My 1981 Honda CB750K Project Bike

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My 1981 Honda CB750K Project Bike

Hellbilly429
Hey guys, I finally got some pics of my bike and after returning to this forum a million times for advice throughout my build I finally decided to become a member. I picked up my 81 CB750K at the perfect time for what seemed like a perfect price. This is my first bike, and I got it for $400. Don't have original pics but have what I got so far after all my work. I really want to make it look just badass and evil, but idk if my budget will allow me to do that, but I have started with the mirors and handlebar grips.








I think I have about $300 or $400 into parts so far and am now just waiting on my new regulator/rectifier and alternator brushes to come in, then just need to get it timed properly and set the idle correctly and i should be able to ride finally, just in time for the season here in NY!
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Re: My 1981 Honda CB750K Project Bike

TOOLS1
Administrator
Welcome to the forum. Nice bike. In my opinion the coolest, most bad ass bikes are always done on a short budget. "Use your hands, not your wallet."
TOOLS
Life is not about the number of breaths, you take, but the moments that take your breath away.
I don't have an anger problem. I have an idiot problem. Hank Hill
Never confuse education for intelligence.
Happiness is a belt fed weapon.
I just can't imagine what could go wrong.
No fire? No explosions? So whats the point of your story?
Those who are too smart to engage in politics are punished by being governed by those who are dumber. ~Plato
It couldn't be done, but the darn fool didn't know it, and did it anyway.
We all got problems. Ksharp
I like vintage bikes because they take me away from the clutter of technology that I work with everyday and back to a simpler time of mechanical elegance and simplicity.. "ninadm"
Darkwing Duck: The worst part of public transportation is the Public.
"That is awesome shit there" Re-Run
"Fear nothing, attack everything" Eric Berry
" Oh, you read that on the internet? Clearly it IS a massive problem. Of course it CAN’t be normal operation."

1976 CB 750-A X 2
1977 CB 750-A X 4
1977 CB 750-K
1976 CB 750 F
1981 CB 750
1966 Kawasaki SG 250
1981 KZ 750 LTD
1973 CB 350
1979 CM 185 Twinstar
1982 Honda XL 80
South of Eden (Kansas City MO)
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Re: My 1981 Honda CB750K Project Bike

shinyribs
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Welcome to the forum...finally! Ditto on what Tools said.
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Re: My 1981 Honda CB750K Project Bike

Hellbilly429
Thanks guys, glad to be a part of this forum. I just got my regulator/rectifier and alternator brushes in the mail, talk about fast shipping from powersport superstore considering i ordered the parts Friday night and got them today! I've been working on getting the bike into timing but now it seems to be running a cylinder or 2 down, i checked the spark on the cylinders i believe aren't running and the spark is good, I believe I might have fouled the plugs again because i ran it out of timing for a while so I will check those tomorrow. I am getting so close to having a complete working bike I can taste it! Then I hope to ride it and get a chance to paint the tank, I'm thinking gloss black with some skeleton hands wrapping around the sides of the tank, not sure if i want to keep the Honda emblems or not tho...
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Re: My 1981 Honda CB750K Project Bike

Piute


  Keep working on it Hell Billy
 You'll get IT,Black is great ya can always add to it ,I filled the emblem Mount on my tank then grounded the tabs off them may tape on later but have the chose.

                            1977 CB750 F2 Super Sport
<LET THOSE WHO RIDE DECIDE><RIDE TO LIVE-LIVE FOR JESUS> 
Native American from central Cal,  Kickstand UP in S.W.Missouri,
                                       
 
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Re: My 1981 Honda CB750K Project Bike

Hellbilly429
That's a great idea Piute, I didn't think about just sticking them back on later if i want to with some tape or glue, duh... Anyways, got a million ideas to do with the bike, mostly because I researched the hell out of it and found all the great things people do with these bikes and my long time dream of owning a sick bike. Think I went with a great choice of a bike to do that with.
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Re: My 1981 Honda CB750K Project Bike

Hellbilly429
Btw awesome bike man, real clean
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Re: My 1981 Honda CB750K Project Bike

Hellbilly429
Just swapped out my regulator/rectifier and put my new brushes on and slapped the right side cover back on, everything went together well and I cleaned all of the connectors with some electrical contact cleaner, waiting for the connections to dry before I put them back together.

