Author Topic: Keep telling yourself - a restored 750 K2 is an investment  (Read 38532 times)

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Offline HondaMan

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Re: Keep telling yourself - a restored 750 K2 is an investment
« Reply #50 on: September 09, 2008, 06:19:36 PM »
Here's a typical 750 installation, with the "cheesy bracket" option. Fancier cases are also available, if you want a custom unit or a built-in KILL switch for security reasons. The best part: if you ever find a way to fry the electronics (no one has, yet), you just unplug it and plug the points back in, ride home, and complain to me.
See SOHC4shop@gmail.com for info about the gadgets I make for these bikes.

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Blood is thicker than water, but motor oil is thicker yet...so, don't mess with my SOHC4, or I might have to hurt you.
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Offline the-chauffeur

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Re: Keep telling yourself - a restored 750 K2 is an investment
« Reply #51 on: September 10, 2008, 03:27:11 AM »

Hey - that's w-a-y cool.  I'll have to have a long, hard think about one of those once . . .

 . . . Jesus, why does this have to be so bloody difficult?  There's me thinking it'll simply be a case of pulling off the Newtronic light unit and putting the points unit in, but no.  I can't quite believe this, but I can't get the 10mm nut off the end of the auto advance shaft. 

The shaft turns with the nut.  I thought about driving something into the end of the shaft to act as a pin or lock of some sort, but the nut's recessed - so if I do that, I can't get to the sides of the nut to turn it. 

Nothing else moves, but unless I can find some way of stopping the shaft moving, I think I'm screwed. 


Help.  Please.

Offline HondaMan

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Re: Keep telling yourself - a restored 750 K2 is an investment
« Reply #52 on: September 10, 2008, 05:21:27 AM »

Hey - that's w-a-y cool.  I'll have to have a long, hard think about one of those once . . .

 . . . Jesus, why does this have to be so bloody difficult?  There's me thinking it'll simply be a case of pulling off the Newtronic light unit and putting the points unit in, but no.  I can't quite believe this, but I can't get the 10mm nut off the end of the auto advance shaft. 

The shaft turns with the nut.  I thought about driving something into the end of the shaft to act as a pin or lock of some sort, but the nut's recessed - so if I do that, I can't get to the sides of the nut to turn it. 

Nothing else moves, but unless I can find some way of stopping the shaft moving, I think I'm screwed. 


Help.  Please.

Hmmm...this part should be simple, so it makes me wonder if the Newtronics device changed some of the Honda hardware (the Dyna setup does something like that). The stock setup is: a large, flat, thin nut with a recessed center fits on the end of the shaft, and it has a long slot on the back side that engages the end of the spark advancer, to hold it in place. (The spark advancer has its own pin on the crankshaft side, to lock it to the crankshaft in the proper timing spot.) You would normally then hold the big nut with a 23mm(?) wrench, and use a 10mm socket to loosen the inner nut. Then the large nut and a lockwasher come off, and the points plate just slides over the shaft, off and on. I'll try to get a picture of this tonite, on the one in the garage. Can you post a pix of yours? I suspect something is missing, like maybe the big, slotted, recessed nut?
See SOHC4shop@gmail.com for info about the gadgets I make for these bikes.

The demons are repulsed when a man does good. Use that.
Blood is thicker than water, but motor oil is thicker yet...so, don't mess with my SOHC4, or I might have to hurt you.
Hondaman's creed: "Bikers are family. Treat them accordingly."

Link to Hondaman Ignition: http://forums.sohc4.net/index.php?topic=67543.0

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Offline the-chauffeur

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Re: Keep telling yourself - a restored 750 K2 is an investment
« Reply #53 on: September 10, 2008, 05:59:54 AM »

Oh yeah - sorry - should've thought of that . . .

Here are a couple of images; apologies for the quality, but I don't have a decent macro lens to get particularly good close-ups.  Also the flash doesn't help.

Face on


Jaunty angle


Auto advance


As you can see, I've removed the light assembly from the Newtronic plate so that I can get a better view of what's going on.  From looking at the Newtronic instructions, it seems that there may be a bit missing (a plastic cap from the end of the auto advance unit) but it doesn't seem particularly consequential - and I can't tell whether it gets re-attached as part of the plate-fitting process, so it may still be in there.  I tried the method of holding the recessed nut and turning the inner, but as I said, the inner (and shaft) just spins.  I have a bad feeling that a PO has used thread lock or similar on the 10mm nut.

Thanks again for the help.  Any and all gratefully received.



Arse.

Offline HondaMan

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Re: Keep telling yourself - a restored 750 K2 is an investment
« Reply #54 on: September 10, 2008, 05:59:16 PM »
Another Hmmm...there are some upright fingers, or 'ears' under that big nut, if the spark advancer has not been sheared or ground off, for some reason. This is the device that holds the big nut still while turning the little one. If this was previously modified (i.e., the ears ground away for some reason), then the crankshaft could turn with the little nut. That would be unusual, though...

