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  1. #1
    CB750 Enthusiast 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 Enthusiast 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 Enthusiast 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 Enthusiast 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 Addict Chris in Dorset England's Avatar
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    Wait till you get to the cylinder block!

  7. #7
    CB750 Addict 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 Enthusiast 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 Enthusiast 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 Addict 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 Enthusiast Neilx7's Avatar
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    cheers

  13. #13
    CB750 Enthusiast 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 Addict 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"

  15. #15
    CB750 Enthusiast Neilx7's Avatar
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    had the frame blasted to get shot off all the rust, then i sanded it down ready for my mate to painted it, I am on with doing the back wheel just need a fine day to give it the final satin coat, then i can start putting a rolling chassis together.

    frame and all the brackets.
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  16. #16
    CB750 Enthusiast Neilx7's Avatar
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    update,
    back wheel now restored, started on the carbs, they were bad, well 17 years just been stood i would expect that.
    stripped them down, had them ultrasonic cleaned by a local firm £80 no to bad £20 a carb.
    the outside were well pitted as ultrasonic only does so much, so i have set about cleaning the outside myself.
    I had seen an ad on uk tv for some stuff called cillit bang lime and scale, some american guy is in the ad,s don't know who he is ?.
    so i soaked one of the float bowls in the stuff for 10 mins, then a rub with some fine wire wool and soaked in some water for 5 min to get rid of cillit bang,
    and the results are quite good, see pics.
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  17. #17
    CB750 Enthusiast Neilx7's Avatar
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    update
    carbs now all rebuilt which took about 25hrs in total but well worth it, I have covered them inside and out with acf50 that should keep them in a good condition,
    as they wont be used for quite sometime,
    also stripped the old clear lacquer and corrosion from the 2 alloy foot rest mounting plates and gave them a quick polish also covered with acf50.
    I guess next job will be to strip the cylinder head and replace the guide oil seals and lap in the valves.
    folk tubes have been sent off the be ground and re-chromed.
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  18. #18
    CB750 Enthusiast everready's Avatar
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    Nice work. When do you plan to fire up your bike?

  19. #19
    CB750 Enthusiast Neilx7's Avatar
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    it is a long term project due to the costs, there are lots of expensive item to buy like exhaust, chain sprockets, tires, and getting the tank and paint work sorted.
    plus the last owner had the engine covers chromed, which has now flaked off and chrome alloy corrosion are not a good mix left for 20 years. a local company can remove the chrome but I don't know what the cost will be for that yet. I will start putting the rolling chassis together when i get the folk tubes back in a few weeks time.
    so I guess it will be over a year before it gets fired up.

  20. #20
    CB750 Addict Chris in Dorset England's Avatar
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    Anything to do with these bikes is expensive and long term. One piece at a time!

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