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Author Topic: 78 CB550K4 Oil Leak  (Read 1042 times)

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Offline Fridog

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78 CB550K4 Oil Leak
« on: December 28, 2021, 10:02:18 AM »
1978 CB550K4 - Oil slow-leaks from the bottom of the alternator cover when running, riding and cool-down.  While riding, oil flies onto the shifter, and onto my left boot.  Could this be a left-side main seal leak, and if so, is that an engine-out, split-the-cases type of job?  Could the seal be removed with wood screws, etc., without removing the engine?  TIA.
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Offline bryanj

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Re: 78 CB550K4 Oil Leak
« Reply #1 on: December 28, 2021, 11:00:48 AM »
More likely the oil gallery blanking plug O ring or the plug has been fitted backwards.
The seal cannot be removed without splitting cases or utter butchery and definately cant be refitted to bolted u cases without even worse butchery as there is a moulded lip that fits in a groove you cant see
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Semi Geriatric ex-Honda mechanic and MOT tester (UK version of annual inspection). Garage full of "projects" mostly 500/4 from pre 73 (no road tax in UK).

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Offline Stev-o

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Re: 78 CB550K4 Oil Leak
« Reply #2 on: December 28, 2021, 11:13:02 AM »
Quote from: Fridog on December 28, 2021, 10:02:18 AM
1978 CB550K4 - Oil slow-leaks from the bottom of the alternator cover when running...

Have you tried replacing the cover gasket? #2 in the fiche...

https://www.partzilla.com/catalog/honda/motorcycle/1978/cb550k-a-550-four-k/alternator

If you are uncertain exactly where the leak is, thoroughly clean the area and dust it with baby powder and start the motor, you will now easily see the leak

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Offline bryanj

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Re: 78 CB550K4 Oil Leak
« Reply #3 on: December 28, 2021, 11:47:43 AM »
The gasket is not to keep oil in but water out, 550 is not oil filled like the 750
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Semi Geriatric ex-Honda mechanic and MOT tester (UK version of annual inspection). Garage full of "projects" mostly 500/4 from pre 73 (no road tax in UK).

Remember "Its always in the last place you look" COURSE IT IS YOU STOP LOOKIN THEN!

Offline Fridog

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Re: 78 CB550K4 Oil Leak
« Reply #4 on: December 28, 2021, 12:51:23 PM »
Many thanks to all for the quick and thorough responses...

Will check the oil galley to see if that is the source.

I figured that the alternator cover should NOT retain oil, so when I get in there, I will confirm.

Engine-out, split-cases may be too rich for me.  Will post pics of this very nice, low-key mods 550, excellent daily rider (if you can tolerate a little oil on your left boot). 

Thanks again to all... Happy New Year!!!
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Offline goodtryer

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Re: 78 CB550K4 Oil Leak
« Reply #5 on: December 28, 2021, 02:11:42 PM »
Had a similar situation with my 77. Took me an embarrassing amount of time to fix all the leaks but eventually I got it back to leak-free. The good news is that access is easy on this engine.

Turns out I had leaks at three spots: the starter motor seal, the shifter seal, and the oil pump. It was a little deceptive because I also saw oil on the bottom of the alternator cover. I think it was just getting blown around during the rides and was gathering there.

Learn from my mistakes:
1. Inspect all around. Don’t assume there is only one leak.
2. Use Genuine Honda orings. I got to do the shifter seal and oil pump twice after trying aftermarket on those.

I’ll attach pics later. Posting from my phone at the moment.

Cheers
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1978 CB750K
1973 CB500K

Offline Fridog

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Re: 78 CB550K4 Oil Leak
« Reply #6 on: December 28, 2021, 06:06:54 PM »
Thank you for this additional insight.  Do you think each - or all - of the leaks mentioned would naturally flow to the left side?  Def while standing, but also while underway?  Should be warmer later this week, so I will get it out and see!  Thanks!
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Online HondaMan

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Re: 78 CB550K4 Oil Leak
« Reply #7 on: December 28, 2021, 06:14:16 PM »
A great number of leaking 500/550 bikes can be traced to the shifter's shaft where it exits the left side of the engine. The oil seals in many of the modern kits have a 14mm hole in the center: it MUST be a 13.8mm hole instead, as in the original bike. The 14mm seal will always leak oil when the bike is sitting on the sidestand, especially after warmup, collecting a buncha oil under the left cover. The better oil seal kits (not the $15 ones) will have the correct seal.
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Offline goodtryer

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Re: 78 CB550K4 Oil Leak
« Reply #8 on: December 28, 2021, 06:34:12 PM »
Quote from: Fridog on December 28, 2021, 06:06:54 PM
Thank you for this additional insight.  Do you think each - or all - of the leaks mentioned would naturally flow to the left side?  Def while standing, but also while underway?  Should be warmer later this week, so I will get it out and see!  Thanks!

Yes.
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"Tolerance will reach such a level that intelligent people will be banned from thinking so as not to offend the imbeciles."
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1978 CB750K
1973 CB500K

Offline dave500

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Re: 78 CB550K4 Oil Leak
« Reply #9 on: December 28, 2021, 11:40:29 PM »
on old oil pressure sender units they can be loose and need teflon tape on the threads or actually leak from the metal to plastic crimp,these are cheap and it maybe the only leak as it gets everywhere,blows back and looks like shifter seal,pulling off that chain cover a half cup of oil may spill out?
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Offline bryanj

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Re: 78 CB550K4 Oil Leak
« Reply #10 on: December 29, 2021, 12:58:07 AM »
As these bikes get older another commonish leak is the oil pump cover O ring which is not in the parts book, i think it is 46x2
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Semi Geriatric ex-Honda mechanic and MOT tester (UK version of annual inspection). Garage full of "projects" mostly 500/4 from pre 73 (no road tax in UK).

Remember "Its always in the last place you look" COURSE IT IS YOU STOP LOOKIN THEN!

Offline Little_Phil

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Re: 78 CB550K4 Oil Leak
« Reply #11 on: December 31, 2021, 04:04:30 AM »
Quote from: HondaMan on December 28, 2021, 06:14:16 PM
A great number of leaking 500/550 bikes can be traced to the shifter's shaft where it exits the left side of the engine. The oil seals in many of the modern kits have a 14mm hole in the center: it MUST be a 13.8mm hole instead, as in the original bike. The 14mm seal will always leak oil when the bike is sitting on the sidestand, especially after warmup, collecting a buncha oil under the left cover. The better oil seal kits (not the $15 ones) will have the correct seal.
The 13.8mm seal is now sold under p/n 91202-KFL-841
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