern" fuels.

Pretty sure the ones I found were Viton.

[ZTatZAU]

Hi all... it's be awhile as I fell in love with my 2020 Goldwing...but anyways, woke up my 1976 CB750 from a 2 year storage slumber and found a gas leak. The leak originates from the bottom of the T joint fuel linkage between carbs 3 & 4...the side leading into carb 4.

From the parts diagram it looks like there are two o-rings on each side of the T joint which leads to each carb.

Are these o-rings typically included in carb rebuild kits?...as an individual part#'s are not shown on the parts fiche.

Thanks, ron

I recently went through this on my 1971 CB750 K1 resurrection.  As others have advised the OEM fuel tee o-rings are 1.9x7.9mm but 2x8mm o-rings may better tolerate ethanol laced fuel and are likely easier to find generically.

I opted for one of these kits...

https://www.partsnmore.com/parts/honda/cb750k/?q=48-0791

... for about $7.  The kit included the 8 fuel tee o-rings and 4 drain plug o-rings.
Delivery was fast and they seemed to work well.

ZT

[Deltarider]

These O-rings rarely fail. Mine are still the ones the bike got on the assembly line in 1976. Having the fuel system in a natural state, which is wet, certainly helps a lot. The only winter I had my carbs drained, seals shrinked and were leaking the next spring. Luckily they repaired themselves after I had opened the petcock, but it took some minutes. So first step is to open the petcock, expose them to gas and let them swell up again.

[willbird]

These O-rings rarely fail. Mine are still the ones the bike got on the assembly line in 1976. Having the fuel system in a natural state, which is wet, certainly helps a lot. The only winter I had my carbs drained, seals shrinked and were leaking the next spring. Luckily they repaired themselves after I had opened the petcock, but it took some minutes. So first step is to open the petcock, expose them to gas and let them swell up again.

Mine from 1972 still had some flexibility after all those years. I wanted to check that system and make sure no gunk was in there. I pulled apart a rack of carbs from a 73 bike and the T's had gunk in them, as did the carbs.

[Johnie]

Napa #727-2605 fit the T...I think that number is good on all the sohc4s. That particular o- ring works for the 750 for sure. They've been on my bikes for 15 years and never failed.

[ron.cieri.313]

Thank you for all the supply ideas links and specs...I like those o-rings kits but could to have the specs in case I want to load up.

My 750 is stored in my place in northern michigan
I'm pretty fastidious about draining the carbs because she can sits for weeks between runs even when she is "in use."

However, I didn't think about seals orings and such withering away. It's funny too...cuz I drained the fuel tank after I found the leak on my last trip up thinking I was going to pull her apart...now I'll put some gas back ND see what happens.

Thanks all
Ron

[ekpent]

Napa #727-2605 fit the T...I think that number is good on all the sohc4s. That particular o- ring works for the 750 for sure. They've been on my bikes for 15 years and never failed.

I knew you had that NAPA number stashed away in your brain Johnie.

[Johnie]

In all honesty Eric I had to pull out my KO work records to find it....LOL

[newday777]

Hi all... it's be awhile as I fell in love with my 2020 Goldwing...but anyways, woke up my 1976 CB750 from a 2 year storage slumber and found a gas leak. The leak originates from the bottom of the T joint fuel linkage between carbs 3 & 4...the side leading into carb 4.

From the parts diagram it looks like there are two o-rings on each side of the T joint which leads to each carb.

Are these o-rings typically included in carb rebuild kits?...as an individual part#'s are not shown on the parts fiche.

Thanks, ron

The orings are included in the gasket set from Honda, #1 on the fiche. (4 kits needed to do all 4 carbs)

https://www.southsoundhonda.com/--xpartsstream#/Honda_Powersports/CB750KA_(76)_750_FOUR%2c_JPN%2c_VIN%23_CB750-2540001_TO_CB750-2575894/CARBURETOR/b3d05c73-22e7-4620-b018-132301d96b6e/2956d6f0-ff36-4614-8698-9bd31eb1e621/y

[commander60]

Are the PD carbs o rings the same as the round tops ?

[madmtnmotors]

Are the PD carbs o rings the same as the round tops ?

I believe so, except the early carbs use two o-rings on each end while the PD carbs only use one o-ring on each end of the crossover pipe.

[ron.cieri.313]

FYI all...they resealed themselves!...instead of tearing apart carbs, I was able to take her on a nice ride. It feels a little like magic, but I'll take it

[newday777]

Nice!