Topic: 1978 CB750K - Stock Rebuild

[ZanVooden]

So I figured its about time I start a build thread

I received this 750 K8 last year in the spring for FREE. The PO (a buddy of mine) didnt want to spend money on it to get it fixed, and I offered to take it off his hands. When I got it the engine turned over, but would not start or even fire once. About 50,000 miles.  Plenty of dents and rust. Not bad at all for free. Plan to restore the bike to stock, or near stock.








Got the bike home (Peoria, IL) from Milwaukee (where I go to school) and started the tear down to find out why it didn't run. Compression check resulted in pressures all over the place.







Everybody loves carbs.... Right?....



After inspecting everything found out that the valve guides were badly worn, valve springs were weak, piston rings were shot, and as you can expect everything dirty and full of crud.
So starts the clean up and polishing. Lots and lots of polishing.









So starts a the reassembly.








And that's about where it sits now. This past weekend I installed tapered bearings, and cleaned up the headlight, ears, turn signals, and front emblem. I dont plan to put the fairing back on, just not a fan of the look with the fairing. Also pulled the forks apart, cleaned, and installed new fork seals and dust boots. Disassembled the front caliper to rebuild it.

Currently waiting on a caliper seal, brake pads, and master cylinder rebuild kit.
Plan to re-paint the tank. have side covers, but need painting as well. Seat will be recovered with an orginal looking seat cover, and adding the seat trim as well.
Will post pictures as progress is made.


Yesterday picked up another 750 K8 running with a few electrical problems (headlight and turn signals) and some clean up needed for $700. I'll post picture after this weekend.

[andy750]

Hey looks good and I am eager to hear how it runs when finished. I like the look with the pipes.

good luck
Andy

[SanDogDewey]

Looking good! Did you just do the rings and valve guides and springs?

I got my '77 with the fairing and King/Queen seat. The fairing was the first thing to come off! Heading down to the upholstery shop today to see how the seat is coming.

[HedNut]

Hey! This is great... looks good too.  I have the same bike, mine cost me a few bills though...and it doesn't run.  How did your engine turn out??  I'm looking forward to seeing the finished dealio running amuck on the streets!
Cheers! And keep up the good work!

[jackofclubs]

great job, I did the same job last year on a 750 hondamatic. Very satisfying.

[ZanVooden]

Looking good! Did you just do the rings and valve guides and springs?

I got my '77 with the fairing and King/Queen seat. The fairing was the first thing to come off! Heading down to the upholstery shop today to see how the seat is coming.

I did pretty much everything on the top end. Didnt split of the case. took a chance that the rod and crankshaft bearings were ok. New rings, new gaskets and seal, new springs, new guides. Reused the valves but had them and the seat ground.

Hey! This is great... looks good too.  I have the same bike, mine cost me a few bills though...and it doesn't run.  How did your engine turn out??  I'm looking forward to seeing the finished dealio running amuck on the streets!
Cheers! And keep up the good work!

Engine turned out great. Still running a little rough, just trying to break it in. Hoping it will smooth out after some time, and hopefully some road time soon. But it look awesome after all the polishing. I also coated all the polish aluminum with high temp clear engine enamel.

I'm thinking I might have an issue with the accelerator pump on the carbs because when I twist the throttle the engine "bogs" down a bit and almost dies. But if I easy the throttle on it'll rev up just fine.

Once I get the front wheel back on I'll try to take a video of it running for all to enjoy. It does sound pretty awesome.

[Jerry Rxman Griffin aka MuthaF'er]

Hooked already, huh?! Sounds like a good project for a mechanical engineering student.

[ZanVooden]

Well its finished.

[cb750k7]

VERY NICE JOB!!!!!!!!!!!

What did you use to polish the engine and chrome?

Cheers,
Jona

[andy750]

Very nice work and I bet that exhaust sounds great...I used to have one myself ;-)

Well done
Andy

[Sheik Yerbouti]

Where did you manage to find rings for the '78? I'm searching for em right now.

Good looking bike.

[ZanVooden]

VERY NICE JOB!!!!!!!!!!!

What did you use to polish the engine and chrome?

Cheers,
Jona

Used just a cheap Aluminum polishing kit from an Ace hardware. It came with different heads which could be mounted in a drill. then used with 3 grits of polish.

Where did you manage to find rings for the '78? I'm searching for em right now.

Good looking bike.

I believe the rings came from BikeBandit.com. I'll look it up, and let you know if thats different.

Very nice work and I bet that exhaust sounds great...I used to have one myself ;-)

Well done
Andy

Love the exhaust. Look beautiful and sounds great. Like it so much, found some on ebay awhile back to put on the next bike.

[ZanVooden]

So finally got the bike on the road this past Sunday. Granted it was only up and down the neighborhood street. Got the bike warmed up and it ran absolutely wonderful. Revs are hanging a little so that will have to be addressed. also after the ride did a check over the whole bike for leaks and found that the valve cover is seeping oil, So hopefully all I have to do is tighten down the valve cover screws.

Thanks for all the complements.