What to try next: put the bike in gear, like 3rd gear, and put a long piece of wood thru the rear spokes to hold the engine still. Then try removing that little nut. In the end, if the little shaft it is on ends up broken, it can be replaced, but it's kind of a pain. It's pressed into the end of the crank, then a little O-ring is used to lock it in there. Pulling out a broken one is difficult, but can be done, eventually. Or, you can weld the shaft back on...

Try getting some of the Loctite Dissolver, as it's called here: it's a solvent for users who overdid the Loctite before you. It may help loosen it up a bit.
See SOHC4shop@gmail.com for info about the gadgets I make for these bikes.

The demons are repulsed when a man does good. Use that.
Blood is thicker than water, but motor oil is thicker yet...so, don't mess with my SOHC4, or I might have to hurt you.
Hondaman's creed: "Bikers are family. Treat them accordingly."

Link to Hondaman Ignition: http://forums.sohc4.net/index.php?topic=67543.0

Link to My CB750 Book: https://www.lulu.com/search?adult_audience_rating=00&page=1&pageSize=10&q=my+cb750+book

Link to website: www.SOHC4shop.com

Offline the-chauffeur

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Re: Keep telling yourself - a restored 750 K2 is an investment
« Reply #55 on: September 11, 2008, 03:09:27 AM »
Uh, sadly no - the bike being in gear makes no difference to the little nut.

I'm guessing the ears are still on the large nut, 'cos it turns/turns with the crank.  No issues there.

But on much closer inspection, it's not the shaft that turns - it stays still, which is something of a relief.  Wierdly, it's the 10mm nut that's the issue - it just turns on the shaft, but neither tightens nor loosens.  It's almost as though there's a circlip or something holding it in place.  Clearly there isn't . . . there's no room for one, but that's the same effect.

Still thinking . . .
« Last Edit: September 11, 2008, 03:32:06 AM by the-chauffeur »

Offline HondaMan

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Re: Keep telling yourself - a restored 750 K2 is an investment
« Reply #56 on: September 11, 2008, 05:44:54 AM »
Uh, sadly no - the bike being in gear makes no difference to the little nut.

I'm guessing the ears are still on the large nut, 'cos it turns/turns with the crank.  No issues there.

But on much closer inspection, it's not the shaft that turns - it stays still, which is something of a relief.  Wierdly, it's the 10mm nut that's the issue - it just turns on the shaft, but neither tightens nor loosens.  It's almost as though there's a circlip or something holding it in place.  Clearly there isn't . . . there's no room for one, but that's the same effect.

Still thinking . . .

"Ah", said Sherlock, "Watson, get your revolver. The mystery is clearing."...
Someone has overtightened the nut and stripped it, or removed the washers behind it and tightened it down past the threads, so it's stuck behind the threads (it's a little too blurry to tell for sure...). This is a little tougher. Can you grip the nut with needle-nose pliers and try to get it to start out of the hole? Otherwise, it's going to be hard to cut it out of there, since the big one is in the way. With a Dremel motor tool, you could just barely get in there with a small cutoff wheel and slice off one side of that nut, then another slice 180 degrees across from it, then it would fall out in 3 or 4 pieces. We'll have to check out the threads on the shaft afterward, to make sure they aren't torn.

After removing it, you may find some damaged threads at the inner end: no to worry, though. Add a flat washer and the lock washer, and the new nut can grip the outer threads and it will hold fine.
See SOHC4shop@gmail.com for info about the gadgets I make for these bikes.

The demons are repulsed when a man does good. Use that.
Blood is thicker than water, but motor oil is thicker yet...so, don't mess with my SOHC4, or I might have to hurt you.
Hondaman's creed: "Bikers are family. Treat them accordingly."

Link to Hondaman Ignition: http://forums.sohc4.net/index.php?topic=67543.0

Link to My CB750 Book: https://www.lulu.com/search?adult_audience_rating=00&page=1&pageSize=10&q=my+cb750+book

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Offline the-chauffeur

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Re: Keep telling yourself - a restored 750 K2 is an investment
« Reply #57 on: September 11, 2008, 09:45:45 AM »

"The game's afoot . . ."
"Three feet?"
"A yard . . ."
- "Scotland Yard" -

You sir, were right.  The thread was "stripped" is one way of putting it.

By the time I'd read your post, I'd pretty much concluded that the only way forward was to get a bit brutal.  Accepting the fact that some kind of cutting was going to be involved, I nipped out to see Dave the Shop and get my order in for what Honda obscurely refer to as Washer, Special - yeah, the nut shaped washer.  They're not cheap, are they?

