Author Topic: 1974 cb750 Cafe. Disassembled, about to start rebuild! Like it?  (Read 1109 times)

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Offline ScarlettRocks

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    • Scarlett. She's a motorcycle, and a rock n roll band.
Hey everyone, I'm Tom, excited to finally contribute something cool to the forum. Me and my old man are avid readers of the forum, you guys have helped us COUNTLESS times. Always find the solution here. Anyways, we've got a 1974 CB750 K4, in an awesome cafe style, and paint job. BUT, she's in a gazillion pieces. We're about to start the engine assembly, it's already fully disassembled and stripped of the paint it came with. I'll start from here on the next post for those who want to jump right into engine rebuild discussion. Otherwise I'll start from where I should have started posting back in August. FROM THE TOP.

Here's the girl.


Picked her up on Craigslist in August of 2012, from Savannah GA, dressed as she is on the bed of the truck. You know I spent the weekend down there too... $600 for the bike. Steal huh? A couple of catches, to be noted. Seized engine, wiring all out of whack, no fluids in the bike, and "hadn't run in 15 years". All of that behind a pretty face, I'd say. So I nabbed her, made it home after celebrating in Savannah, and rolled her down to my old man's basement shop. Coolest cafe shop in Georgia, we like to say.  ;D

We began by tackling the seized engine. After all, you're not gonna go to fast on a dead engine... Acentone and ATF, was the cocktail special of the evening, and she drank about a gallons worth of it. Took out the spark plugs, and funneled the liquid into the engine, shook her side to side a few times, put some cardboard underneath, and turned out the lights. Thanks to the forum for the cocktail recipe!

A month later, after being a good dog and not fiddling with it, just going downstairs to stare at it, I grabbed the breaker bar, and popped it onto the crank. Wiggle, wiggle, wiggle, back, forth, FREEDOM. She let loose, the evil binds she had upon her, and the motor spun freely. No apparent friction at previous point of sticking. Good news! High fives all around, and on to the next step. Since I didn't know where the hell this bike has been in the past 40 years, especially wearing that dress, we decided to fully disassemble and assess engine condition, along with tend to the wiring issues. We're about here at this point.

I told my dad I was excited to get the engine out of that bike, and he told me not to be a dumbass and try to do it alone. Well... You can probably tell how the rest goes. I laid down lots of cardboard, pulled up my pants, and laid her over as easily as possible. After a long 15 min of wiggling the friggin frame, finally separated it from the engine. If I wasn't an idiot, I would have removed the wheels, and just lifted frame, but that's just what my back had to say the next day. That puts us here!

She spit out one last blob of oil. Mom wasn't happy.

Once I got it on the cart, I began disassembling everything. Any bolt I could find, until my old man got home and about broke the breaker bar over my head... Made the overexcited error of not really labeling while disassembling, just separating in tupperware. Oops! We decided from this point, my worst error of all, to tend to the valves, and just change the gaskets throughout the engine. My ERROR was not doing a rebuild at that moment, but I didn't think/hope it would be necessary. Naive, indeed. Learned the hard way now, in April 2013, rebuilding the engine finally. Anyways, we adjusted the valves, and just changed the gaskets on the exterior case, valve cover, clutch, points, etc. Just gaskets. Foolish. But we also wanted to really just see if the damn thing would turn on or not.

So once the engine was patched up, we got to wiring issues. The wiring harness was old as sin, including the left side components (rectifier, regulator, etc). Also, both left and right hand switches had been rewired, from the interior, meaning re-soldered to the connectors. Cool, right? Not really, the dude didn't coordinate color in any way, according to the schematic, so it wasn't pretty figuring out the duty of each cable, labeling it, and comparing it to the function and color on the schematic, and chart it that way. It worked, after a long ass time. Starter/button didn't ever wanna work, so we stuck a wrench between the posts of the started solenoid, and that starter threw a party. Ok cool! Not so much. Old man's troubleshooting led us to cracking it open and figuring out WHY it wouldn't work, because the power was there. Turns out, the little metal bar that runs across the inside of the starter solenoid to make contact with the posts, had bent downward, to where it simply wasn't making contact with the posts when activated. Urg. Bought a new one. We installed it, tried it like twice, it worked, and it stopped working. FRIED. Mannnnnnnnnnn, so we decided from there it'd be a kick start.  8)

Also bought the voltage regulator, and a NEW wiring harness, which was one of the best decisions we made. Bike came with a new key ignition. Also bought coils, sparks, and noticed that the points had previously been replaced, so decided to leave them for now. Installed all of this, after many weeks of work. Rewiring this thing is not fun, but I'm much more confident I could do it better and more efficiently at this point.

Now we started looking around the rest of the bike for what needed to be handled. Don't have many pics of this stuff, so I'll list what else we did.

Rebuilt master cylinder, caliper, piston seals, and speed-bleeder (AWESOME product by the way, makes the bleed job effortless)

New airfilter, and airbox boots, but I never did end up using that airbox. Anybody wanna buy it? :) (seriously though, message me)

Bike came with pods, which I hear are the enemy, but I read a LOT otherwise too. Lots of into on here about them. Links?

