CL77 reassembly - couple of questions before we get started
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Thread: CL77 reassembly - couple of questions before we get started

  1. #1
    Senior Member the-chauffeur's Avatar
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    CL77 reassembly - couple of questions before we get started

    After about three months (don't ask), I've got the vapour blasted engine cases back and after flatting the top end mating surfaces and hosing them down/out with kerosene, I'm dangerously close to being ready to start the rebuild. Before I do, there's a couple of things I'd like to check, just 'cos it's easier to ask and look stupid now than, well, you get the idea.

    The questions relate to this diagram:

    CL77 reassembly - couple of questions before we get started-honda-cl77-scrambler-1965-usa305-cylindercylinder-head_bighu0093e8s01_21e4.jpg

    First up, it looks to me like there are no cylinder o-rings - the large diameter rubber bands that sit between the barrels and the base gasket. I'm assuming that's correct, and those o-rings were introduced in later models, but I just want to check that the diagram is correct and that there aren't supposed to cylinder o-rings. Is that right?

    Another thing I'd like to know is what is the point of the vent tube joints (part #18) and the attaching tube (#17)? I saw them when I tore the engine down and couldn't figure out what they were for then, and I'm still none the wiser. I'm assuming they're simply another way of venting vapours along with the top vent (#12), and were deleted from later models when the top vent was widened, but if there's a good explanation somewhere, I'd be interested to read it.

    Finally - at least for now - the parts list indicates there are four sealing washers (#24) and four plain washers (#25) that go under the dome nuts on the tops of the cylinder studs. By my reckoning, one of the sealing washers will go onto the right rear stud, which is clearly the upward oil passage, but I can't figure out what studs the other three sit on.

    There will be more questions, but that'll do for now. Thanks all.
    CL77 (1966)
    CA77 (1966)
    SL350 K0 (1969)

    SL350 K2 (1971)
    CB450 K6 (1972)
    CB750 K2 (1972)

  2. #2
    Senior Member mike in idaho's Avatar
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    Part #18 screws into a passage leading to the intake valve guide. The hose with the Y connection connects to the front of one of the air filters. Its function is to deliver filtered air to the intake guide, that keeps vacuum from sucking oil around the intake valve stem and into the combustion chamber. Honda eliminated this part in later production, they decided it was unnecessary. If you don't have the correct air filter or the other parts to hook it up you can just plug the holes in the head, the engine will run just fine either way.
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    '65 YG1
    '65 CB160
    '66 CL160
    '67 CL77
    '68 TR6
    '69 T100R
    '69 T120R
    '72 Commando 750
    '78 XS650E
    '79 Gl1000
    '81 440 LTD
    My company car is a Kenworth

  3. #3
    Senior Member the-chauffeur's Avatar
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    Thanks Mike - that makes more sense than my assumption. For the sake of completeness, I'll cobble something together so even if the oil filters aren't quite right, it'll work the same.

    Next question is about the points shaft orientation. I've posted this on the SOHC4 forum (other bikes section), but cross-posting here won't hurt:

    I have a horrible feeling about this, and if you know anything about these engines you may be able to guess what comes next . . .

    . . . I've just finished putting together the CL77, and after pulling it apart to re-orient the camshaft (yeah, back to front), I thought I was done and put the engine back into the frame. But it's just occurred to me that there were no discernible marks on the points shaft (or camshaft for that matter) to tell me which way the shaft should fit. Just to be clear, I'm referring to this bit:


    Knowing that spark advancers on later bikes can be oriented the wrong way, the painful realisation has dawned on me that I may have inadvertently put this thing back in 180deg out. Once again, the manuals are absolutely hopeless on this bit. Yay. And yeah, if I've got it wrong, the engine's gonna have to come out again . . .


    So, anyone know how to tell whether the shaft is oriented properly? Fingers very, very crossed that it can be oriented either way (although the way things have gone so far, I highly doubt I'm that lucky).