Got home and after walking round the bike three or four times, thought I'd start small and get more aggressive as necessary.  So after reaching for a centre punch and fine adjusting tool, I put a couple of dents into opposing sides of the small nut.  Got myself a drill and a decent quality small-ish bit and, using the dents as guides, drilled out holes in the faces of the nut.  This allowed me to get the punch in and snap the nut in half.  I have to say that I surprised myself at how delicate the holes were and that I managed to remove the nut without damaging any of the other bits - particularly the shaft.  Turns out that the nut was being held on by the swarf of the part of the thread that had stripped.  Horrible.  Needless to say I've re-cut the thread, which has cleaned up quite nicely.

Sadly, my excitement was short lived.  Having extracted the remaining parts from the shaft, I had a look at the advance unit.  I was right earlier when I said that the Newtronic instructions mentioned something about removing a cap - it's the ridged cylinder that fits onto the advancer and opens the points when the crank spins.  The Newtronic replacement doesn't need the ridges, so there aren't any on the plastic replacement cap.  Sorry if that's a bit long-winded, but it's all leading up to the payoff of me needing to go back and see Dave to cancel the strange washer thingie ('cos I'd not damaged mine) and to ask him to get an advance unit ridged cylinder thingie in for me in its place.   It's at this point I discover that that cylinder isn't sold separately - it's part of the advance unit.  Which is now an obsolete part.  Yup, discontinued.  Craptacular. 

So I'm back to holding my breath again - I've found a used advance unit on fleaBay, but it looks real scruffy.  It'll take another few days to get here . . . just a case of more waiting and seeing I guess.

On the upside, just about everything else is ready to go (he says bravely again).  That'll change when the centre stand comes back from the powdercoaters - didn't realise the exhaust is gonna have to come off to fit that.  Bugger.

Thanks again for the support. 

Offline HondaMan

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Re: Keep telling yourself - a restored 750 K2 is an investment
« Reply #58 on: September 12, 2008, 10:15:13 AM »
Glad to help!
You'll probably still need the nut, but mine has always just had the 6mm nut, a flat washer, and the lock washer. It was the K4 and later that came out with the nut & washer in one piece, which sounds like your description.

When you get the advancer, be sure to mark the position of the points cam (that's the cylinder you describe), because it is possible to remove and reinstall it on the advancer 180 degrees out, so the bike won't run. And, it's possible that someone might have done this for you, before you bought that gizmo...  :-\  Also, the K0-K1 units were exactly this way: 180 degrees out. To swap them, you just remove the cam and turn it and reinstall it, just in case yours is one of the "other year" models. (Something to keep in mind...)  After marking is, disassemble and clean the old, stiff grease out of the inside, lightly regrease and reassemble. I'd recommend doing the same to the weights on their pivots, and mind the little spacers and 'gee-whiz-where'd-they-go?" clips  ;D  on those pivots.

You can test this cam timing thing by installing the advancer and the points plate, set the 1-4 points to .014" on the high side of this cam, then connect an ohmmeter across the points and turn the engine forward (with the big bolt) until the points just open again. Look in and see if it is close to the 1-4 marks. If so, everything is cool, otherwise, it's cam-flipping time.
See SOHC4shop@gmail.com for info about the gadgets I make for these bikes.

The demons are repulsed when a man does good. Use that.
Blood is thicker than water, but motor oil is thicker yet...so, don't mess with my SOHC4, or I might have to hurt you.
Hondaman's creed: "Bikers are family. Treat them accordingly."

Link to Hondaman Ignition: http://forums.sohc4.net/index.php?topic=67543.0

Link to My CB750 Book: https://www.lulu.com/search?adult_audience_rating=00&page=1&pageSize=10&q=my+cb750+book

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Offline the-chauffeur

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Re: Keep telling yourself - a restored 750 K2 is an investment
« Reply #59 on: September 13, 2008, 03:40:34 PM »
I think I'm within touching distance . . . although I have to say, I was slightly thrown by the difference in design between the K2 and K4 auto advance mechanism.  Thanks for the heads up on that.

I've rebuilt the K2 mechanism for the bike and bolted it, and the new points assembly, into the engine housing.  I then tried (and obviously failed) to gap the breakers, or get the timing right, or both.  I got the spacing right according to all of the manuals, but it seems that no matter what I did, I couldn't get a spark.  I even tried turning the cylinder through 180deg, but no joy.

I'm beginning to wonder whether there might not be enough juice in the battery to get the coils to fire - the battery is getting on, and having rewired the lights to sidelight always on, could it be that either I need a new battery, or that I've somehow knackered the coils? 

Fortunately I live within two miles of a very good (and understanding) Honda dealer, so if all else fails, I can push the bike there and get them to recommission it.


Oh - one last thing before I forget; the part of the fiche that shows the coils (basically the loom diagram) also shows a buzzer of some sort that sits under the coils.  I'm sure I should know this, but what the hell's that for?  Is it some kind of turning alarm?
« Last Edit: September 13, 2008, 03:48:40 PM by the-chauffeur »

Offline HondaMan

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Re: Keep telling yourself - a restored 750 K2 is an investment
« Reply #60 on: September 13, 2008, 08:54:34 PM »
I think I'm within touching distance . . . although I have to say, I was slightly thrown by the difference in design between the K2 and K4 auto advance mechanism.  Thanks for the heads up on that.

