Author Topic: 1972 CB750 Four K2 -- Rebuilt to NEW OLD STOCK -- PIX ON PAGE 50  (Read 265964 times)

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Offline Terry in Australia

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Re: 1972 CB750 Four K2 -- Project "Ice Cream"-- ENGINE TEARDOWN
« Reply #200 on: January 03, 2014, 03:10:50 PM »
No worries Ed, if you've got room in your basement/shop, an old oven is a handy tool for not only dropping sleeves, but also for curing engine paint, loosening valve guides, curing powder coating etc. I bought a small one on eBay for 2 bucks and used it until I scored an industrial oven which has much more room.

Be careful with the sanding, even with a wide block it's easy to "round" the gasket surfaces, that's why I use the strip disc, it's fast and only removes the old gasket, and not the aluminum. Don't bother with fine abrasive paper, all you'll do is polish the old gasket. Cheers, Terry. ;D 
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Offline edwardmorris

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Re: 1972 CB750 Four K2 -- Project "Ice Cream"-- ENGINE TEARDOWN
« Reply #201 on: January 03, 2014, 05:51:00 PM »
No worries Ed, if you've got room in your basement/shop, an old oven is a handy tool for not only dropping sleeves, but also for curing engine paint, loosening valve guides, curing powder coating etc. I bought a small one on eBay for 2 bucks and used it until I scored an industrial oven which has much more room.

Be careful with the sanding, even with a wide block it's easy to "round" the gasket surfaces, that's why I use the strip disc, it's fast and only removes the old gasket, and not the aluminum. Don't bother with fine abrasive paper, all you'll do is polish the old gasket. Cheers, Terry. ;D
I'll keep an eye out for an oven on craig's list. I've done inspection passing electrical work around the house but never messed with gas lines so a little apprehensive about that. I can have someone install it for me though if I really need it.

As for the gasket, I picked up some acetone and I had some 1000 grit sand paper at home. First round, wet the surface with acetone and scraped it off with a credit card. Then for the really stuck crap, I just wet sanded with the 1000g and wetting with acetone itself. Made my life easier and it looks pretty clean now. I'll post some pix after dinner tonight.

I did look at the strip disc, looked a bit too coarse so didn't try it yet.

Offline edwardmorris

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Re: 1972 CB750 Four K2 -- Project "Ice Cream"-- ENGINE TEARDOWN
« Reply #202 on: January 03, 2014, 10:01:27 PM »
Here they are. I washed it in my poor man's parts washer to get as much of the dirt and crud off from in between the fins. Its going to need a few more rounds of that. I have no idea why I don't have any WD-40 around the house, so I dabbed the sleeves with some motor oil and put it aside for now. Moving on to pistons tomorrow and dive into the crankcase as we're expecting to warm back up to freezing (0C).

Offline Terry in Australia

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Re: 1972 CB750 Four K2 -- Project "Ice Cream"-- ENGINE TEARDOWN
« Reply #203 on: January 04, 2014, 12:18:41 AM »
Those gasket surfaces look great Ed, good job! Yep, lots more work required on the finned areas, but I've no doubt you'll get it squeaky clean too. Cheers, Terry. ;D 
I was feeling sorry for myself because I couldn't afford new bike boots, until I met a man with no legs.

So I said, "Hey mate, you haven't got any bike boots you don't need, do you?"

"Crazy is a very misunderstood term, it's a fine line that some of us can lean over and still keep our balance" (thanks RB550Four)

Offline edwardmorris

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Re: 1972 CB750 Four K2 -- Project "Ice Cream"-- ENGINE TEARDOWN
« Reply #204 on: January 04, 2014, 03:26:16 PM »
Thanks Terry :)

I went through the first step that Hondaman listed on what to look for with the countershaft. From what I can see, all the gears, dogs, slots etc. are in good shape with you nicks, dents or any other obviously visible damage. Shift forks too, look alright. But, I'm the noob, so I'll let the experienced eyes be the judges here. Not the best pics but I can take more at different angles if needed. I've looked as best as I can and I think I'm good here. Only thing I couldn't get out was that damned thing with the roller drum. How does that come off? The neutral switch also hasn't fallen out even with the bolt and plate removed. Is that what is still holding the roller drum in? What to do?