I noticed before that the connections for the spark units look absolutely identical, and I am not sure if there is a specific harness that each one plugs into or does it not matter? I am wondering if maybe I swapped them on accident before when I was testing them with the multimeter and if that was why the bike isn't running right, but I am getting spark at all 4 plugs so I'm really not sure if it is important....

Got my new helmet today too!




Not bad for $80 huh?
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Re: My 1981 Honda CB750K Project Bike

shinyribs
Administrator
Red solo cup!!!!     Sounds like a good deal for a nice looking DOT helmetWhen you were talking about the connections on the spark units,are you talking about the "in" side or the "out" .The "out" side of the coils going to the plug wires shouldn't matter.As long as you have the 1-4 and the 2-3 coils going to their respective cylinders. If you have the "in" sides reversed it will fire the wrong coil at the wrong time. I may be way off base,I may have misunderstood your question.
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Re: My 1981 Honda CB750K Project Bike

Hellbilly429
Ha, I totally didn't realise I had the cups in the back of the picture, let alone the beer in the other one, we had some friends over for St. Patty's day and played some pong.

Anywho, I'm not totally sure I understand you or if you're not understanding me, so to make it easier I took some pics so you can see what I mean.



According to the repair manual these are the Spark Units



These are the connectors for the Spark Units that plug into the wiring harnesses that are in front of the regulator/rectifier. They are identical connectors with the same colored wires in the exact same locations for both plugs, so I just want to make sure that I have each harness going into the correct spot, or if that doesn't matter. The manual says nothing about which one goes where so not much help to me. Any clarification on this would help me a lot.
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Re: My 1981 Honda CB750K Project Bike

TOOLS1
Administrator
Be sure to put those to the right connections, or the engine could run backwards, and these bikes are very hard to ride going backwards.
TOOLS
P.S. I'm just pulling your leg. It does not matter which one goes to which.
Life is not about the number of breaths, you take, but the moments that take your breath away.
I don't have an anger problem. I have an idiot problem. Hank Hill
Never confuse education for intelligence.
Happiness is a belt fed weapon.
I just can't imagine what could go wrong.
No fire? No explosions? So whats the point of your story?
Those who are too smart to engage in politics are punished by being governed by those who are dumber. ~Plato
It couldn't be done, but the darn fool didn't know it, and did it anyway.
We all got problems. Ksharp
I like vintage bikes because they take me away from the clutter of technology that I work with everyday and back to a simpler time of mechanical elegance and simplicity.. "ninadm"
Darkwing Duck: The worst part of public transportation is the Public.
"That is awesome shit there" Re-Run
"Fear nothing, attack everything" Eric Berry
" Oh, you read that on the internet? Clearly it IS a massive problem. Of course it CAN’t be normal operation."

1976 CB 750-A X 2
1977 CB 750-A X 4
1977 CB 750-K
1976 CB 750 F
1981 CB 750
1966 Kawasaki SG 250
1981 KZ 750 LTD
1973 CB 350
1979 CM 185 Twinstar
1982 Honda XL 80
South of Eden (Kansas City MO)
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Re: My 1981 Honda CB750K Project Bike

Hellbilly429
Wow dude, that would've been nice to know before I test drove the bike, I put it in first gear and eased the clutch out and backed into my car.... Thanks for the clarification though, just figured I'd make sure that wasn't the problem before I moved any further and screwed something else up, Ha, thanks for the good laugh though
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Re: My 1981 Honda CB750K Project Bike

cdaiscool
In reply to this post by TOOLS1
Careful... there was a car that if you did that, the engine DID run backwards.