    Thanks all
    CL77 (1966)
    CA77 (1966)
    SL350 K0 (1969)

    SL350 K2 (1971)
    CB450 K6 (1972)
    CB750 K2 (1972)

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  5. #4
    Senior Member mike in idaho's Avatar
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    The timing mark on the camshaft sprocket is centered at the the top, with the crank at the tdc mark. There is a hash mark on the end of the points cam, it should also point up with the other marks alined. If it's already together and in the frame I would install the points plate to check. Roll the engine over through the compression stroke by hand and see if the points appear to open at the right place.
    '65 YG1
    '65 CB160
    '66 CL160
    '67 CL77
    '68 TR6
    '69 T100R
    '69 T120R
    '72 Commando 750
    '78 XS650E
    '79 Gl1000
    '81 440 LTD
    My company car is a Kenworth

  6. #5
    Senior Member the-chauffeur's Avatar
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    Thanks again Mike. Not exactly what I wanted to hear, but exactly what I needed to know. And no, I wasn't lucky enough to accidentally get it right.

    I'd managed to get the cam sprocket and the crank timing aligned correctly; the one bit I did get from the manuals, and remember from the teardown, was that the big ol' paint dot on the cam sprocket should be at the top when the crank timing mark is at T. But after polishing the end of the points shaft, I found the mark you were talking about and, of course, it was 180deg out. Arse.

    So I've pulled then engine, taken the top off and straightened everything out. Since this was the third time, I got it done fairly fast, and checked everything before closing it up again. It's now back in the frame, with the external engine parts being added as I go.

    I somehow doubt that'll be the last issue, so keep an eye on this thread. Meantime, thanks again Mike.
    CL77 (1966)
    CA77 (1966)
    SL350 K0 (1969)

    SL350 K2 (1971)
    CB450 K6 (1972)
    CB750 K2 (1972)

  7. #6
    Senior Member the-chauffeur's Avatar
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    Electrical cable/HT lead routing

    Next question . . .

    . . . I'm now kicking myself for better documenting the electrical cable routing when I tore the bike down, because I can't work out what the hooks on the back of the cylinder are for - #15 & #20 on this diagram:

    CL77 reassembly - couple of questions before we get started-honda-cl77-scrambler-1965-usa305-cylindercylinder-head_bighu0093e8s01_21e4.jpg

    I have a feeling the two #20's hold the HT leads, although routing them down and under the carbs seems a bit strange to me. I also suspect #15 is for the alternator/neutral switch after they emerge from the right side, but without any reference images, it's hard to tell.

    Any words of wisdom?
    CL77 (1966)
    CA77 (1966)
    SL350 K0 (1969)

    SL350 K2 (1971)
    CB450 K6 (1972)
    CB750 K2 (1972)

  8. #7
    Senior Member mike in idaho's Avatar
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    #20 is for the spark plug leads, they are normally hung on the outboard carburetor mounting studs. #15 is for the breather hose off the cylinder head cover. It comes down through that clamp into a notch on the sheetmetal cover behind the cylinder, under the cover to exit the crankcase casting via a hole by the front sprocket.
    '65 YG1
    '65 CB160
    '66 CL160
    '67 CL77
    '68 TR6
    '69 T100R
    '69 T120R
    '72 Commando 750
    '78 XS650E
    '79 Gl1000
    '81 440 LTD
    My company car is a Kenworth

  9. #8
    Senior Member the-chauffeur's Avatar
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    Ahhhh . . . that answers several questions I didn't know I had . . . thanks again Mike. I hadn't worked out what the small semi-circular cut-out in the top of the cover plate was for, and I was scratching my head a bit about the circular hole in the top of the crankcase that leads to the chain cavity on the right hand side. I'd just assumed it was some sort of surface water drain off point. Having said that, I'm now confused about similar cut-outs to those on the cover plate that are on the rear of the cylinder head fins. There's what looks like a set of semi-circular cut-outs running from top to bottom that are to the right of the centre line, but the breather outlet is above them and to the left. Not sure I understand that design choice, although I wouldn't have thought running a rubber tube that close something that'll get pretty hot is such a great idea.

