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  1. #1
    CB750 Member Andy888's Avatar
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    Cylinder Head Removal about to send me over the edge

    Hi
    This is my first post after lurking around a bit. I have a 1981 750F which has been sat around for some time by the the look of it.
    I have stripped it down to bare frame and thought I'd tackle the engine first. Wont take too long I thought!
    The spark plugs were all very tight but I managed the gently get each started, worked them back and forward and eventually got 3 out. The fourth
    snapped off instantly. Easiouts would not touch it and I decided the whip the head off and send it to the local engineers to remove the plug.
    Anyway as per usual the head is stuck solid on the studs due to corrosion I guess as the studs are exposed to the elements.
    I removed the 2 studs at each end if the head as these are protected from the outside. The 8 that are left will not budge.

    Ive soaked with penetrating oil over and over, beat the head with a wooden block and hammer, tapped all the studs to try and shock the corrosion loose,
    gently tried prising the head up, sworn a lot, beat my head against the wall, and even prayed, but still the b*****d won't move.
    Ive even considered drilling or die grinding through the studs further down in the hope that the head will come off leaving the the top half of the studs in the head. At least then i would have access to the studs on both sides of the head to try and remove.

    Ive had search and it seems that most people manage to remove most of the studs which allows a bit of head movement and that allows the studs to release. But with 8 studs thats not going to happen. Been on it for days now.....arggghhhhh

    Any bright ideas.....anyone.......please.....before I phone the Samaritans.

    Andy

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  2. #2
    CB750 Enthusiast Chris in Dorset England's Avatar
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    Hi, common problem, sloppy design by Honda. Water runs down the spiral studs corrodes the steel and alloy together.
    I had the same thing with my dohc 750. If possible try to extract the remaining studs by double nutting, lots of wd40 or whatever. Be careful not to strip the alloy threading. kero and oil mixed together makes a good release agent.
    Good luck !
    Last edited by Chris in Dorset England; 08-06-2017 at 03:33 PM. Reason: typo

  3. #3
    CB750 Guru amc49's Avatar
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    Odds are if the studs DO come loose they take the aluminum out of the lower cases with them to not have threads there any longer.

    Also, with the water damage picced in that one pic in the exhaust ports, the plug stuck because the cylinder may well be destroyed by water too. Engine may well be unuseable. You got max damage there, looking like to me...................

  4. #4
    CB750 Member Andy888's Avatar
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    Hmmm..... I may keep going until it's definitely scrap. I've borrowed a heavy duty chuck type stud remover from a technician at work, so I'll give the studs another go and see what happens. If not, anyone know of an engine for sale ????


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  5. #5
    CB750 Member Andy888's Avatar
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    Tonight's instalment: I managed to remove 3 more studs with the heavy duty stud remover. So I'm left with 5 now. One of which snapped off level with the head and one which I know is not seized in the head as penetrating oil runs down past it with ease. The 4 problem ones are the middle 4. I think that the rear 2 are probably not too bad as I can see penetrating oil running down past the first section of head and I can move the studs side to side a little. So the front two are the main problem. I have an electromagnetic induction unit at work so I may try that on the bolts in the hope that the expensing and contraction helps break the corrosion.
    Can't hurt to try I guess


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  6. #6
    CB750 Guru amc49's Avatar
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    Usually the front middle two as they get the water off front tire.

    Does that engine turn at all?

    Be glad it's an F, the spiral shank studs on those are the same strength as aftermarket studs you pay big money for. If the standard K type studs you would have likely broken nearly all of them.

  7. #7
    CB750 Member Andy888's Avatar
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    I think (hope) the engine is basically ok. It turns over smoothly and so far all looks ok. There is corrosion in the exhaust ports as it's been sat with the exhaust resting vaguely near the engine so moisture has got in there. Cams and bearing surfaces all look ok. Oil smells ok. Once apart all will be revealed. Hope it's ok after all this stress!!


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  8. #8
    CB750 Guru amc49's Avatar
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    The problem being that at least one exhaust port will always be open and if the pipes were gapped like that likely water in at least one cylinder. It takes only a very minimum of that to ruin a cylinder, pitted cylinder walls pretty much tear up rings in only a few revolutions.

    That stud broken at case will be fits too. CAN be fixed but commonly a butcher effort there scraps the cases as you can't save one only, they are matched and either half bad makes the other bad too. They are machined as a set in paired halves.

  9. #9
    CB750 Member Andy888's Avatar
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    Well success, of sorts. I ended up die grinding through the 4 remaining bolts through the gaps in the cylinder block. This allowed me to hammer the bolts downward through the head which was just enough to allow a bit of movement and eventually I got 3 out. Then I made about 15 wooden wedges which I put around the head. Eventually the head started to move upwards and it came off leaving the seized portion of the last head
    bolt still in the head. I should now be able to get that out with access to both ends of the bolt.
    Next issue is the cylinder block which of course is seized onto the lower sections of the same 4 head bolts. There's only a small portion per bolt so hopefully won't be as bad.
    Looking into the RH bore there is a slightly rougher section towards the top which I'm guess is the cylinder coating worn through. This I assume means a rebore and new pistons?

  10. #10
    CB750 Member Andy888's Avatar
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    Here's a pic of the head and the bad section in the bore



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  11. #11
    CB750 Guru amc49's Avatar
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    Can't tell like that, you commonly take like 400+ sandpaper and lightly clean the rust off to find the true damage underneath. May be OK.

    The cylinder block is always worse coming off than head, remember to remove the one bolt still holding it on above the oil filter, you can see it behind the camchain there. Mixed result there with most of the studs already gone.

    Can't believe how much stuff rusts there, here you never get nearly so much corrosion. The decks are horrible there.

  12. #12
    CB750 Enthusiast Chris in Dorset England's Avatar
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    My life, what a mess! I hope you can get new studs. Full marks for determination

  13. #13
    CB750 Guru amc49's Avatar
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    Myself, having been there enough times, I walk away when I see one with that much external corrosion on it even if free. And I commonly get free ones. Inside the exhaust or intake ports meaning water in motor is worse.

    It can be a learning experience though.

  14. #14
    CB750 Member Andy888's Avatar
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    I am fully expecting to have to decide that another engine may be the best option, but I hate the thought that something has beaten me. And as you said, it's a good learning experience and I'll know what to look out for next time. I have a Ducati 888 which I bought about 15 years ago which had been badly neglected and left outside but the engine was soooo much easier to work on than this!!


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  15. #15
    CB750 Guru amc49's Avatar
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    'I hate the thought that something has beaten me.'

    I am the same way but you tailor that with the thinking that you are smart enough to know when to stop, it being in your best interest to do so. One can do ANYTHING given enough time and money to waste it but that has nothing to do with the worth of a thing, and worth is how one works with things in reality. I have rebuilt stuff like that to last and run fine but the cost will be easily 3-4X what a decent useable engine starting off with will be.

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