Cb750k0 - any interest?

Well it’s a roller… but it still needs tires which are on order and should be here mid week.

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Polished up the rear fender. 60s chrome is a thing to marvel at. 52 years and still shining bright.

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I started to dig into my winkers and we’ll, they had certainly seen better days. My posts and bodies were ok but the internals were shot, been hacked up in the past and gonna be an uphill battle. Luckily Honda uses the same part on many models so a set of NOS ones were not too bad. Some battles aren’t worth fighting haha.
 
Yes Sir as John Cleese has it somewhere

" Stating the bleeding Obvious "

This is World Class work

I appreciate that! Although I probably can’t take too much credit. It’s all been done before, I didn’t come up with anything on my own haha.
 
New tires mounted. Gonna try some IRC gs-11s. Classic pattern, look good on the bike. We’ll see how long they last.

Got my harness ran, all my lights hooked up and tested (still waiting on front signals). It’s a very minimal system, nothing more than what is needed (excluding the parking light circut).

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Had some bulbs swapped in my gauges so I had to pull em back apart. Got em sorted.

Switch wires through the bars give it a real clean look.

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Got my motor up on the bench (what a beast!) and pulled my covers to do some initial investigation.

Looks like I’ll need to replace my primary chain tensioner as it’s crusty and braking down. This will require I split my cases.

I’ll swap out all my tensioners (primary and cam) and chains. Gonna run some cryogenic chains and see if the claim of no stretch and adjustment is true.

Will also need to replace my cam puck seals as they seem to have a slight leak.

Bike itself is physically almost to a stoping point as I can’t go much further without the motor back in the frame, so the motor will soon get some attention.

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You gonna freshen the top while you're in there?

Most likely.

If I had to guess, it’s never been opened so I’ll see what it looks like when I’m in there.

If it all measures within spec, a fresh hone and rings would be nice. And obviously clean up all the valves.

I wasn’t planning on pulling it apart but I’d be foolish not to now that I know the tensioners are hard and breaking down.

My primary chain is well within spec so if it hasn’t been apart before I’d guess it’s had a fairly easy life.

Still need to study up and go at it slow as I’ve never had one of these apart before so I’m pretty ignorant to the important details.
 
I have head that crank bearings are special and causing head scratching on CB750 .. But I may be wrong it is just a vague memory
From not a secure source.
I If remeber they are matched and tricky and expensive to redo. But again can be wrong.
 
I have head that crank bearings are special and causing head scratching on CB750 .. But I may be wrong it is just a vague memory
From not a secure source.
I If remeber they are matched and tricky and expensive to redo. But again can be wrong.

Crank bearings are a split bearing that comes in 4 different colors. Requires getting an alphabetic code off the crank and case, then using a chart to arange the letters and decipher the correct color. Easy peasy hahaha

Don’t think they go bad all that often though and havnt come across anything about head scratching yet.

The bearings are cheap, but seems a pain to do and obviously requires a tear down of the motor.
 
requires plastigauge not that bad to do. We hard chromed ground and rebearinged a 750 single cam crank back in the day.
PO had run a 12 extended fork, no rake, the extreme tilt back oil starved the motor, at least that was our theory. Cut the forks back to 6 over, raked the frame and ran the piss out that motor, all good.
Recently @JRP1 reminded me that he took that motor to his tech college engine class, and rebuilding it was the class project. :cool: We were verrrry tricky....
 
Got the top end all pulled apart, separated, labeled and sorted.

Here is what I’m working with.

I’m not quite sure what is excessive wear for these motors but if the rocker arms were in other motors I’ve been in, I would run em but one give me a little concern. The exhaust arm on cylinder 2. The others I think will polish up and the cam itself doesn’t show any real damage or excessive wear.
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I’m thinking I may get a new arm for number 2 and run the rest.
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There is a little score on the cam lobe of 2 but I think it will clean and polish up ok.

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Thoughts??

Barrels are clean, still show cross hatching.

Head got some carbon build up haha but it should soda blast off. Same with the pistons.

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Cam chain wheel is toast haha.

Clean the head and cylinders, fresh hone, rings, seals, gaskets, cam guide, roller, chain, replace rocker arms 2. - seems to be my plan, granted everything measures within spec.
 
A little bit of soda blasting to the head and it’ll clean up quite nice.

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Hopefully clean and blast the rest of the head tomorrow.

Getting the built up carbon off was quite a pain compared to others I’ve done.

I have the valves soaking in some solution over night to hopefully break it up a bit.

Exhaust ports probably wouldn’t hurt from a good sanding to smooth em out.
 
What brand/flavor soda are you using?
I like the results.
 
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