Offline edwardmorris

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Re: 1972 CB750 Four K2 -- Project "Ice Cream"-- ENGINE TEARDOWN
« Reply #205 on: January 04, 2014, 03:27:39 PM »
More

Offline edwardmorris

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Re: 1972 CB750 Four K2 -- Project "Ice Cream"-- ENGINE TEARDOWN
« Reply #206 on: January 04, 2014, 03:30:10 PM »
Last pic is what I want to remove next. Any suggestions on removing the kickstart, oil pump and the roller on this side of the case?

Offline Kickstart

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Re: 1972 CB750 Four K2 -- Project "Ice Cream"-- ENGINE TEARDOWN
« Reply #207 on: January 04, 2014, 05:00:16 PM »
Man... following your thread is making me feel lazy.  Nice effort here.

Yeah, that neutral switch in the bottom needs to come out for the gear drum to slide out.  You may have to pry the neutral switch out a little with a flat head screwdriver. That's what I had to do to get mine out.

The more experienced here will know better, but the gears and dogs look OK to me... but I think you should get some close-up angled shots of the dogs, especially on the 2nd gear dogs (I believe the C5 gear - the one that you had to pull out the side to get the secondary shaft out).

Also try to get some close-up pictures of where the dogs contact on the mating gear (witness marks).

The fork shaft looks like it has some shiny spots... you might want to mic that to see if there is any significant wear... again, others would know better than me.

- Chris
75' CB750F Orange flake (rider)
75' CB750F Blue (Project)
75' CB750F Painted black (Project)
No Reserve Racing #171 AHRMA

Offline edwardmorris

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Re: 1972 CB750 Four K2 -- Project "Ice Cream"-- ENGINE TEARDOWN
« Reply #208 on: January 04, 2014, 06:19:28 PM »
I'll try and take some close ups of those two gears. I didn't take any that way because you basically need a video to see all the teeth. I went through all of them and, to me at least, looks like all the edges are actually sharp with no nicks or dents anywhere. If I should use a mag glass to be sure, then maybe I'll find some. I'll look through again and maybe take pix of the worst spots on their circumference.

Prying the neutral switch out with a screwdriver had failed when I was splitting the cases. There is a rubber gasket that keeps pulling the switch back inside. I know @Terry hates "Chiselers" but I had to resort to Pic 1 ;) the chisel opens at 90deg so I just pushed the damned switch down far enough to get the roller out. Once the roller was out I pushed the switch out by hand.

On to the million dollar mistake, how do I deal with the broken screw in here? Drill it out?

Offline edwardmorris

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Re: 1972 CB750 Four K2 -- Project "Ice Cream"-- ENGINE TEARDOWN
« Reply #209 on: January 04, 2014, 06:24:51 PM »
Oil pump is out, the screen had some crap in it but not too horrific.

Offline edwardmorris

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Re: 1972 CB750 Four K2 -- Project "Ice Cream"-- ENGINE TEARDOWN
« Reply #210 on: January 04, 2014, 06:29:33 PM »
Only thing left in the lower case is the kick start gear assembly. That dowel style pin isn't budging and needlenose pliers aren't gripping it well enough to try and pull it out. Is there an easier way to pull it out?

Offline Kickstart

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Re: 1972 CB750 Four K2 -- Project "Ice Cream"-- ENGINE TEARDOWN
« Reply #211 on: January 04, 2014, 06:39:57 PM »
I'll try and take some close ups of those two gears. I didn't take any that way because you basically need a video to see all the teeth. I went through all of them and, to me at least, looks like all the edges are actually sharp with no nicks or dents anywhere. If I should use a mag glass to be sure, then maybe I'll find some. I'll look through again and maybe take pix of the worst spots on their circumference.