I've rebuilt the K2 mechanism for the bike and bolted it, and the new points assembly, into the engine housing.  I then tried (and obviously failed) to gap the breakers, or get the timing right, or both.  I got the spacing right according to all of the manuals, but it seems that no matter what I did, I couldn't get a spark.  I even tried turning the cylinder through 180deg, but no joy.

I'm beginning to wonder whether there might not be enough juice in the battery to get the coils to fire - the battery is getting on, and having rewired the lights to sidelight always on, could it be that either I need a new battery, or that I've somehow knackered the coils? 

Fortunately I live within two miles of a very good (and understanding) Honda dealer, so if all else fails, I can push the bike there and get them to recommission it.


Oh - one last thing before I forget; the part of the fiche that shows the coils (basically the loom diagram) also shows a buzzer of some sort that sits under the coils.  I'm sure I should know this, but what the hell's that for?  Is it some kind of turning alarm?

Stick a multimeter on the battery, see if it's got at least 10 volts left in it: that's enough to fire the coils. The battery plates will have a white, mouldy look to them if they got sulphated from being dead too long. A battery charger should be enough to let you check out the timing, at least. Lay a sparkplug against the head, plugged to the coil, to watch for the spark. It should be a tiny blue, quick spark, if the battery is low.

One thing that may happen: new points come with a coating of cosmolene, which insulates them against rust and, unfortunately, electricity. Clean the contacts with alcohol (some stronger than Stout, though...) or naptha or such, then you can test the system by manually opening and closing the points. Use an insulated screwdriver to do this, or you'll get that taser-like sensation for an hour or so...closing the contacts charges the coil, and opening them fires the coil, but check that the points/condensor wiring is not shorted to the ground lug on the points at the little bolts: this can happen if the connectors are slid on in the wrong direction (then they tend to wrap around the edge of the mounting bracket and touch it, permanently grounding the coils).

Also check: the KILL switch and its circuit. This consists, on the K2, of a black wire that connects with the others in the headlight (this is IGNITION circuit), goes up to the KILL switch on the right handlebar, where it becomes a black-white wire and returns to the headlight. There, it plugs into another black-white wire that goes to the (+) side of the coils, as 2 female sockets, right above the coils. The coils' (-) sides then have a yellow and blue wire, which should go back into the harness and reappear under the seat, go down by the right rear side of the engine, where they plug into the same yellow and blue colors from the points plate. That's their whole circuit.

You can turn on those coils and leave them on all day, and it won't hurt them. But, they will drain the battery in about 15 minutes if left on.

That electrical thingie you're describing: it's a turn signal beeper. It physically resides on the inside of the left headlight ear, where there is a square hole to mount it's rubber case. The Honda fische just show it in a poor perspective. If it were under the tank, you'd never hear it. On the K2/K3, there is also a small button under the left horn button on the left handlebar: pushing this button in will shut that stupid beeper up at intersections, when everyone is staring at you...but, it is safer when you're buzzing down the road, and forgot to turn off the blinkers. It helps prevent confusing everyone around you about where you plan to turn next.  ::)
See SOHC4shop@gmail.com for info about the gadgets I make for these bikes.

The demons are repulsed when a man does good. Use that.
Blood is thicker than water, but motor oil is thicker yet...so, don't mess with my SOHC4, or I might have to hurt you.
Hondaman's creed: "Bikers are family. Treat them accordingly."

Link to Hondaman Ignition: http://forums.sohc4.net/index.php?topic=67543.0

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Offline Hush

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Re: Keep telling yourself - a restored 750 K2 is an investment
« Reply #61 on: September 13, 2008, 09:29:14 PM »
We don't have those beeper things in New Zealand either Chauf, amazing reconstruct, sorry about all the hassels you have run into.
It will all be worth it when she runs.
I think the thing I most like about motorcycling is the speed at which my brain must process information at to avoid the numb skulls who are eating pies, playing the ukulele, applying make-up etc in the comfort of their airconditioned armchairs as they make random attempts to kill me!!!!!!!

Offline the-chauffeur

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Re: Keep telling yourself - a restored 750 K2 is an investment
« Reply #62 on: September 14, 2008, 08:11:49 AM »
Thanks Hush.  I'm OK with the mechanical bits ('cos you can generally see whether they fit together/work) but find electrics a bit baffling -  I really need to go back to school and do some kind of course on using a multimeter.  Checking continuity I can do.  Much beyond that, I get lost very quickly.

Well, it's not the battery.  I know 'cos, stupidly or otherwise, I bought a new one.  I kinda forgot to mention something earlier in the build story, which'll probably explain the buying decision (kinda).  After reassembling the engine with all the bolts tightened to the correct torque settings, the crank wouldn't turn.  So we backed off the crank bolts and hey presto! it turned nice and freely.  The conclusion we drew was that although we'd put lubricant on the shells, they'd probably benefit from being soaked in oil before the bolts were retightened.  So we filled the cases with oil, turned the engine over several times and that's pretty much how it's been stood since the engine went back into the frame.

