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Author Topic: 76 CB750K engine rebuild thread - With Video!  (Read 12412 times)

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Offline michrobi

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76 CB750K engine rebuild thread - With Video!
« on: July 04, 2009, 07:12:06 PM »
Today I am starting the rebuild of my 76 750K engine that is in my 78F.

Parts:

Gasket set (Cycle-X)
Oil Seal set (Cycle-X)
41 grind Webcam cam (Dynoman)
HD cylinder studs (Dynoman)
Adjustable cam sprocket (Dynoman)
Primary chains (mrcycles)
736 rings (Z1 Enterprises)
HD Tsubaki cam chain (Z1 Enterprises)
Cam roller and guide (Z1 Enterprises)
New OEM piston pins (epay)
Tube of Moly 60
Green plastigage
Engine Primer/Paint

Compression test  with an 8" hose yielded the following results:

(1) 91 lbs.
(2) 89 lbs.
(3) 62 lbs.
(4) 61 lbs.


I picked up my engine mount adapters at 11:30 today, and started at around 12. It's 7 pm now and I'm still sweating from just coming in the house...

It was my first time pulling the engine and I did it solo. I have to say I'm feeling pretty damn cool right about now.

Carbs, gas and oil tank off


Ignition cable


Negative power feed and alternator


Main drive sprocket. Look at the nastyness that was hiding under the chain cover. I would be shot in some states!



Was a whore about coming out...


Until I pulled off the aftermarket oil cooler mount (duh!). After that, I sat down and it jumped out and on to the jack by itself. And started wagging it's tail even.


Seven hours later...


Owe my back.   :'(
« Last Edit: July 18, 2009, 10:00:27 AM by michrobi »
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-Mike

'78 CB750F All stock except for the powerplant. Jived it off my Dad in the spring of '94. He had it since 1980 and it's the first bike I ever rode on.

Current project: http://forums.sohc4.net/index.php?topic=67756

How's them SOHC4 patches coming?

Offline Johnny5

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Re: 76 CB750K engine rebuild thread
« Reply #1 on: July 04, 2009, 10:02:10 PM »
That's one way to skin a feline. Nice job.

Good luck on the rebuild.
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Offline michrobi

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Re: 76 CB750K engine rebuild thread
« Reply #2 on: July 04, 2009, 11:52:46 PM »
And to finish off day 1...

Rocker cover off


Looks like this has been into, the screwdriver notches are on the inside for 1 & 2


Cam removed


Head removed


Head


Cylinders off and on the engine mount, ready for tomorrow.


Everything looks like it's in good shape so far. A good start.
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-Mike

'78 CB750F All stock except for the powerplant. Jived it off my Dad in the spring of '94. He had it since 1980 and it's the first bike I ever rode on.

Current project: http://forums.sohc4.net/index.php?topic=67756

How's them SOHC4 patches coming?

Offline ekpent

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Re: 76 CB750K engine rebuild thread
« Reply #3 on: July 05, 2009, 07:57:45 AM »
Allow me to compliment you on your shop. Looks very nice and organized with all the goodies to get the job done.!!!
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Offline michrobi

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Re: 76 CB750K engine rebuild thread
« Reply #4 on: July 05, 2009, 09:28:42 AM »
Thanks.     8)
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-Mike

'78 CB750F All stock except for the powerplant. Jived it off my Dad in the spring of '94. He had it since 1980 and it's the first bike I ever rode on.

Current project: http://forums.sohc4.net/index.php?topic=67756

How's them SOHC4 patches coming?

Offline michrobi

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Re: 76 CB750K engine rebuild thread
« Reply #5 on: July 05, 2009, 03:23:59 PM »

Pistons are a little scratched up, and the pins too. Those pins didn't want to come out. I'm worried the lines that match the pins on the inside of the rod wrist mean those rods are shot. Any thoughts on that?

Pistons


Looks like the last guy in here hammered a niche into the edge of the drum screw. I'm sure I'll be drilling that   >:(


Ever seen a balancer welded together like this?? every connection is welded in that way. Wow! That will have to be replaced I'm thinking.   ???


Not one spec of metal in the oil pan, and the screen is nice and clean on the pump. Heading back out to drill the shift linkage all out...
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-Mike

'78 CB750F All stock except for the powerplant. Jived it off my Dad in the spring of '94. He had it since 1980 and it's the first bike I ever rode on.

Current project: http://forums.sohc4.net/index.php?topic=67756

How's them SOHC4 patches coming?

Offline michrobi

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Re: 76 CB750K engine rebuild thread
« Reply #6 on: July 06, 2009, 06:01:52 PM »

The result of those notches...


Trying to keep it all together and in order, I hope I'm successful.


This has been the first time I had to drill every screw behind the shift cover. Sucked.


