Topic: 1978 cb750k- and so it begins

[Dime]

Bought this as a supposed runner but not so much.

Drained the tank and carbs. Topped up with fresh gas. Have gas at the carbs, have confirmed spark.

Reset each mixture screw to 1.5 turns.

Wants to.run and caught for a second but won't run.

Pulling plugs next and replacing.

Lots of work ahead of me. Many plans for this scoot. Should be fun.

[Dime]

She is all there but lots of work to do. Side covers are a write off though

[Dime]

All right it lives! Running a bit rough but it did fire right up after I changed the plugs. Takes the throttle good just some poping from the pipes.

Now I will start checking valve clearances and adjust the cam chain tensioner.

[HondaMan]

Wow! I did a 100% resto on one that looked like yours when I got it.
When I listed it afterward, it lasted 15 minutes. When that guy rode it home to the garage he had (rented from his landlord) the landlord bought it from him on sight at a healthy profit. It turned out that the landlord had the exact same 750K8 when he was in college and regretted selling it ever since. You ought to see it now: it looks like 5 layers of wax have been applied!

Then the guy who bought it form me came back and bought my then-in-resto 750F1 when it was half done: about 5 months later he rode it away from here. He had it for 15 months before someone talked him out of it (it's in Fort Collins, CO now) and the original guy came by with a CB550K1 in need of help.

So...it's the star of my next book. This weekend I'll get the rear wheel assembly back together and install new front wheel bearings, and maybe get close to starting up the newly-rebuilt (and all heavily photo-documented) engine.

Next, it needs paint...gold...flake...

[Dime]

Wow! I did a 100% resto on one that looked like yours when I got it.
When I listed it afterward, it lasted 15 minutes. When that guy rode it home to the garage he had (rented from his landlord) the landlord bought it from him on sight at a healthy profit. It turned out that the landlord had the exact same 750K8 when he was in college and regretted selling it ever since. You ought to see it now: it looks like 5 layers of wax have been applied!

Then the guy who bought it form me came back and bought my then-in-resto 750F1 when it was half done: about 5 months later he rode it away from here. He had it for 15 months before someone talked him out of it (it's in Fort Collins, CO now) and the original guy came by with a CB550K1 in need of help.

So...it's the star of my next book. This weekend I'll get the rear wheel assembly back together and install new front wheel bearings, and maybe get close to starting up the newly-rebuilt (and all heavily photo-documented) engine.

Next, it needs paint...gold...flake...

That is awesome man. I am not planning on doing a resto on this one, that being said I plan on keeping all the original parts so if God forbid the day comes I have to sell it the parts will be there.

I have an early style rear fender to go on it, current stock one is in rough shape. Want to do a cafe style seat but am having trouble finding one that wouldn't involve removing the factory latches. Have a spare front fender I am going to bob, it is in rough shape but will be good when I am done with it. Both fenders are going powder coated gloss black.

Have to do the cam chain tensioner today. Did the valve clearances last night and it is running much better.

It puked gas on the floor while on reserve after running so have to figure that out.

Still planning on getting the steel dragon air box but for now the factory air box will do. Just have to figure out how to change the air filter once it gets here.

[Dime]

Did the cam chain tensioner adjustment and the engine is much quieter. Only problem is it is not running on cylinder 1. Confirmed I have spark. Just picked up another compression tester because I loaned mine out never to be seen again. Will test compression next on all four cylinders.

It is puking gas so I am inclined to believe that number 1 carb is acting up. Number one plug is fuel wet too.

All part of the process.

[Dime]

Not the numbers I was hoping for on the compression test

1- 72 lbs
2- 71 lbs
3- 65 lbs
4-100 lbs.

Looks like I am into a rebuild right off the hop. Bummer.

[Dime]

Retested the cylinders with an open throttle and it came up to 120's across the board. I am not satisfied with those numbers.

Started stripping the bike today and will pull the engine to do the top end.

The rest of the bike is getting stripped to the frame and I will be doing a complete rebuild on this bike.

It won't be a restoration because that is not my style. But it will be a nut and bolt rebuild.

I know this will take longer and cost more in the long run but I will have the bike I want when it is done. I can live with that.

[Dime]

I am really glad I decided to do a full teardown on this bike.

The wiring is absolutely shot. Between melted wires and ridiculous twisted joins, no connectors, it is enough to justify a full go through.

The frame is rusty too. So it will be good to get it clean and either fresh paint or powder coat.

Progress is progress.

[Dime]

Took a break from tear down and decided to work on the air box.

I am keeping the factory air box for a number of reasons. One the cost of a modern bread box. Another being the issues with cross draft and rain with the bread box.

After reading a post on here I removed 4mm from the inside of the air box inlets.

This is supposed to elevate the turbulence at higher rpm.

Other than having to replace the boots on the air box it is in good shape.

[kerryb]

Wow! I did a 100% resto on one that looked like yours when I got it.
When I listed it afterward, it lasted 15 minutes. When that guy rode it home to the garage he had (rented from his landlord) the landlord bought it from him on sight at a healthy profit. It turned out that the landlord had the exact same 750K8 when he was in college and regretted selling it ever since. You ought to see it now: it looks like 5 layers of wax have been applied!

Then the guy who bought it form me came back and bought my then-in-resto 750F1 when it was half done: about 5 months later he rode it away from here. He had it for 15 months before someone talked him out of it (it's in Fort Collins, CO now) and the original guy came by with a CB550K1 in need of help.