Fast-forward to yesterday, and re-torquing the bolts is one of my 'to-do' list jobs.  The day for crossing off the small remaining jobs arrives, and I got the torque wrench out.  Everything was torqued up and guess what?  Press the starter and the electrics go 'click' - no turnover. Click again, no turnover.  Now I've had this happen to me before on other bikes and it almost always means that there isn't enough cranking power in the battery; add that to my suspicions about the lack of juice to fire the coils and that should explain why I bought a new battery.

Only to find that it wasn't the battery.  Nope.  Backed off the crank bolts a bit and over it turns.  Knickers.  Ah well, I now have a spare battery . . . And did I mention the refitting-the-tank-with-the-fuel-tap-sitting-on-the-carbs saga?  On and off and on again.

Back to the ignition system.

I ran through all of the checks you've suggested - twice.  You may recall I rewired the kill switch a week or so ago and so I was conscious that it could be a weak point.  Turns out that it's fine; continuity between black and black-white leads when in the 'on' position, no continuity when 'off'.  That's good, no?  At the same time, there's continuity between the black-white lead in the headshell and the connector to the coils.

Turning swiftly to the new points plate, I thought I'd have a go at checking continuity between the contact breakers - I'm hoping the clue is in the name and that when open, there shouldn't be a reading.  Well, I couldn't find any two points on the breakers that I couldn't get a continuity reading from - regardless of whether the points were open or closed (which, incidentally I had cleaned with nail varnish remover).  That strikes me as being wrong, but I can't see any badly fitted connections or anything particularly untoward - although I'm not entirely sure what I need to be looking for.

Dunno whether it's gonna help, but here's a photo:



You'll see that I've replaced the adjusting screws with hex heads - I can't be doing with crossheads.  It's got to be here somewhere . . .


 
« Last Edit: September 14, 2008, 08:24:44 AM by the-chauffeur »

Offline 754

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Re: Keep telling yourself - a restored 750 K2 is an investment
« Reply #63 on: September 14, 2008, 08:44:51 AM »
Sometghing sounds wrong on your main bearings. If you backed of the bolts to turn it, something is not right.  Better to deal with it now, it could get more expensive after you run (ruin) it.

Did you use plastiguage on the bearings, before you assembled?
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Offline HondaMan

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Re: Keep telling yourself - a restored 750 K2 is an investment
« Reply #64 on: September 14, 2008, 09:15:26 AM »
Sometghing sounds wrong on your main bearings. If you backed of the bolts to turn it, something is not right.  Better to deal with it now, it could get more expensive after you run (ruin) it.

Did you use plastiguage on the bearings, before you assembled?

Yeah, what he said...that sounds very serious.
First, the electrics: the picture tells it all. There is no place where BOTH points are open at the same time on these points cams, so I suspect that the instructions you had were not correct. It goes like this:
1. Turn the engine until the 1-4 mark is visible in the window, then go about 1/8 turn further. This puts the points on their high point on the cam.
2. Now, set the gap on the 1-4 points at .014".
3. Next, turn the crank until the 2-3 marks appear in the window, then 1/8 turn more.
4. Set the 2-3 points at .014".
5. Now, this should be enough to make the engine run, at least, if ragged. If you have a timing light, the rest goes like this: slightly loosen the plate screws, connect the timing light to spark wire 1 or 4, start the engine, and turn the plate until the 1-4 mark for "F" is lined up in the window. Run up to 2500 RPM, and the advance marks should then appear, next to the indicator mark. Tighten down the palte screws and check timing once more, in case it moved a bit.
6. Repeat step 5, but for the 2-3 points and plug wire, and adjust the little baseplate only for the 2-3 points.

Steps 5 and 6 can also be done with a little lite bulb, like one from the 'dashboard' on the handlebars, or a 12 volts troubleshooting light: for this, you connect one side of the bulb to the little bolt where the wires connect to the points, the other to the engine case, and turn on the ignition key and KILL switch to RUN. Then, slowly turn the engine over (by that big bolt) until it's near the 1-4 "F" mark, and the light should come on at that mark. Turn the whole points plate back or forth until this is right on that mark. Repeat for the other points, using the 2-3 "F" mark. This method is called 'static timing', or 'roadside setup'.

About that crankshaft: with all bolts torqued, it will turn easily, if everything is correct. It sounds like one (or more?) of the bearings has turned in the journals. This can happen if the lower case is bumped too hard during the time when you are closing the cases: the bearing can come loose, and it misaligns at the little locating edge that's supposed to hold it in position. If you start the engine like this, it will destroy the crankshaft in seconds! Better check that now, before it gets expensive...  :-\
See SOHC4shop@gmail.com for info about the gadgets I make for these bikes.

