CB550K1 head gasket & O ring replacement advice please.

[Brian.]

Hi all,

I have a 1975 K1 CB550, which has a slight oil leak from the cylinder head gasket joint at each end.  I've had this bike for about 14 months, and it's had this leak since I bought it.  I've always put up with it because I'd rather ride the bike than take it all to bits!  However, because I can't ride any of my bikes at the moment I might as well sort it out now.

I bought the bike from a friend who restored it, including rebuilding the engine.  There's a folder full of receipts, including the receipt for the gasket set he used; it was non-genuine.

I suspect, from reading on here, that the leak is coming from the O-rings at either end of the head gasket.  I intend to use a genuine Honda head gasket, probably from DSS.

My question is, does this gasket come with the O-rings?  I can't see them on Silver's website, either with the gasket or separately.

So, does anyone know what size O-rings I will need please?  And do I need Nitrile rings, or Viton, or something else?

Any information or advice will be very gratefully received.

Thank you, Brian.

[Bryanj]

Before you do that check the oil is not coming from under the end caps on the cam cover, the bolt that holds the steel bracket that the cap screws to is supposed to have a soft alloy washer between the bracket and cam cover which can leak and cause the symptom you have.

O rings are a seperate part and number is in parts book.

Have you read the manual carefully?

[Brian.]

Hi Bryanj,

Thank you for replying.  I have a Haynes manual, I've read the relevant section in that.  At this stage, I was checking to see the availability of the necessary parts before I start stripping it down.  I'll study the manual more closely, stage by stage as I do the job.

Being an infernal optimist I was rather hoping that the problem could perhaps be sorted by re-torqueing?  But I can't see me being that lucky!

I don't think the oil is coming from under the end caps but I will check again as you recommend.

There is varying advice on the internet, as with so many things; from just replacing the O-rings & re-using the old head gasket (that is on an American forum) through to ripping the lot down and changing base gaskets too.

I'd rather not go that far, bearing in mind that the bike hasn't done many miles since the engine was rebuilt so I'm hoping nothing is stuck too tight!

There are reports of aftermarket gaskets being trouble free - but mine isn't!  So I was hoping that by replacing mine with genuine Honda, plus fitting good quality O-rings, that I could put the problem right.

But all advice is gratefully received.

Thank you, Brian.

[Bryanj]

Take the Haynes manual and light a bonfire with it!! Go th the Alladins cave section and download the genuine one and parts book that i scanned and Ash stored.
Read, re read then read again the section about refitting cam cover, then come back and tell us what you think it says and i will agree or not. Get it wrong and you will have bent valves and broken valve guides!!!!
If you go to the US  site Hondaman on there has been saying for some time that newer gaskets (since removal of asbestos type materials) are thicker than original which means you need thicker O rings to get a seal.

Retorque was never in a Honda manual and i never have done it.

PM me direct or my email is in my profile if you want any other help.

[Trigger]

If it is leaking from the end caps, as Bryan has said, check the alloy washers top and bottom on the end bolts.
The problem with aftermarket gasket sets is the O'rings in the kit are low quality.
Make sure the end brackets are on the correct side, they are market L & R. Push them back as you tighten up the end bolts. Replace the cap O'rings with a good quality O'ring and smear some red rubber grease on to make them go in easier and seal.

[Brian.]

Take the Haynes manual and light a bonfire with it!! Go th the Alladins cave section and download the genuine one and parts book that i scanned and Ash stored.
Read, re read then read again the section about refitting cam cover, then come back and tell us what you think it says and i will agree or not. Get it wrong and you will have bent valves and broken valve guides!!!!
If you go to the US  site Hondaman on there has been saying for some time that newer gaskets (since removal of asbestos type materials) are thicker than original which means you need thicker O rings to get a seal.

Retorque was never in a Honda manual and i never have done it.

PM me direct or my email is in my profile if you want any other help.

Hi again Bryan J.  Thank you again for replying, and apologies for the late reply.