Prying the neutral switch out with a screwdriver had failed when I was splitting the cases. There is a rubber gasket that keeps pulling the switch back inside. I know @Terry hates "Chiselers" but I had to resort to Pic 1 ;) the chisel opens at 90deg so I just pushed the damned switch down far enough to get the roller out. Once the roller was out I pushed the switch out by hand.

On to the million dollar mistake, how do I deal with the broken screw in here? Drill it out?

Sorry... meant to say take pictures of the dogs, not the teeth, on the gears and where they mate up on the other gear.

Regarding that broken screw... that's a tough one.  Maybe try drilling out with a reverse drill bit if you have one, or just take it to a machinist.
Is there anything sticking out to grab onto?  I've never had good luck getting broken bolts out that were broken flush.  Every e-z out I've tried I ended up snapping off in the bolts. 

- Chris
75' CB750F Orange flake (rider)
75' CB750F Blue (Project)
75' CB750F Painted black (Project)
No Reserve Racing #171 AHRMA

Offline Kickstart

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Re: 1972 CB750 Four K2 -- Project "Ice Cream"-- ENGINE TEARDOWN
« Reply #212 on: January 04, 2014, 06:49:06 PM »
Only thing left in the lower case is the kick start gear assembly. That dowel style pin isn't budging and needlenose pliers aren't gripping it well enough to try and pull it out. Is there an easier way to pull it out?
Yes... use a large (8") Diagonal-Cutting Pliers ("Dykes")
Something like this:
http://www.homedepot.com/p/Klein-Tools-8-in-High-Leverage-Diagonal-Cutting-Pliers-D228-8/100020319?N=bm4r#.UsjGSfRDsuc

You grip the pin just enough for the pliers to get a good bite (but not enough to cut the pin) and then slowly push down on the pliers to leverage out the pin. Since the plier head is angled it works nicely as a fulcrum.
- Chris
75' CB750F Orange flake (rider)
75' CB750F Blue (Project)
75' CB750F Painted black (Project)
No Reserve Racing #171 AHRMA

Offline MCRider

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Re: 1972 CB750 Four K2 -- Project "Ice Cream"-- ENGINE TEARDOWN
« Reply #213 on: January 04, 2014, 08:36:08 PM »
Only thing left in the lower case is the kick start gear assembly. That dowel style pin isn't budging and needlenose pliers aren't gripping it well enough to try and pull it out. Is there an easier way to pull it out?
Many threads on this, many have struggled with it. My method is to grab the exposed part of the pin with smallish vice grips, squeezing the pin closed a little. Lever up on the pliar with screwdriver or tire iron. Rinse and repeat until its out.
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Offline edwardmorris

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Re: 1972 CB750 Four K2 -- Project "Ice Cream"-- ENGINE TEARDOWN
« Reply #214 on: January 04, 2014, 08:42:20 PM »
HA, thanks kickstart and Ron, I must have just missed your posts. I ended up searching and found the same suggestion (almost the same words from Ron's earlier posts :) ) and I got it out. With the greatest stroke of luck, the pliers kickstart mentioned were in my cheap 10 for $10 plier set kit. Worked like a charm!

Back to the gears, I hope these are the correct angles.

Offline edwardmorris

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Re: 1972 CB750 Four K2 -- Project "Ice Cream"-- ENGINE TEARDOWN
« Reply #215 on: January 04, 2014, 08:43:28 PM »
and the mating ones

Offline edwardmorris

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Re: 1972 CB750 Four K2 -- Project "Ice Cream"-- ENGINE TEARDOWN
« Reply #216 on: January 04, 2014, 08:45:52 PM »
Before I move on to the other half, visually, how do these look? From Hondaman's book (if I'm reading the book and these bearing right) this is the correct wear pattern. Are these replaceable?