I've used 1/2" air on this and it refuses to pop free. Any idea what else I can try to get this rotor off? I'm stalled out on this part   ???

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-Mike

'78 CB750F All stock except for the powerplant. Jived it off my Dad in the spring of '94. He had it since 1980 and it's the first bike I ever rode on.

Current project: http://forums.sohc4.net/index.php?topic=67756

How's them SOHC4 patches coming?

Offline bwaller

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Re: 76 CB750K engine rebuild thread
« Reply #7 on: July 06, 2009, 06:10:15 PM »
Leave the rotor in place. Those welds are stock and unless you need to work on the starter clutch, it could stay put.
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Offline michrobi

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Re: 76 CB750K engine rebuild thread
« Reply #8 on: July 06, 2009, 08:51:09 PM »

Oh nice, as long as I can remove, clean, and replace the crank without having to take that thing off, I'll leave it.   :)
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-Mike

'78 CB750F All stock except for the powerplant. Jived it off my Dad in the spring of '94. He had it since 1980 and it's the first bike I ever rode on.

Current project: http://forums.sohc4.net/index.php?topic=67756

How's them SOHC4 patches coming?

Offline michrobi

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Re: 76 CB750K engine rebuild thread
« Reply #9 on: July 06, 2009, 10:49:10 PM »

Clutch as far as I can get. I'll need that special socket to get it off and I dont have it. I'll order one tomorrow.


Top case bolts removed and cases flipped. Can I leave the clutch in place, or does it have to be removed?


Closer look at the oil pump


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-Mike

'78 CB750F All stock except for the powerplant. Jived it off my Dad in the spring of '94. He had it since 1980 and it's the first bike I ever rode on.

Current project: http://forums.sohc4.net/index.php?topic=67756

How's them SOHC4 patches coming?

Offline mec

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Re: 76 CB750K engine rebuild thread
« Reply #10 on: July 07, 2009, 05:41:42 AM »
you can leave the clutch in place.

you can do a special socket by your own. this was a 22mm socket (second from right).

mec
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Offline michrobi

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Re: 76 CB750K engine rebuild thread
« Reply #11 on: July 07, 2009, 12:02:53 PM »

In that case I'll just leave the clutch in for now and split those cases. Is anything going to be hanging on to the bottom case when I lift it off that I need to watch out for?
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-Mike

'78 CB750F All stock except for the powerplant. Jived it off my Dad in the spring of '94. He had it since 1980 and it's the first bike I ever rode on.

Current project: http://forums.sohc4.net/index.php?topic=67756

How's them SOHC4 patches coming?

Offline michrobi

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Re: 76 CB750K engine rebuild thread
« Reply #12 on: July 07, 2009, 08:03:07 PM »
I want to take the cases to the car wash and zap them. Is it okay to do that, or solvent only?


Bottom case removed










Crank


A message from the PO


Transmission and bottom case


Top case


Time to clean the hell out of what is staying in the engine. I plan to solvent scrub every gear, sprocket and piece of removable whatever I find. Is there anything I shouldn't do?

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-Mike

'78 CB750F All stock except for the powerplant. Jived it off my Dad in the spring of '94. He had it since 1980 and it's the first bike I ever rode on.

Current project: http://forums.sohc4.net/index.php?topic=67756

How's them SOHC4 patches coming?

Offline Colonel

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Re: 76 CB750K engine rebuild thread
« Reply #13 on: July 07, 2009, 09:02:11 PM »
Your project has became my summer reading... Please continue with pictures; very good materials.
BTW, engine guts looks extremely clean to me  ;)
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Offline michrobi

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Re: 76 CB750K engine rebuild thread
« Reply #14 on: July 07, 2009, 10:17:10 PM »

Awesome, when I screw it all up you guys will know what not to do   ;)

Only problem with documenting it in such great detail is that the questions I have get lost in the blah blah and go unanswered. I think I need to post direct questions in their own threads and keep this to just tell the story. It helps keep me on task to know other guys are interested in my progress.
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-Mike

'78 CB750F All stock except for the powerplant. Jived it off my Dad in the spring of '94. He had it since 1980 and it's the first bike I ever rode on.

Current project: http://forums.sohc4.net/index.php?topic=67756

How's them SOHC4 patches coming?

Offline michrobi

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Re: 76 CB750K engine rebuild thread
« Reply #15 on: July 07, 2009, 10:39:57 PM »

Alternator






Top main bearings








Oil pump guides and O-rings. I can only get one of the three guides out


Lower main bearings




Kick shaft and sprocket/spring assembly






Gear forks removed




And finally for tonight, I'm stalled out on this neutral stopper at the bottom of this pic. After removing the bolt, I have no tool in my inventory that's thin enough to grab that stopper and turn it. It has only two flat spots and one side is only about 2.5mm from the case. It's  keeping me from getting something around it.
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-Mike

'78 CB750F All stock except for the powerplant. Jived it off my Dad in the spring of '94. He had it since 1980 and it's the first bike I ever rode on.