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Blood is thicker than water, but motor oil is thicker yet...so, don't mess with my SOHC4, or I might have to hurt you.
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Link to Hondaman Ignition: http://forums.sohc4.net/index.php?topic=67543.0

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Offline the-chauffeur

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Re: Keep telling yourself - a restored 750 K2 is an investment
« Reply #65 on: September 14, 2008, 12:32:15 PM »

Oh.  Fork.


Or something.


Well, that's not the best news I've ever had, but thanks for saving me from a whole world of hurt later on.  If I said what is Plastiguage, would that answer your question?

So the engine's gotta come out again - that's something I could really do without, but if that's the way it's gotta be, I'm not gonna waste any time shouting and swearing about it. 

Down to business.  To sort this out, am I gonna need to disassemble the whole engine top-to-bottom again (I'm praying not) or can I turn the engine upside down as a unit and just remove the lower crankcase with the crank and other bits left in the top half?

Looks like this will take somewhat longer than I was hoping . . .

Offline 754

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Re: Keep telling yourself - a restored 750 K2 is an investment
« Reply #66 on: September 14, 2008, 01:13:42 PM »
yup, , remove shifter cover and a few parts in there, dyno and clutch cover, then turn over and split cases..remember a few bolts on the topside (one by the starter).

Plastiguage is a thin plastic wire that is installed on the crank before tightening the case or rod caps, then they are torqued.. Then without turning it over you disassemble and compared the width of the flattened strip of plastic to the guage on the package.. telling you the actual clearance.

Used for checking wear of bearings and clearance of new ones. The shells are selected by a letter/number code which is marked on the crankcase and crank.
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Offline HondaMan

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Re: Keep telling yourself - a restored 750 K2 is an investment
« Reply #67 on: September 14, 2008, 09:19:07 PM »
yup, , remove shifter cover and a few parts in there, dyno and clutch cover, then turn over and split cases..remember a few bolts on the topside (one by the starter).

Plastiguage is a thin plastic wire that is installed on the crank before tightening the case or rod caps, then they are torqued.. Then without turning it over you disassemble and compared the width of the flattened strip of plastic to the guage on the package.. telling you the actual clearance.

Used for checking wear of bearings and clearance of new ones. The shells are selected by a letter/number code which is marked on the crankcase and crank.

If this process seems a mystery, send me an e-mail at my home address. I'll send you some pix I recently made of this process, for the book on 'how to rebuild the 750' that I'm making... home: mgparis@concentric.net . The pix are too big to post here, it makes a BIG post...
See SOHC4shop@gmail.com for info about the gadgets I make for these bikes.

The demons are repulsed when a man does good. Use that.
Blood is thicker than water, but motor oil is thicker yet...so, don't mess with my SOHC4, or I might have to hurt you.
Hondaman's creed: "Bikers are family. Treat them accordingly."

Link to Hondaman Ignition: http://forums.sohc4.net/index.php?topic=67543.0

Link to My CB750 Book: https://www.lulu.com/search?adult_audience_rating=00&page=1&pageSize=10&q=my+cb750+book

Link to website: www.SOHC4shop.com

Offline the-chauffeur

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Re: Keep telling yourself - a restored 750 K2 is an investment
« Reply #68 on: September 15, 2008, 09:48:41 AM »

After the mother of all wrestling matches, the engine came back out of the frame.  Despite having removed as much of the excess weight as possible (starter motor, clutch, side plates and so on), that bloody lump still put up one hell of a fight.  But it's out.

Next problem is the very resistant Hondabond on the mating surfaces.  We did such a good job sealing the cases up when we put 'em back together last time that they now won't separate.  And yes, I've removed all of the top and bottom case bolts, side cases, shifter bits and other things that might get in the way. 

Any advice?  I've already tried rubber mallets/hammers without any success.  I'm wondering if I'm gonna have to buy a crankcase splitter . . .

And the frame's looking very forlorn . . .

Offline HondaMan

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Re: Keep telling yourself - a restored 750 K2 is an investment
« Reply #69 on: September 15, 2008, 06:15:44 PM »

After the mother of all wrestling matches, the engine came back out of the frame.  Despite having removed as much of the excess weight as possible (starter motor, clutch, side plates and so on), that bloody lump still put up one hell of a fight.  But it's out.

Next problem is the very resistant Hondabond on the mating surfaces.  We did such a good job sealing the cases up when we put 'em back together last time that they now won't separate.  And yes, I've removed all of the top and bottom case bolts, side cases, shifter bits and other things that might get in the way. 

Any advice?  I've already tried rubber mallets/hammers without any success.  I'm wondering if I'm gonna have to buy a crankcase splitter . . .

And the frame's looking very forlorn . . .