So...it's the star of my next book. This weekend I'll get the rear wheel assembly back together and install new front wheel bearings, and maybe get close to starting up the newly-rebuilt (and all heavily photo-documented) engine.

Next, it needs paint...gold...flake...

Oh goody, I have a couple 550 projects in the wings.

[BenelliSEI]

Looks like a solid beginning. That compression number shouldn’t mean instant tear down. Rebuild the carbs and get it running smoothly. Put some miles on it. Change the oil a few times and you might be surprised how well it runs.

[Dime]

Looks like a solid beginning. That compression number shouldn’t mean instant tear down. Rebuild the carbs and get it running smoothly. Put some miles on it. Change the oil a few times and you might be surprised how well it runs.

I appreciate the advise but one thing I forgot to mention is it has a good oil leak. So I am going to do the top end and know exactly what I have when it is done.

Been reading the leak free top end thread and he uses HD studs so I will most likely go that route.

The engine will be one of the last things getting done as I have decided to do a full on frame up rebuild.

The only thing not salvageable right now are the side covers and the rear fender. I planned on bobbing the fenders anyway but have the original front fender that came off but is in rough shape, but fixable. The original rear fender will serve my purposes once I do some fab work. That leaves me with a good front fender and I will buy a rear fender to have on hand to put it back to stock if need be.

[Dime]

Well a pleasant surprise so far is that somewhere along the way the 78 was converted to 530 chain and sprockets.

All the screws on the engine cover for the sprocket are stripped so I have yet to see the condition of the front sprocket but the rear is in great shape. The chain will need either a good clean up or replacement however.

One less thing on my to do list though as I had allowed for the 530 chain conversion.

[Dime]

The front sprocket is not the right one for the 78. Need the one with the raised face.

On another note the engine is out. Used a 6ft piece of pipe ratchet straps around the pipe and engine. Pipe supported by crates and scissor Jack's. Jack's allowed me to raise and lower engine as needed and I just wiggled the frame out from the engine while it was on it's center stand.

[Dime]

Love Lucas taillights. This is going to look great on the bobbed rear fender. This is not LED. I will not be running LED on this bike if I can help it. This is also a metal housing not plastic. Real quality piece.

[calj737]

All the screws on the engine cover for the sprocket are stripped so I have yet to see the condition of the front sprocket but the rear is in great shape.

It’s been my experience that if you drill off the head, remove the cover, the shanks of the screws will turn out very easily. There seems to be a propensity for the underside of the head to corrode against the cover and then unaware owners use Phillips screwdrivers to install/remove the screws and strip them.

[Kelly E]

All the screws on the engine cover for the sprocket are stripped so I have yet to see the condition of the front sprocket but the rear is in great shape.

It’s been my experience that if you drill off the head, remove the cover, the shanks of the screws will turn out very easily. There seems to be a propensity for the underside of the head to corrode against the cover and then unaware owners use Phillips screwdrivers to install/remove the screws and strip them.

If you use left hand drill bits the cover screws usually unscrew just before the head pops off. The heat from drilling breaks the the corrosion.

[Dime]

All the screws on the engine cover for the sprocket are stripped so I have yet to see the condition of the front sprocket but the rear is in great shape.

It’s been my experience that if you drill off the head, remove the cover, the shanks of the screws will turn out very easily. There seems to be a propensity for the underside of the head to corrode against the cover and then unaware owners use Phillips screwdrivers to install/remove the screws and strip them.

I actually used an easy trick I learned when I was an engine builder.

If a Philips is stuck or stripped get a Robinson bit on a 3/8 socket drive with an extension. The Robinson must be just slightly bigger than the center of the stripped Philips. Place in center of stripped head, tap the extension 3-4 times with a hammer and back out with 3/8 drive ratchet.

Works most every time.

[Dime]

Now it is a matter of time, money and learning how to restore one of these 750's.

[kerryb]

You do have Mark’s book, right?

[Dime]

You do have Mark’s book, right?

Not yet but will be buying it. Trying to gather some money for tools first

[Dime]

Making some progress.

The rear wheel axle on the kz1000 ltd is 20mm. The same as the cb750. The kz axle is shorter so I will have to use the cb axle with the kz wheel and have spacers made. Not sure about alignment yet with the front sprocket but when lineing up the two wheel on their sprocket side the sprocket carriers look pretty close. Rough way of doing it but I figure it is close enough that if I need a spacer for the sprocket it is easily done.

[Dime]

The rear fender was gone beyond what would be any good to someone in stock form so I decided to go ahead and modify it.

Cut the tail piece off just before the holes for the taillight.  Cut the entire section with the holes for the taillight out. Will have my buddy weld the tail section onto the cut fender. This will allow the fender to look stock but shortened.

I then have to figure out mounting the lucas taillight. After that it will be ready for powder coat.

[Dime]

Well this is just working out quite lovely so far.

I received the triple tree for the kz1000 ltd today. The stem in the kz1000 ltd triple tree needs to be pressed up in the bottom clamp by 1.6 mm and it will match the length of the cb750 stem.

The use of all balls conversion bearings part numbers 99-3520-5 and 99-3521-5 allows me to use the kz1000 ltd triple tree complete once the stem is adjusted the 1.6mm upwards.

Now that being said I will not be using the top clamp. I will be sending it off to a fabricator I follow in Nova Scotia so he can machine a new top clamp out of aluminum.

Pretty pumped.