Current project: http://forums.sohc4.net/index.php?topic=67756

How's them SOHC4 patches coming?

Offline mec

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Re: 76 CB750K engine rebuild thread
« Reply #16 on: July 08, 2009, 01:09:26 AM »
the neutral stopper does have a M4 (?) thread. mount a screw and pull the screw together with the stopper.

mec
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Offline michrobi

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Re: 76 CB750K engine rebuild thread
« Reply #17 on: July 08, 2009, 01:38:04 AM »

I assumed it was threaded, but it just pulled away from the case. I've made some progress but I'm too tired to upload photos. I'll update tomorrow.
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-Mike

'78 CB750F All stock except for the powerplant. Jived it off my Dad in the spring of '94. He had it since 1980 and it's the first bike I ever rode on.

Current project: http://forums.sohc4.net/index.php?topic=67756

How's them SOHC4 patches coming?

Offline odin836

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Re: 76 CB750K engine rebuild thread
« Reply #18 on: July 08, 2009, 01:49:14 AM »
Currently about the same stage with my motor.
Keep the story coming, the detail is great!
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Offline michrobi

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Re: 76 CB750K engine rebuild thread
« Reply #19 on: July 08, 2009, 04:47:53 AM »

I can't sleep. I keep going over the transmission I just removed, trying to make it make sense in my head. I'm getting a little apprehensive.

So I got the neutral stop out, and the drum slipped right out of the case. But now that I think about it. If that drum was touching something, I don't recall it. Maybe the three forks?


Then the high gear comes out


Then the rest of the gears can be pulled out all together on the spindle




Then each gear can be removed, and there are three sets of clips staggered (sort of) on the spindle keeping the gears in place










This last part with the gears connected to the forks, connected to the drum (I think), connected to the main drive shaft in the upper case somehow   ???  has me wondering if I can get it back together. The top end from the crank up is pretty familiar to me, and I can do all of that much in my head for the most part. This trans has me a little frightened.   :-X
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-Mike

'78 CB750F All stock except for the powerplant. Jived it off my Dad in the spring of '94. He had it since 1980 and it's the first bike I ever rode on.

Current project: http://forums.sohc4.net/index.php?topic=67756

How's them SOHC4 patches coming?

Offline Toxic

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Re: 76 CB750K engine rebuild thread
« Reply #20 on: July 08, 2009, 05:29:06 AM »
Really enjoying your rebuild but what prompted the massive tear down of the bottom end?

Did you have some concerns?  It looks to be in great shape.

Or did you just want to clean and inspect?

Either way it's much appreciated.  Great tutorial.
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Offline michrobi

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Re: 76 CB750K engine rebuild thread
« Reply #21 on: July 08, 2009, 06:40:34 AM »
The cases have to be washed and painted. They're caked and baked with oil and sludge. I just got back from the car wash with them and the power washer didn't touch the stuff. The bottom case is going to need a couple days in the solvent bath at least, and more likely a week. I'll see what I can get a machine shop to blast them for.
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-Mike

'78 CB750F All stock except for the powerplant. Jived it off my Dad in the spring of '94. He had it since 1980 and it's the first bike I ever rode on.

Current project: http://forums.sohc4.net/index.php?topic=67756

How's them SOHC4 patches coming?

Offline michrobi

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Re: 76 CB750K engine rebuild thread
« Reply #22 on: July 08, 2009, 04:44:27 PM »

Dropped the cases off this morning and picked them up just now. Clean as a whistle and they did it while I slept. Best 25 bones I ever spent   ;D
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-Mike

'78 CB750F All stock except for the powerplant. Jived it off my Dad in the spring of '94. He had it since 1980 and it's the first bike I ever rode on.

Current project: http://forums.sohc4.net/index.php?topic=67756

How's them SOHC4 patches coming?

Offline Colonel

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Re: 76 CB750K engine rebuild thread
« Reply #23 on: July 08, 2009, 05:57:43 PM »
Can't wait to see the "after"... I take your word for the "caked and baked with oil and sludge" as it looked quite clean from your previous posts...
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Offline michrobi

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Re: 76 CB750K engine rebuild thread
« Reply #24 on: July 08, 2009, 06:05:20 PM »

Here's a before...   :o

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-Mike

'78 CB750F All stock except for the powerplant. Jived it off my Dad in the spring of '94. He had it since 1980 and it's the first bike I ever rode on.

Current project: http://forums.sohc4.net/index.php?topic=67756

How's them SOHC4 patches coming?
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