Rebuilt carburetors by the old man himself. Bought 4 rebuild kits, and got to it. He actually soaked them in pine-sol for like 2 days, and they came out shinier then when they were new...

Sprockets, brake lines, throttle and clutch cables, fuel lines, and chain.

^^I'll have some questions about those damn throttle cables in about 3 weeks.

Seized engine - CHECK
Wiring - CHECK
Rest of bike - CHECK
When was the last time this thing ran again? Psh.

Wanted to post a video of how ferocious this thing sounds, but I can't. :(

So it ran, which was AWESOME. Idled alright, not correctly though. But it leaked oil out of the oil filer, like, a LOT. And from the top RPM counter cable. Back inside, tweak tweak tweak, and back out the next day. VROOM. We decided to ride her up to the front yard and try it out, for the first time.

Would upload a video, but not allowed I don't think... boss?
Pics will do. Wrapped pipes too, forgot to include.











Gnarly little checkerboard pattern. I'd say it's a bit much, personally, but it suits her mean self just fine also.

This is where this story gets sour. SECOND GEAR. It slips out, or barely clicks into it. Lots of clutch cable adjustment, lots of hope, but it won't stay in. Damn. I rode it around a few times, rode across town, and came back, down to the basement once more. What I think happened to second gear, is that the dude who had it behind me tried countless times to unjam the engine by riding downhill in second gear, clutch in, and popping out the clutch. Enough times may have damaged the fork, or drum in a way. Was kind of difficult to diagnose transmission without cracking the case. Keep reading!

That puts us right about where we are today. We decided at that point, that our next homework was to rebuild this engine, the CORRECT way. Transmission, obviously, full gasket set, piston rings, cam chain tensioner set, oil cooler mod, electronic ignition, and a good paint job.

Before that, we wanted to get the engine cleaned up, on the EXTERIOR too. Paint looked like friggin truck bed liner, disastrous. And, scratches exposed that it was painted red underneath. Sheesh. $50 worth of paint stripping supplies, including gloves, stripper ( ;)) and a beer pong table on the back deck, and we had our own paint stripping business going. We painted lots of product onto the case parts, let them sit for 30-45, then hit them with a pressure washer, and another round of paint stripper, and a final wash. This is about where I'm at now fellas, I've got me a shiny engine :)







The bike also came with that tail piece made, with lights and license plate mount included. We had to tend to the wiring, of course, but worked! Forgot to include.

So, I've ordered my necessary parts, and am waiting to hear back from Ken at CycleX about my options with transmission. Already sent it his way, hoping to hear back by tuesday or wednesday.

Picked up a full gasket set and oil seal set, and piston rings from CycleX. Going to get my oil cooler from them too, and eventually a good exhaust. Making awesome products, by the looks of it! Actually wanted to get the higher grade gaskets they sell that claim to not have to be re-torqued after rebuild, but accounting wasn't happy about it, went with the regular full gasket set and oil seal combo for like $90, good deal!

Pamco and oil cooler will come eventually. Figured i'd get what needs to be done to get it running. Transmissions kinda vary in price on the cyclex website, so I'm not sure what it'll run, but I'm excited to get it back!


Here's some other cool pictures I've got, regarding the bike rebuild.

Here's the basement shop, not too shabby eh? Expecting to get a lift in here soon...

The Artillery


Thoughts on a king/queen seat, with the passenger seat shaved off, and kinda rounded down? Put the stock fender under it, painted black. I dig it? Or, use the tailpiece I have...



My dad's bike, 1981 CB750custom with 1100 ORIGINAL MILES ON IT. Still has FACTORY tires on it. Incredible find of his. Runs great, has vaccuum leak/sticky throttle issue to be solved. Ain't she pretty? I want him to cafe it out, and rip around the city with me... :)




Well, I'll continue this as I go, but waiting on parts now, and excited to be on the streets soon. (I hope).

Hope you've enjoyed the write up of this crazy rebuild I've had to do. Spill comments, questions, jokes, and pictures of pretty women or bikes. Thanks guys!

Offline AgPete139

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Re: 1974 cb750 Cafe. Disassembled, about to start rebuild! Like it?
« Reply #1 on: April 29, 2013, 08:22:47 am »
Nice find. It's definitely a cool bike.

I actually found your bike through a Google search for "CB750 cafe red frame."

I'm doing a full rebuild myself, and there's a lot to address on the bike. I'm currently trying to think of a paint scheme and design for the powdercoat & paint.

Keep us up to date on changes, man. Good luck!
K5 -- Cafe Racer in progress

Offline davidtime

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Re: 1974 cb750 Cafe. Disassembled, about to start rebuild! Like it?
« Reply #2 on: April 29, 2013, 08:40:50 am »
Definitely a killer score for 600. I like the paint. Personally I prefer that ducktail over a king and queen seat.