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Discussion Starter #1
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:

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.
 

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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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Discussion Starter #3
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
 

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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.
 

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Discussion Starter #5
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.
 

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Discussion Starter #6
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:

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?
 

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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.
 

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Discussion Starter #8 (Edited)
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:

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 . . .
 

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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

CA77 cover on engine.jpg

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...?
 

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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.
 

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Discussion Starter #12 (Edited)
Looks like a couple of us posted at the same time . . .

Great spot on the engine covers Tom. I have those parts, but they weren't bolted on when the bike came to me. They've been hidden in bubble wrap after powder coating and it never occurred to me they were held on to the upper crankcase by anything other than the centre pin that keeps them together. After unwrapping them, it becomes obvious what that crankcase mounting point is for. I think I've said it before somewhere else, but it's intriguing to see the design choices Honda made with these bikes and how they changed before they really hit their stride manufacturing the later CB/CL models. The different style engine coverings for the CL/CB/CA72s and 77s must've cost them enough to make them redesign the crankcases for later models in such a way that they didn't need covers.

As for the nut, I thought I'd turn over the CA engine I've got in the garage to see whether I could glean any more useful information (yeah, I know - why didn't I do that before? Dunno. Just stupid I guess). Not sure how big this will render, but you can see it in this image - it's the second nut down from top and just to the right of the centre line; it looks blanked off:

CA77 lower crankcase.jpg

Mike - thanks for the insight on the cap nut. It's only now you've said it that I realise the significance of its location. The stud it caps off runs through the passage that sends oil to the side cover and up into the clutch assembly. Makes more sense when you look at the lower crankcase from the side. The one on the underside of the CL engine was missing when I pulled it apart, so I'll rectify that (and the sealing washer) before running it.

There are a couple of odd things in this picture, and they're to do with the bigger nuts towards the left hand (front) end. First up, the top nut as you look at the image is loose (like a couple of threads away from the case), for no very good reason I can see. And perhaps more peculiarly, the two central nuts are domed like the ones that cap the cylinder studs at the top of the engine. Again, if you look at the fiche, there's no logic to this - all of those nuts should be the flat type. Don't get me wrong, I'm not complaining about them - and I may well end up replacing all of them with domed nuts given the exposure the underside of this engine gets - it just strikes me as a bit weird . . .

And thanks for the routing information. I'll check out whether the grommet is still attached in the morning.
 

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Discussion Starter #13 (Edited)
CL77 - swapping thin engine studs with heavy duty replacements

Looks like I'm going to have to pull the engine again and tear down the top end <sigh> . . .

At some point, a PO has done something to the engine studs, and the one on the front left (when viewed sat on the bike) isn't in far enough - either that, or the wrong length stud has been used. I've punched a hole in the top of two cap nuts trying to torque them down and even with two washers, it's not tightening sufficiently - I can basically keep tightening well past the point where all the other stud nuts have stopped. And when I take the nut off, the bottom end of the threaded section can be seen above the height of the top of the engine, and that ain't right. I'm also assuming threadlocker has been used 'cos it's not moving.

So two questions today:

- how do I safely remove a stud held that's firmly held in place with threadlocker? I'm guessing I'll need to apply direct heat (evenly and without going bananas) with a blowtorch to get it free. I've got a couple of sets of stud extractors, although I've never found them particularly reliable when used on butted end studs that aren't a uniform width, so I'm thinking I might need to bend the stud at right angles halfway down to give me something to leverage for the first half turn or so. And no, double nutting has absolutely no effect on it right now. One way or another, I'll be replacing the stud, so tearing it up to remove it isn't going to be a problem; and

- is it safe to replace the thinner front stud that's giving me grief with a heavier duty stud (uniform width) of the same length ? I realise the other front stud is the main upward oil way, but if I can, I'd prefer to replace both at the same time. I've done that same mod on my SL350s with no adverse effects, but I don't know how effective the oil pump on the CL is.

Thanks in advance.
 

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I would torque a plain nut down on the sealing washer, then grind off the extra length of the stud, then it will be short enough to accept an acorn nut. Removing those studs,with the engine assembled is asking for trouble, ruin the threads in the crankcase or twist the stud in two and you will be stripped down to the cases again to fix it.
 
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Discussion Starter #15 (Edited)
Thanks Mike.

Clearly, that blindingly obvious idea hadn't occurred to me, and it makes all kinds of sense. And apologies for not being clear earlier - when I said I needed to pull the engine, I meant pull it out and pull the top end off; for the reasons you've said, there's no way I'd attempt to remove the stud with the top end on. If I'm going to those lengths, I'm going to do it properly.

After having another look at the stud, I don't think that's an option. Here's what I'm looking at:



I'm sure you'd agree this isn't right. Even with the washers removed (for clarity) I don't remember the top of the stud being that high above the deck when I started and no matter how much I tighten a nut on it, it's not reaching torque. The stud itself still doesn't seem to be moving - certainly not when I've used a spanner to see what's going on - but I'm at the point now where I really don't want to tighten it any more. It's almost as though the stud is stretching, but I can't believe it would stretch quite so easily.