And when I was at a transmission shop, we had a high-end car at a sister company that worked on Ferraris, Lamborghinis, etc and there's a clip you put on the shift knob; if you put it on backwards, it WILL shift 100% backwards. 5 sp + reverse, 1st was where reverse was, 2nd was where 5th was, etc.


Looking awesome OP! Hope she runs soon.
Turbos, Hondas, 4-bangers, what could go wrong?

Fuelly

Shiny: [...] Considering the weather you've had to put up with I'd say you get an Iron Butt award and a Frozen Nipple trophy to go along with it. First time I've ever posted the word nipple... it ends here.
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Re: My 1981 Honda CB750K Project Bike

shinyribs
Administrator
Any two stroke dirt bike will do that too.If you stall it and it rolls backwards in gear it can refire turning backwards...ask me how I know...handle bars do not taste good
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Re: My 1981 Honda CB750K Project Bike

Redemption
Hi there, if you look at my thread its the 1980 cb750f bobber project you will find we have the same motor.

Ive become somewhat of a quick learned expert on this bike in the last 4 days or so. Those are the spark units and it wont make a lick of difference if their hooked reverse or not. What will happen though is that they could spark at the improper times and that could be real bad for the motor. Just have to make sure they fire at the right time via a timing gun.

If you need to know anything else I will be happy to explain. If theres something I dont know Ill shoot you straight. it was 4 frustrating days of tinkering and reading to figure it all out.
Riverside CA.

1980 Honda CB750f Rigid Bobber
1984 Yamaha XV1000L Soft Tail Bobber
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Re: My 1981 Honda CB750K Project Bike

Hellbilly429
Nice, I wanna know what car does that, funny how little things like that are so important.

Shiny Ribs, all I can picture right now is that baby in your picture wailing away while riding a dirtbike in reverse.

Redemption, I totally feel your pain about these bikes, and can see why most people are afraid to touch them, but I personally like the looks of the DOHC, and the price of the bike wasn't really worth bitching about either. I went from knowing like nothing about bikes and am now at the point where I know just enough to be dangerous But thanks for giving me another brain to pick for when it comes to questions on this bike and I am hoping maybe you'll figure out how to get the stock carbs on this to work with pods and an custom exhaust so you can let me know how to pull it off.
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Re: My 1981 Honda CB750K Project Bike

cdaiscool
Ask, and you shall receive!

http://www.cartalk.com/content/when-muscles-arent-everything?question

http://www.cartalk.com/content/when-muscles-arent-everything?answer





EDIT: I just realized you probably meant for the high-end car. I don't remember. I left that place in 2004 lol. But all they did was work on high-end stuff. Auto Sports Unlimited, in Zeeland.
Turbos, Hondas, 4-bangers, what could go wrong?

Fuelly

Shiny: [...] Considering the weather you've had to put up with I'd say you get an Iron Butt award and a Frozen Nipple trophy to go along with it. First time I've ever posted the word nipple... it ends here.
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Re: My 1981 Honda CB750K Project Bike

Hellbilly429
Haha, that is awesome dude, wishin I had a 2-stroke to test that on now....
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Re: My 1981 Honda CB750K Project Bike

Hellbilly429
So I dialed in the timing on the bike yesterday about as good as I can get it statically, but still not running quite right on cylinders 1 and 4, checked for spark and its good on both cylinders so I'm gonna go check the plugs one last time and make sure they aren't fouled again.
Got the new regulator/rectifier in and the brushes are all in, bike charges perfect now so I'm very happy with that. Headlight isn't working now though and I'm not quite sure why....
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Re: My 1981 Honda CB750K Project Bike

Hellbilly429
Headlight not working because the spring inside the switch isn't pushing the little metal plate out far enough to make a good contact with the plate that switches the headlight from low to high, lost the spring cause its so small!!! So I'm glueing on a spring that fits in there and hopefully that works, if not I will wire up a 3-way switch and call it good.
I think the choke is sticking on the bike, I pull it in to start it and it runs fine until its warmed up, then I push it in and it makes no difference, it revs up and crackles and pops like it's running really rich. I'm hoping its just the stupid choke.... lol.
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