OK, here's some hot tips on this topic (right from my upcoming book...):
Opening the cases: count your removed bolts - 20 of the 6mm bolts, 13 of the larger 8mm bolts (and 2 nuts, 14 washers in 8mm). If you don't have this many on a K2, there's still one or more in the crankcases. It only takes one to break a case.  :o
The cases clamshell from the rear forward. Best place: take a long screwdriver, and with the engine upside down, pry front the bottom side of the countershaft sprocket and the upper (left) engine-to-frame support. It will take little pressure to release Hondabond #4, and it will gently 'peel' toward the front as the bond breaks. After it's open about 1/2" or so, let it go and try to pull the bottom case straight up: it usually lets go easily now.

After it's open: look for Hondabond in the bearings, especially near the points seal or on the alternator side. When you go to reassemble: think of Hondabond as paint, like house paint, and apply it about that thick: that's all it takes. More than that will make it go many places where it should not be, like bearings and oil pump screens (after startup).

In between disassembly and reassembly: Plastigage each bearing on the crankshaft. Make sure they are wiped clean of oil, the bearing halves are properly seated, and the oil is wiped (carefully, gently, no solvent) from the bearing faces. Lay the GREEN Plastigage (about 3/4" long pieces) straight across the crank journals, in line with the crank axis (all 5 at once is OK), close the cases and retorque the 8mm bolts at the crank. Unbolt and open the cases again (by now, you're good at it!) and compare how far the Plastigage has squished out: the width must be compared to the green bands on the Plastigage's paper wrapper. Less bearing clearance = more squished-out Plastigage width. Anywhere between .0008" and .018" is very good. If less than .0008" (a very wide squish, indeed), the bearing shell is too tight (pretty rare, unless wrong shells were selected in a rebuild). More than .0022" is pretty loose (no squish at all, basically), but is still permissible unless you're going racing (.0032" is the upper limit).

Hang in there, we'll talk you through it. The best part: there is nothing 'hidden' in the assembly of these engines, so they are a real confidence-builder, once reassembled properly. And then, they typically last 50,000 miles or more!
See SOHC4shop@gmail.com for info about the gadgets I make for these bikes.

The demons are repulsed when a man does good. Use that.
Blood is thicker than water, but motor oil is thicker yet...so, don't mess with my SOHC4, or I might have to hurt you.
Hondaman's creed: "Bikers are family. Treat them accordingly."

Link to Hondaman Ignition: http://forums.sohc4.net/index.php?topic=67543.0

Link to My CB750 Book: https://www.lulu.com/search?adult_audience_rating=00&page=1&pageSize=10&q=my+cb750+book

Link to website: www.SOHC4shop.com

Offline the-chauffeur

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Re: Keep telling yourself - a restored 750 K2 is an investment
« Reply #70 on: September 16, 2008, 01:52:32 AM »

When in doubt, get some sleep.

Having read your helpful posts and whilst wiping my blurry eyes, I counted the case bolts and found I was three light.  Checked the diagrams again and compared them with the cases, and they were exactly where they're s'posed to be.  Once they had come out, the halves came apart quite easily.  What's that . . . over-confidence comes before a huge screw up?  Yeah.  Thanks for bearing with me.

As I pulled the bottom case away, it was clear that one of the bearing shells (or are the bits that sit in the lower case called journals?) had come away from the lower case and was floating about on the bearing.  My guess is that it's been like that since we closed them up last time, and bearing in mind that they weren't changed (so the tolerances should be the same) when I stripped the engine, the little lip on the side is probably what's been stopping the crank turning when the bolts are tightened.  I'm on my way out to see if I can find some plastigauge stuff, but we're a bit light on decent parts places round here, so I'm not holding my breath.

More paranoia.  When I rotate the crank through half a turn or so, something in the top end clicks.  It's quite a pronounced click and only seems to happen when the crank is rotated in one direction.  It doesn't happen every time, and the slower the turn, the less it happens.   I think it's coming from the top end (either pistons or head unit), but it's very hard to isolate.  When we put the engine together last time, we did so in stages, so I have no idea if this is right or not.  Moreover, I removed the camchain tensioner when I pulled the engine out (primarily to get at the starter motor) so again, I dunno if this has anything to do with it.  Any suggestions on that front?

Big sigh . . .

Offline HondaMan

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Re: Keep telling yourself - a restored 750 K2 is an investment
« Reply #71 on: September 16, 2008, 05:42:40 AM »
Umm...if the camchain is not yet adjusted, i.e., has slack in it, there can be some noises coming from it when the crank is turned. This can't be tested until you tighten up that chain, though, which can't happen properly until this bottom end is back together. So, let's wait a bit on that one...when the bottom case is back on, turn the engine right-side up and set the camchain tension, then check for the noise again.

If you didn't change any bearing shells, then you're probably right about the clearances. They last a LONG time, if they don't show any scratches or burn marks in them, and with a 5-main-bearing bottom end, they are forgiving if just one is out of specs and worn. It's one of the most robust bottom ends found in bikedom! If you always run 20w50 oil, they can last 100,000 miles.