If I cut the head off now, I'd need to cut the stud down to the point where there's only a couple of threads left in order for the base of the acorn nut to reach the washers. I've had that trouble before with other 350 engines where the studs weren't seated properly; the acorn nuts would top out and not provide enough clamping pressure on the cases. So whether it's OCD kicking in, I dunno, but I think I'm resigned to pulling the engine, taking the top off and working out why I'm not getting a proper torque reading.

That being the case, any suggestions on removing the stud and/or what to replace it with?

Cheers
 

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I would agree...this isn’t right. Based on what you’re reporting and what the pics show, it’s my opinion that the top end and cylinder needs to come off now rather than later. I’d suspect that stud is pulling out. It might be a prior hopeful “repair” to the upper case (or stud base) now revealing itself? I wouldn’t cut the stud as it seems that really won’t accomplish much. Time to get to the bottom of this...literally, then see what you’ve got, and go from there.

On the left side AF cover question; The four head pipe bolts can stay on, but super loose. But the rear bolt between the exhaust shields will have to be removed. Trying to fish it behind the pipes is risky to your new paint...but it can be done.
 

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Discussion Starter #17
Back again. The good news is that the case isn't damaged. It took quite a lot of heat, penetrant and patience to force the stud to let go, but when it did, it came out relatively easily. The stud wasn't twisted or bent, and for the most part, looked pretty unscathed. Which is all the more strange when you look at what I found . . .

This is the good stud (that sounds weird) - the one that's the right height and staying put - as measured from the deck/top of the engine case:

IMG_0534.jpg

This is the one that I removed 'cos it was poking just a little too far out of the top of the engine; it's measured from where point where it would be if it was inserted into the deck/top of the engine:

IMG_0535.jpg

(Can you tell I don't understand how image rotation works here . . . ?)

So there's around 2cm difference in overall length. How does that work? Given how tight the stud was in the hole, and how undamaged it looks, this makes no sense to me. The conclusion I've come to is that either there's some sort of spaghettification going on with the stud where it's stretched, or one of the POs has put the wrong stud in and hoped no-one would notice.

I really can't see a stud like that stretching as much as it did without losing tension in other planes, so I guess the PO theory is the one to go with. One possible explanation is that those studs aren't cheap. I got the last one on Silver's shelves and it cost something like $20. CMS have more, but their price is around $50 each.

But the big thing for me is that the case is fine . . . so aside from being put back a few weeks time-wise while I wait for replacement bits to come in, we're all good.

Next up, carb cap questions. I have a feeling mine aren't right and they're missing adjusters . . .
 

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Carb parts

If no luck on this site for your carb parts, head over to the 305 Discussion Forum and look up Ed Moore aka “LOUDMOUSE”. PM him with your search needs. He’s very knowledgeable on the 60’s Honda line, a generous man with time and resources.
 

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Discussion Starter #19
How many chains . . . ?!

Thanks Mike. That was the first place I posted details of the carb issue. I didn't have much luck, but to be fair to the handful of folks who are still active over there, they're fighting a losing battle with spam bots. From what I gather, the forum owner has gone AWOL or just can't be bothered to put mechanisms in place to protect it from junk, and as you'll know if you've been there recently, it's real hard to see the wood for the trees.

As for the carb problem, I've found a way to fix it for now. I intend to write a longer, illustrated post about how to move forward if you find yourself in the same position I did, but essentially the throttle adjusters were missing from the carb tops. That wouldn't be so much of a drama if the tops were standard, but a PO had swapped them out for caps that absolutely no-one anywhere recognises or supplies bits for. I tried everywhere - even the manufacturers and carb specialists, but kept coming up blank. So in the end I drilled and tapped my own holes, fitted standard size adjusters and backfilled the original holes with lead/tin solder. Not the prettiest, but they function fine.

Today's dilemma is what to do about the chains - particularly the primary and oil filter chains. Talking to a couple of chain suppliers over here, there's very few - if any - places that can supply the primary chains. It seems the pitch is imperial (3/8ths) and it's almost certain they were specially made by Honda. So unless I can find somewhere that stocks enough for me to buy several bikes' worth, I may have to find other options. The oil filter chain is a similarly weird size and again, almost impossible to source in the UK. The one place that folks over here have used in the past - SprocketsUnlimited - are pretty much out of their supplies and they won't be getting any more in.

So what do you 'merican (or rest of the world) folks do when it comes to replacing the chains? I don't recall seeing any turn up on eBay (at least, not new) so do you basically find used ones and hope they're OK, or do you have any leads on where I can get something to work with? Alternatively, has anyone tried the Cappellini duplex chain modification and if so, how did it work out? It's expensive, but I get the feeling my options are now very, very limited.
 
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