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  1. #1
    CB750 Member Neilx7's Avatar
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    New ember new project

    Hi new member.
    I have bought a 1981 CB750f, it has been stood in a garage for the last 20 years, I think it was last on the road in 1991.
    It's a long term project, to spread the cost.
    The engine covers have all been chromed at sometime but as you can see from photos it's long gone.

    I restored a 1979 CBX 1000z a few years ago, which involved total strip down and stripping and rebuilding the carbs and rebuilding the cylinder head,so hopefully the 750 will very much on the same line engine wise etc but a lot smaller.

    Looking forward to asking for advice and tips as thing progress, the forum looks to be a great source for information.

    I enclose a few photos, first thing is see if it runs before I strip it down.

    Cheers
    Neil
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  2. #2
    CB750 Guru amc49's Avatar
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    You picked a max effort project there but some like that. Same as CBX only a little less of it.

  3. #3
    CB750 Member Neilx7's Avatar
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    Yes it's a long term job
    Will try and get it running before I strip it down

  4. #4
    CB750 Member Neilx7's Avatar
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    update.
    I have given the carbs a quick clean, but from the state of them major strip down is required.
    I put them back on and with the help of some carb cleaner and fresh petrol I did get it to chug over which was good enough for me to know the motor seem ok.

    next to remove the 4in1 exhaust, what a task, I had grind off the down pipes and then set about them with penetrating fluid and a rubber hammer, 4 hrs later I won the battle.
    2 of the middle stud's were seized solid to the flanges, but the came off with no damage to the head result.
    I have started to strip the rest of the bike, pics of progress so far.

    Neil
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  5. #5
    CB750 Member Neilx7's Avatar
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    totally stripped the bike, engine on work bench to start cleaning some off the numerous lays of paint to see what under there.
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    before clean up


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    after clean up, once i get the head off I will get it vapor blasted ready for painting.


    cam's, bucket, shims removed, all nuts and bolts removed, to take cylinder head off, but as with the exhaust it going to fight me all the way.
    On the bright side no one has been into the engine, all cam cover bolts like new, unlike the CBX I did which had bolts snapped and threads stripped.

    The cylinder head is stuck fast to the block, so will need to think of away to release it, ??.

    I have read that you can put some cord/rope into the spark plug holes and turn the crank and try and use the piston to lift the head.

    I will need to do something as it will not move, even with penetration oil sprayed down the studs and with blows from a rubber mallet, it stuck fast.

    Anyone got any ideas on a way to free it.

    Cheers
    Neil

  6. #6
    CB750 Enthusiast Chris in Dorset England's Avatar
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    Wait till you get to the cylinder block!

  7. #7
    CB750 Enthusiast Chris in Dorset England's Avatar
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    Quote Originally Posted by Neilx7 View Post
    totally stripped the bike, engine on work bench to start cleaning some off the numerous lays of paint to see what under there.
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    before clean up


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    after clean up, once i get the head off I will get it vapor blasted ready for painting.


    cam's, bucket, shims removed, all nuts and bolts removed, to take cylinder head off, but as with the exhaust it going to fight me all the way.
    On the bright side no one has been into the engine, all cam cover bolts like new, unlike the CBX I did which had bolts snapped and threads stripped.

    The cylinder head is stuck fast to the block, so will need to think of away to release it, ??.

    I have read that you can put some cord/rope into the spark plug holes and turn the crank and try and use the piston to lift the head.

    I will need to do something as it will not move, even with penetration oil sprayed down the studs and with blows from a rubber mallet, it stuck fast.

    Anyone got any ideas on a way to free it.

    Cheers
    Neil
    It's usually the studs corroded to the head, the 4 centre ones are the usual suspects. try removing the outer ones you can then wriggle the head about a little, they will fight anyway. It took me 3 days to get the head / block off. Plus Gas is the best penetrating fluid, on sale via the net. Be careful with the studs, they can breakout the threads in the block.

  8. #8
    CB750 Member Neilx7's Avatar
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    I have finally got the head off by making some pullers by using some spark plugs and welding some 12mm threaded bar to them, and making a plate 5x17 inches out of 5mm plate with 14mm holes in that line up with the spark plug holes in the head. Screwing them in to the spark plug holes fully, and the threaded bar through the 14mm holes in the plate, and resting the plate on the cylinder head studs and threading nuts on, and slowly tightening the nuts down to apply up ward pressure to raise the head, being careful not to strip the spark plug treads in the head, it took an hour of slowly tightening the nuts evenly across the plate and hitting the head with mallets and lumps of wood to free the head, see pics below.
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  9. #9
    CB750 Guru amc49's Avatar
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    If doing the cylinder block you still show a nut on the front center in place; it MUST remove FIRST!

    And the head should have come off easy with what you show there, possible damage to the cam cap flats from that rusty plate pressing on critical surfaces............it's the cylinder block that gives all the trouble coming off.

  10. #10
    CB750 Member Neilx7's Avatar
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    correct ,
    i am not removing the cylinder block, just doing the valves stem seals and lapping the valves in.

  11. #11
    CB750 Enthusiast Chris in Dorset England's Avatar
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    Quote Originally Posted by Neilx7 View Post
    I have finally got the head off by making some pullers by using some spark plugs and welding some 12mm threaded bar to them, and making a plate 5x17 inches out of 5mm plate with 14mm holes in that line up with the spark plug holes in the head. Screwing them in to the spark plug holes fully, and the threaded bar through the 14mm holes in the plate, and resting the plate on the cylinder head studs and threading nuts on, and slowly tightening the nuts down to apply up ward pressure to raise the head, being careful not to strip the spark plug treads in the head, it took an hour of slowly tightening the nuts evenly across the plate and hitting the head with mallets and lumps of wood to free the head, see pics below.



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    Hi, very neat job .

  12. #12
    CB750 Member Neilx7's Avatar
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    cheers

  13. #13
    CB750 Member Neilx7's Avatar
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    update,
    frame and all the brackets, battery box etc off to be blasted.

    restored the front wheel 8 hrs work of cleaning sanding and painting, but well work the effort.

    will start on the cylinder head next week if i can make the time,
    also carb repair kit from www.randakks.com has arrived, expensive when taking into account the vat and import tax and post office charges on top which came to an extra £44 owtch. roll on brexit and a free trade deal with the usa.

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  14. #14
    CB750 Enthusiast Chris in Dorset England's Avatar
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    nice job on the wheels. Carb kit, yes very expensive, but as Henry Royce (Rolls-Royce) said, "The quality remains long after the price is forgotten"

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