First, another tip, then a question: to make your life easier during installation of the motor (and any future removals), take a look at the bottom loop of the frame, right hand side. On that mount where the lower (long) bolt goes through the whole frame-engine combo, you'll see a flange on the inside of that mount. (At this point, you'll probably see corresponding gouges on the bottom of the engine cases from it!) Take a file or grinder, and grind off the top edge of that flange, down to the diameter of the mount itself. touch it up with a bit of paint to keep the rust away. You will be amazed at how much easier the engine goes back in - or comes out, if there's a next time. Always keep the engine parallel to the frame during these excursions, and your life will be far easier: the front of the engine lifts up a little to go over this mount, and to clear the exhaust nipples (yup, that's what they're called here) on the way in and out, and a little bit of rear-in-first-an-inch, then-front action will smoothly wiggle it in.

The question: why did you remove the starter? There's no need for this, and it means you must also remove the alternator cover now to put the shaft and gears back together inside there...  ???
See SOHC4shop@gmail.com for info about the gadgets I make for these bikes.

The demons are repulsed when a man does good. Use that.
Blood is thicker than water, but motor oil is thicker yet...so, don't mess with my SOHC4, or I might have to hurt you.
Hondaman's creed: "Bikers are family. Treat them accordingly."

Link to Hondaman Ignition: http://forums.sohc4.net/index.php?topic=67543.0

Link to My CB750 Book: https://www.lulu.com/search?adult_audience_rating=00&page=1&pageSize=10&q=my+cb750+book

Link to website: www.SOHC4shop.com

Offline the-chauffeur

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Re: Keep telling yourself - a restored 750 K2 is an investment
« Reply #72 on: September 16, 2008, 06:17:45 AM »
Why did I remove the starter?  Excess weight.  No other reason, really.  And I've got all the other sidecovers off anyway.  I'm not so worried about the alternator bit - been there, done that.  Thanks for the pointer on the frame.  I think for now I'll struggle through 'cos I don't really wanna mess up the powdercoat.  I'll just get a few more pairs of hands when putting it back in the frame.

OK.  I was right about Plastigauge . . . it's not been seen 'round these parts in a good long while.  None of the motor factors or engine shops in a fifteen mile radius have seen it, used it, or stocked it in years.  Someone managed to find me a very small piece of red stuff, but I gather that's not really very helpful.  Given that the shells are the same, I think I'm gonna leave that for now.

Thanks for the reassurance on the bearing front - that's really good to know.  So back to the bits.  There's nothing untoward inside the cases or on the bearings - no scratches, scoring or other goings on that suggest anything's outta place.  In fact, they're clean as a whistle considering their age. 

Now, what exactly constitutes "should turn freely" in relation to the crank when mounted and torqued?  Remembering that the head is on, and the pistons and valves are in, am I right in thinking that "freely" is a figure of speech?  It's a big old bugger, and whilst I can get the crank to turn with a socket on a bar, freely is not a word I'd use.  Well, perhaps it is to describe the lack of any noises, or feelings/sense of grating or grinding when it turns - but it needs a fair old hoofing to get it to go.  With the bottom of the case off, the crank moves with relatively little effort (again, the word is relatively - that's not no effort at all; more a reasonable amount of push).  I've had the lower case on and off several times now, and get the same result each time I tighten the crank bolts - it gets progressively harder to move the more bolts get tightened, but never to the point where it won't move.  And crucially, no movement, or new marking or scoring in the bearings.

I can't imagine that this is wrong, but since I don't know what right is, I'm struggling a bit to know whether to do it all up again.  Guessing again, but if anything bearing-wise was out of true, it would show up either in scoring marks or lubricant trails after the engine's been turned.  Unless I've missed something blindingly obvious, I think I'm probably gonna take a punt on it and go with it as is - reassembled very carefully of course.
« Last Edit: September 16, 2008, 06:42:51 AM by the-chauffeur »

Offline bryanj

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Re: Keep telling yourself - a restored 750 K2 is an investment
« Reply #73 on: September 16, 2008, 06:53:18 AM »
You can still get plastigauge, but probably by post.

(1) DO NOT oil the back opf the shells/crankcase

(2) if you sent it away with the shells in they do fall out and may have been put in the wrong places---Having said thateven with the tightest shells it should turn over
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Offline the-chauffeur

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Re: Keep telling yourself - a restored 750 K2 is an investment
« Reply #74 on: September 16, 2008, 07:12:09 AM »
Hey Bry

Have no fear - there's no oil on the rear of the shells.  AFAIK they didn't fall out during cleaning (although it's possible).  Looks to me like one came loose during reassembly, but having put that back, everything's as it was when the engine was dismantled.

Like I said, each time I tighten the crank bolts turning it over gets progressively harder, but never to the point where it won't move at all.  I assume that over-tightening will ultimately prevent any movement whatsoever, so I'm avoiding that.  But again, I'm struggling with just how hard a job it should be.