Cylinder Head Cover Leak

[Martin6]

Hi All,

I've got some problems!
Photo 1 shows damage to the head to cover's gasket face, from a gorilla previously taking off the head cover (bottom left of photo). The second photo shows the same area on the cover. This was one of my leaks. Is there a sound way to repair this damage and get a seal?

The first photo also shows one of the cover screws still in the head. The screw head sheared. Penetrating oil isn't helping. I have the same problem further round, but this time the screw sheared at its bottom, right at the head face. The ez-out hasn't worked. Any suggestions on these?

The final photo shows how mucky the camshaft, chain, sprocket and valve gear are. Carbon and dirty oil, despite 3 oil changes in 1500 miles. Is this unusually dirty?

Helpful suggestions and advice would be appreciated. Feeling concerned about the state of my motor and whether I'm up to fixing it!

Thanks, Martin

[Nurse Julie]

Blimey, looks like a big rat has been nibbling that. You'll be lucky to salvage it. Black staining is not unusual, it's a sign of very high heat and dirty oil through not doing regular oil changes.
Edit... I should have said you will be surprised how much of that black comes off when cleaned thoroughly but, I doubt it will all come off.

[McCabe-Thiele (Ted)]

In my experience dirty oil can be due to high detergent content such as with oils designed for  diesel engines or bore wear.

Different situation but I know a guy I worked with who bought a Civic Honda Type R that had not been serviced regularly. He put it on the ramp at work he did four successive oil changes running the engine for 15 minutes between changes until it came out pretty clean. He did a final change with a second oil filter. As it was VTEC he did not want to risk flushing oil.

Might be worth using a Silicone based sealer with  new seal to cure the oil leak.

[Martin6]

Blimey, looks like a big rat has been nibbling that. You'll be lucky to salvage it. Black staining is not unusual, it's a sign of very high heat and dirty oil through not doing regular oil changes.
Edit... I should have said you will be surprised how much of that black comes off when cleaned thoroughly but, I doubt it will all come off.

I think a previous owner used a hammer and chisel! The damage goes right across the gasket face of the cover. The damage to the head is on the outside edge, right up to and including the outside edge of the screw hole. I don't know if it would seal, if the cover was sound.

I've found a used cover with good gasket surfaces. I'll try to clean up the outside.

What's the best thing to do about a head? I think it will have to be replaced. I will have to buy 'used'. Are K6's the same as earlier models? I'm thinking it would have to include the valves. Happy to re-lap valves, but not try to cut in for new ones.

Other than ebay, any suggestions on where I might get a decent one?

[Pauarc]

Hi Martin
I had a similar issue with a cb550 I managed to get the gasket face skimmed and put two gaskets there maybe it will be possible for you
Paul

[Bryanj]

The person to ask here is Trigger, try a pm he is usualy about if not on holiday with Julie

[Martin6]

Hi Martin
I had a similar issue with a cb550 I managed to get the gasket face skimmed and put two gaskets there maybe it will be possible for you
Paul

Hi Paul,

It crossed my mind, but I thought I might not get a seal across two gaskets. Good to know it could work. It may be a little deep for a skim, but if I can't find an alternative, that's what I'll try. Can you recommend anyone local to us?

Martin

[Trigger]

Easy to fix if you have the correct tools and the skills. Alloy weld the damage area and mill it back to standard .

To skim this to top surface on a 750, you would have to remove all the valve guides and replace with new ones. It must be spot on as the tach drive needs to mess correctly with the drive teeth on the cam shaft 

[Martin6]

Putting a ruler edge across both the head and the cover, both are showing a fair bit of daylight. The cover is quite deep damage. The head is not so deep, but it's  over a wider area all around the screw hole. Whoever, did a good job on them!

Thanks for the advice. Good to know welding could do it. I don't weld, myself and the head has other issues: two sheared cover to head screws and a sheared exhaust flange stud. All were very rusty.   

I've found a couple of potential replacements (ebay):
- The cover was fairly cheap, with good a gasket face. So I've bought it. Will need a good polish up.
- The head is more expensive, but the seller will accept a return if I'm not happy. The photos show decent gasket surfaces and it looks very clean. It comes with its valves still in. 

So, I'm thinking the route I will take is buy the head, check it is flat, check over and lap the valves it comes with and then build it up with my cam and rockers etc. I'm hoping the valve guides will be OK. Should I replace the valve stem seals?

Any reason this plan may not work? Anything I need to look out for?

[Trigger]

The 750 sohc has many different heads. You must get the correct one 

Everything needs to be measured up, valve guides, valves, seats inspected, re-seal the tower studs and you change the valve seals as standard. If you need a good rocker cover contact Julie as she has many in stock and will be cheaper 

[Martin6]

The 750 sohc has many different heads. You must get the correct one 

It did say for 1976 year, but I guess that's buyer beware territory! It does have the extra hole for the front centre 6mm bolt. Is there anything else specific to look for, to check it'sthe correct version?

Thanks for the checklist. 👍