    A couple more things have come up as I've been piling the parts back on. First, d'you know what size are the split/cotter pins that hold the choke linkage together? They're tiny. Actually, an additional - and possibly better question so I learn something for next time - is how do you measure a split pin? I've got loads of larger ones kicking around, but I've got no idea how they're sized.

    Really dumb question - can you remove/replace the left hand air filter cover with the exhaust on the bike? I'm asking 'cos the sidecovers are off being painted so I can't check for myself, and I'd really rather not go to the bother of fitting up the exhaust if I've got to yank it off again when the covers come back. Can't find anything about this in the books (no big surprise there).

    Slightly less dumb question about the engine castings; what's the bit on the top of the crankcase that pokes up through the sheet metal cover for - the bit with the threaded hole that runs from left to right through it? I'm pretty sure it serves no purpose on the CL's, and I couldn't see what it would be used for on the CA that I'm part way through disassembling. It seems an odd place to mount something, but I guess it'll make more sense when I understand its purpose - and again, can't see any mention of it in the books . . .

    Outright confused question - what's the point of/reason behind the special nut that appears to be used on the underside of the crankcase, where exactly does it fit and why's there only one of them? It's part #18 in this diagram:

    CL77 reassembly - couple of questions before we get started-honda-cl77-scrambler-1965-usa305-upperlower-crankcase_bighu0093e8s04_92f3.jpg

    Last thing for now - I can't find what I've done with the clutch joint (the bit the cable goes through that clips into the side cover). It's definitely in the garage, but I've looked all over the place and can't see where I've put it. If you've got any idea where I might have left it, shout me . . .
    Last edited by the-chauffeur; 06-29-2019 at 12:40 PM.
    CL77 (1966)
    CA77 (1966)
    SL350 K0 (1969)

    SL350 K2 (1971)
    CB450 K6 (1972)
    CB750 K2 (1972)

  10. #9
    Senior Member ancientdad's Avatar
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    Quote Originally Posted by the-chauffeur View Post
    Slightly less dumb question about the engine castings; what's the bit on the top of the crankcase that pokes up through the sheet metal cover for - the bit with the threaded hole that runs from left to right through it? I'm pretty sure it serves no purpose on the CL's, and I couldn't see what it would be used for on the CA that I'm part way through disassembling. It seems an odd place to mount something, but I guess it'll make more sense when I understand its purpose - and again, can't see any mention of it in the books . .
    If I remember correctly, the CA has a 2 piece cover that goes in that area and a sidecover-like bolt with plastic knurled head holds the left half on, but I think the threaded boss from the upper case is where the bolt goes that holds the right half on

    CL77 reassembly - couple of questions before we get started-ca77-cover-engine.jpg

    Quote Originally Posted by the-chauffeur View Post
    Outright confused question - what's the point of/reason behind the special nut that appears to be used on the underside of the crankcase, where exactly does it fit and why's there only one of them? It's part #18 in this diagram:
    I don't know this for a fact, but looking at the 6mm nut (as it is described in the parts fiche) it appears to be an extended-head type of nut that might go in a recessed area in the lower case...?
    Tom

    Ride along at the drag strip - https://www.youtube.com/watch?v=20jFPazXlvU



    running points... because I'm too old for mysteries that begin with pushing

  11. #10
    Senior Member mike in idaho's Avatar
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    The points wire exits the points housing and is tucked between the fins, goes around to the rear and heads upward in those notches in the center, up to the condenser pack. There should be a small grommet on the wire that fits into the lowest notch in the fins. That 6mm cap nut on the bottom goes on a stud that goes into an oilway, it should have a copper sealing washer under it.
    '65 YG1
    '65 CB160
    '66 CL160
    '67 CL77
    '68 TR6
    '69 T100R
    '69 T120R
    '72 Commando 750
    '78 XS650E
    '79 Gl1000
    '81 440 LTD
    My company car is a Kenworth

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