Offline edwardmorris

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Re: 1972 CB750 Four K2 -- Project "Ice Cream"-- ENGINE TEARDOWN
« Reply #217 on: January 05, 2014, 01:33:06 PM »
Where is everybody?  :(

Garage inaccessible again with all the snow. Since I'm stuck indoors, I decided to clean up the pistons. Did a preliminary clean, how do these look? There is definite pitting on all of them, worst are 1 and 4. Want be sure these can go back in before I do a compulsive clean :D all the oiling holes, ring grooves etc look great. The rings themselves look great, but I'm not even going to dare ask :D

Offline 70CB750

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Re: 1972 CB750 Four K2 -- Project "Ice Cream"-- ENGINE TEARDOWN
« Reply #218 on: January 05, 2014, 02:10:59 PM »
I would say pistons are fine and you could reuse rings if you put them back the way they were.  I was going to to that on the F, but one ring was broken - reringed it all.
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Offline edwardmorris

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Re: 1972 CB750 Four K2 -- Project "Ice Cream"-- ENGINE TEARDOWN
« Reply #219 on: January 05, 2014, 02:48:48 PM »
I would say pistons are fine and you could reuse rings if you put them back the way they were.  I was going to to that on the F, but one ring was broken - reringed it all.
This thread is why I wasn't gonna ask

http://forums.sohc4.net/index.php?topic=126776.0

I was just cleaning the damned things and one of the #3 rings just snapped! Ugh, I guess I'll be re-ringing as well.

Offline 70CB750

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Re: 1972 CB750 Four K2 -- Project "Ice Cream"-- ENGINE TEARDOWN
« Reply #220 on: January 05, 2014, 02:50:43 PM »
Everybody brakes a ring eventually :)
Prokop
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I love it when parts come together.

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CB750K3F - The Red
Sidecar


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Offline BPellerine

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Re: 1972 CB750 Four K2 -- Project "Ice Cream"-- ENGINE TEARDOWN
« Reply #221 on: January 05, 2014, 03:56:22 PM »
as for your main bearing shells they don't look too worn but you should measure or plastigage them same for the rod bearings .don't mix them up and try to see if you can see any color markings on them ie green yellow brown or black .IF they measure out ok some reuse them.also have you marked your rods 1,2,3,4 so they go back where they came from along with their shells?bill
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Offline RRRToolSolutions

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Re: 1972 CB750 Four K2 -- Project "Ice Cream"-- ENGINE TEARDOWN
« Reply #222 on: January 05, 2014, 04:00:11 PM »
Ed, while you're this far - I would suggest measuring the bores top and bottom for wear. Give us the bore measurements in line and 90 degrees to the piston pins (where most wear occurs). New rings is always a better way to go. If the wear is in tolerance, you could use a good Sunnen ball-hone and refinish the cylinders with a new cross-hatch so the new rings will seat. You'll have a happy engine too.

I'll go check, but I should have the snap gauges that you'll need for measuring and a ball hone in my shop for the new finish.

Regards, Gordon
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Offline RRRToolSolutions

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Re: 1972 CB750 Four K2 -- Project "Ice Cream"-- ENGINE TEARDOWN
« Reply #223 on: January 05, 2014, 05:57:25 PM »
Ed, I posted photos of your Rotor Puller Tool in the "For Sale" section. We made these from the best materials available and copied one I had in my tool cabinet so I know it works well. I'll get it to you this week.

Best Regards, Gordon



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Offline edwardmorris

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Re: 1972 CB750 Four K2 -- Project "Ice Cream"-- ENGINE TEARDOWN
« Reply #224 on: January 05, 2014, 08:06:40 PM »
Nice! Perfect timing Gordon, the crank and the rods are next on the removal, cleaning and inspection list and the rotor is still on, thanks!.

I can get the bore measurements if I can get those specialty tools. The pistons themselves I measured earlier for Terry with a caliper and they are the stock size (never bored). Honing was on my list anyway so I guess new rings will work out for the best.  The busted ones are coming in handy to clean the ring lands :D