I do take your point about the Haynes manual  - it came with the bike.

Thank you also for directing me to the Aladdin's cave - what a fantastic resource!  I've downloaded both the Honda manual and parts book.  Brilliant.

I think the part you you refer to about bent valves and damaged valve guides must be figure 87 on page 32 regarding the tappet adjusting screws not correctly contacting the valves - ouch!  Is that what you mean?  And would it help reassembly if the adjusters were backed off before removing the cam cover?

But before doing anything I'll definitely recheck that the leak isn't coming from the end covers.  I've not ridden my 550 since the Autumn, and with hindsight maybe I at least partly assumed it was leaking from the head.

I do appreciate your advice and help, thank you.

Regards, Brian.

[Brian.]

If it is leaking from the end caps, as Bryan has said, check the alloy washers top and bottom on the end bolts.
The problem with aftermarket gasket sets is the O'rings in the kit are low quality.
Make sure the end brackets are on the correct side, they are market L & R. Push them back as you tighten up the end bolts. Replace the cap O'rings with a good quality O'ring and smear some red rubber grease on to make them go in easier and seal.

Hi Trigger,

Thank you too for this, I'll have a good look at these O rings & alloy washers before I do anything else.  As on my reply (above) to Bryan J, I think I perhaps partly assumed it was the head gasket leaking, having read somewhere else that there had been problems in the past with head O rings.

I appreciate your advice, thank you.

Regards, Brian.

[Brian.]

The part number for the O-Rings which go in the oil passage space on the cylinder head gasket is 91301-323-000 and is listed as 5 x 2.4. For some reason the 550 parts books don't show a part number but the 500 parts book does.

Hi Oddjob,

Thank you for pointing this out, I'm hoping that the leak turns out to be from the end caps, but if it isn't then I shall need to order these.

Thank you for your help, kind regards, Brian.

[paulbaker1954]

Hi
Having had exactly the same issue as you here is my advice..

1) Use only OEM Head Gasket and O rings. I had bad experience with the DSS aftermarket set

2) Once the head is off I would recommend getting it skimmed to ensure it is flat. Shoul not cost a huge amount at a reputable machine shop (mine was £30 if I recall)

3) Read the manual Ash recommends and take your time especially with refitting the cam cover and cam chain etc to make sure you get valve timing right.

[Brian.]

Update - it's all done.

I did suspect that my oil leaks were caused by the O rings at each end of the head gasket being the wrong ones.  However, I was wrong; the leaks were caused by there being no O rings in there at all!

I would like to thank Bryan J of this parish.  Part of his reply to my original posting was "my email is in my profile if you want any other help" and he promptly answered every one of my emails - I'm very grateful, as I am for the manual and parts book in Aladdin's cave.

I didn't help myself by dropping a nut down the camchain tunnel either - but that's another story.

Thank you also to Paul Baker 1954, Oddjob, and Trigger.  The head had been skimmed already, so I didn't have it done again, and I bought Viton O-rings from Seal Supplies in Loughborough.

I am really pleased that it's done and to be honest I am pleased with myself I've done it myself! 

Thank you again to all those who offered help, it was indeed very helpful.

Best wishes, Brian.

[Bryanj]

Always a good feeling and they aint that difficult

[paulbaker1954]

I didn't help myself by dropping a nut down the camchain tunnel either - but that's another story.

Sounds fun, I always now stuff a cloth in that hole when working on my top end having once dropped a battery from my head torch down there which luckily I managed to fish out.

Experience is a journey in life

[SteveW]

The magnets we have a work are pretty powerful. They vary from 1.5 Teslas to 7 Teslas.

You stick something to them, you will never get it off.

[Brian.]

Get yourself a telescopic magnet, most powerful one you can find on E-Bay. Comes in very handy for fishing out dropped nuts etc Also works for fishing shims out of buckets on later bikes.

Thank you Oddjob, that's almost identical to the one that I retreived it with!

Brian.