CB750 K0/K1 Hybrid

[robin1731]

Doing it without the plugs is much easier.

When you do get the engine in and wired up do this. After you have the oil in. Remove the plugs and use the electric start to turn the engine over. Crank it until the oil pressure light goes out. Then put the plugs back in. If you static timed it right and the carbs have fuel it should start up pretty easily.

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[Lucien Harpress]

Hey, guess what! Update!

I got tired of looking at a bike that needed way too much work as-is, so I got lucky and found ANOTHER frame, this time in one piece AND with a title. Because of this, I can finally do something I haven't done in a while- put pieces BACK TOGETHER!

First thing's first- the easiest way to get a CB750 motor back into the frame (can attest that it works, and lots better than when I removed it).

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...and this is where we currently sit. Engine, battery box, oil tank, main wiring harness, rear fender. I've been cleaning up and painting some of the really bad parts, so while you can still tell it's been rusted at some point, it looks a LOT better than it did before.

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The crusty engine covers are going to be pulled and polished later on, assuming I can get the bike running. I can do that with the engine in the frame no problem, so I can put that off.

I'm adding a bit every day. I'd like to get the back end on next, then deal with all the wiring/triple tree/fork mess up front last. THEN, once we get a roller, I can start picking at running/quality of life issues. Definitely happy to be making some progress, finally.

[Easter]

More progress than mine (Long term CB750) at my speed it will be long indeed. Took the engine to some mechanic friends of mine to try to get the exhaust stud out that made it so hard to remove from the frame. Triple nuts and torch, etc. still wouldn't budge it. Mechanic noted that it looked like it had run very hot at some point and gaulled the stud. So I am not sure where to go from here. It would be an expensive project at best plus no title and maybe not a useable engine.

Yours looks much more manageable. Always liked that stock color. Mine (in the 70's) had the green tank but same pattern trim.

[Lucien Harpress]

My biggest worry right now is the wiring harness. Wiring is not fun for me at the best of times, and I can't afford a new one any time soon, IF I can find the right one for the year. The only upside is that it doesn't seem to be cut up at all, so if I DO have issues, I can at least follow the diagram straight-up.

I'm also playing the, "can I clean this or should I replace it" game with EVERYTHING.....

[Lucien Harpress]

Guess what? My baby's got both her shoes.

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This is also the first time that front fender has been on this bike, and looks REALLY nice.

Sure, the tank needs de-rusted, painted, and MAY be full of pinholes, the front forks need rebuilt and require new downtubes (probably), and that's just the parts on the bike.... but DANG, doesn't it look good?

[Easter]

Looking good. I always preferred the early style fender with double hoops. I think the year after yours Honda shortened the fender and only used the back hoop.

[Lucien Harpress]

The double hoop held on for a bit, '75ish maybe? What they DID change was the blasted center bracket/fork brace, into a symmetrical unit, unlike the asymmetrical one from 69-72. I ended up having to find a later fender in decent shape, then drill out the rivets and bolt up my original bracket.

In any case, MORE PHOTOS:

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Now, assuming I try using the original coils for now, I'm nearly to the point where I can potentially try to fire this baby up. At bare minimum I need a new ignition switch and probably points, but the biggest thing is figuring out what to wire up to turn the motor over. Much as it looks like a motorcycle, I don't what to go a whole lot farther until I know I can at least get this baby to fire.

[Easter]

Looking really good for unrestored.

[JSBail]

At bare minimum I need a new ignition switch and probably points, but the biggest thing is figuring out what to wire up to turn the motor over.

If you do get another set of points then do your best to get a set of genuine TEC points, the cheaper Daiichi points and condensers that are easily available tend to be nothing but trouble. It's not uncommon for 750 owners to toss the new Daiichi points and throw their original 40 year old TEC points and condensers back in.

[Lucien Harpress]

It's definitely a bit of a poor man's restoration. I splurged on a couple of big-ticket items to get pretty clean versions (front fender, exhaust), took the best parts between two bikes, and am hitting some of the black parts (frame pieces, foot pegs, gauge housings, etc.) with some Case tractor paint out of a spray can. Not how I'd prefer to do it, but for right now it's what I can afford, and will be good enough for a daily rider (hopefully).

I've seen a concours restoration SOHC CB750 at nearly every show I've been to. This will never be that. If I can get it "clean" and running, I'll be happy.

[Lucien Harpress]

Because I was tired of it sitting in the basement, I figured I'd get half my exhaust on.

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I would've had the whole set on, but one of the flanges is completely frozen into the old pipe. Heat, pry bars, nothing. A replacement is in the mail.

I still need to find out how to static test a coil to see if it's still good. Anyone know the ohm measurements for a set of FL-703s.....?

[JSBail]

5 ohms. Scroll down to reply #4 for more details http://forums.sohc4.net/index.php/topic,5752.0.html

[Lucien Harpress]

So, I ran some tests on my coils, and I got some good news and bad news. The good? All the resistance measurements seem to be good, or really close to. Good enough for me to use them for now. Bad news? They ARE 40 year old coils, and the wires are pretty shot. They're solid, but don't flex that well. In addition, I clipped off the bad ends and re-installed the plug caps, but they still only screwed in so-so. Hopefully they work well enough to prove this bike is worth throwing more money at.

I also fixed a crack in my headlight bucket, and tomorrow will be sent connecting all my wires up, save for perhaps the tail end (it needs new connectors). I'm also probably going to need a new battery- my current one doesn't hold a charge. It's also sat for a year or two, so there's that. I'm going to attempt to refill some of the cells first, because again, it's only got to hold a charge long enough to get some testing in.

I also managed to get my exhaust flange installed, BUT ruined one of my exhaust clamps in the process. I've got a few new ones coming, but again, it's one more thing to wait on.

Still, I'm a lot closer to a startup than I was anticipating. I may be allowing myself to get a bit excited.

[Easter]

"Endeavor to persevere"

[JSBail]

So far I've yet to see a set of coils from an older inline 4 Honda that didn't have stiff plug wires, kind of makes me wonder if they ever were all that flexible even when new. NGK does offer a splice where you can snip the old plug wire near the coil and run new plug wire from that point on and I've seen some where they dig into the coil to completely remove the old wire and install a new one but they had to do some hacking to do it being that wire is molded into the coil. I've ran a previous cb550 and my current cb750 with their original coils and stiff plug wires with no problems so yours ought to be good enough to fire the bike up so long as all the spark plug resistor caps are good.