Quebec 1981 CB750K

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Quebec 1981 CB750K

deskinthewoods
Hello All,

I bought this bike in 2012 for $800 CAN. It ran but not well...



The first thing I did was strip and paint the tank, finding bondo UNDER the factory red paint.
I used copper, then brown, then a light spray of black. Rubbed down the high points to give it an aged copper look.




Baffles in the exhaust were rusted out, so I made new ones from some brass pipe and bits and pieces.

 Yup, stainless steel scrubbies!!

more later...



1981 CB750K
Wakefield, Québec, CANADA
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Re: Quebec 1981 CB750K

deskinthewoods
Installed K&N pods (I know, I know!),


swapped in larger jets



and pilot screws backed out to 3 1/2 turns.

Cleaned the carbs and syncronized them.


Took her out and she ran pretty well except for acceleration and deceleration (back firing) and anything over 4000rpm

Decided to build a new seat 'cause I can do that!


and installed a "Superbike" handle bar that a friend gave me.

...Read about taping up 75% of the pods to restrict air flow. Better but still a lot of hesitation on acceleration...cleaned the carbs again and bypassed the air cutoff valves and removed the vacuum assist petcock as per someone's advice on one of the forums (Frank/mtspot?), and found all the accelerator pump ports were clogged so blasted them clean
...no more acceleration hesitation!!!

Replaced tape on pods with brass.

 By now it's mid October 2013 and getting chilly. The last ride of the season I got home to find an oily fluid leaking out the exhaust joint (PO had attached the pipes with hose clamps after doing some surgery on them ). Thought this could be something needing attention inside so I ordered a gasket&seal kit and new rings and committed to tearing down the top end over the winter. Now, I'd never done anything more than change a flat tire or do an oil change but I'm pretty handy generally so I figured it would at the least be a learning experience!
1981 CB750K
Wakefield, Québec, CANADA
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Re: Quebec 1981 CB750K

deskinthewoods
This post was updated on .
After man-handling the engine out of the frame and onto my workbench, I started the tear-down in January 2014.








The valve cover grommets mostly cracked and done


I snapped one cam cap bolt , drilled it out and repaired it with a helicoil.




The front cam chain guide was broken,

got a new one


I started in on lapping the valves and found a bent one, exhaust on #2 cylinder.
 Ordered a new one.

I installed new valve seals



and re-installed all the valves.




1981 CB750K
Wakefield, Québec, CANADA
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Re: Quebec 1981 CB750K

deskinthewoods
This post was updated on .
Removed the cylinders, removed and cleaned the pistons, and found a broken ring on #2.




Replaced the rings, cylinder o-rings, gaskets, and o-rings on the studs




Honed the cylinders lightly as they were in very good shape and reassembled the engine. I measured valve clearances and swapped around/out shims accordingly.


Replaced the oil drain bolt and oil pan gasket and cleaned the oil screen and pan.


Reinstalled the engine in the frame!


(hmmm, must have made the brass covers on the pods later...memory is going )
1981 CB750K
Wakefield, Québec, CANADA
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Re: Quebec 1981 CB750K

deskinthewoods
In reply to this post by deskinthewoods
Oil in and electrical all checked out. Compression an even 115 psi on all cylinders cold.

It's March 2014 and still snow on the ground....think I'll make some new side covers.



Polished up the engine parts I could pull off


Installed new sprokets and chain

 and a new rear tire


1981 CB750K
Wakefield, Québec, CANADA
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Re: Quebec 1981 CB750K

deskinthewoods
And a bunch of other stuff...
   - rebuilt the exhaust pipes to straighten and shorten them, rebuilt the baffles longer, painted the pipes black and wrapped them.
   - removed the center stand because it dragged (lower pipes = lower center stand )
   - bought new indicators and tail light (mounted down on the left on a homemade bracket) (yay ebay!)
   - bar end mirrors
   - led bulbs in the indicator and tail light
   - copper and leather homemade grips
   - cut back the rear fender and mounted it on the swing arm
   - cut off the rear of the frame and built a cantelivered, removable rear seat on a leaf spring
   - last week the throttle cable snapped so I replaced both of them

As of today, it looks like this:
 
1981 CB750K
Wakefield, Québec, CANADA
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Re: Quebec 1981 CB750K

Re-run
Administrator
Very nice. The seats are really unique. Don't know how well the passenger seat will work being shaped like that, but it is neat looking nonetheless.

And at least you used K&N pods! Those at least give you a fighting chance of having the carbs work.
The ride IS the adventure. The destination is just to get gas!
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Re: Quebec 1981 CB750K

TOOLS1
Administrator
In reply to this post by deskinthewoods
That thing is looking SteamPunk.
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: Quebec 1981 CB750K

deskinthewoods
So far I have had only one passenger, my 15 yr old step-daughter. She said it was really comfortable but she was also hanging on pretty tight, her first ride ever, and we did a country loop with lots of turns and a few bumps. I've never had a sweaty back after a ride before! The seat is the same pattern as the front seat without the, um,... pecker shelf? It actually has a pretty good slope towards the front when you sit on it and the padding squishes down.

The pods work great. I put some deflector shields on the outer two as I got some sputtering in strong cross winds. Figured that out last fall on a cold windy day when I tucked my knees into the engine for warmth and she took right off.

Definitely going for a bit of a punk look.

1981 CB750K
Wakefield, Québec, CANADA
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Re: Quebec 1981 CB750K

deskinthewoods
I went with the pods as the PO had put crap one's on already, though he still had the airbox  but had lost the filter cover.
1981 CB750K
Wakefield, Québec, CANADA
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Re: Quebec 1981 CB750K

shinyribs
Administrator
You did a lot of really nice, unique work there. Good work! But you have to tell me how you stamped the lettering on those side covers. Leather stamp,maybe?
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Re: Quebec 1981 CB750K

deskinthewoods
Well, I have have access to a laser engraver at work that can, among other things,  make rubber stamps. Instead of the rubber, I used a piece of plexiglass and then hammerred the copper over it by hand using a piece of pine to get around all the detail. Took about an hour of tapping away for each cover.

It's the figuring out how to do stuff like this that really turns my crank!
1981 CB750K
Wakefield, Québec, CANADA
Maz
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Re: Quebec 1981 CB750K

Maz
Now that is dedication and an eye for detail! Top job

Maz
'76 CB500T
'75 GL1000 'Wing
'79 CB750L
'90 FJ1200
'93 GS500E

In a little place called Bexley, Kent, UK (Just south of London!)
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Re: Quebec 1981 CB750K

Truck
In reply to this post by deskinthewoods
Can you make bigger Plexiglas? That would look cool mounted on a wall with some LED's behind it!
It's only illegal if you get caught.

If at first you don't succeed, use more lighter fluid

95% of Harley Davidsons ever made are still on the road... The other 5% made it home.

New Baltimore, Va '82 CB900c, 1980 CB985F/K 'Mutt"
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Re: Quebec 1981 CB750K

deskinthewoods
There are a couple guys at work who outfit trailers, as a hobby, for bikes but also fitted out for camping when the bikes are out, fold down beds, microwaves, sound systems, wifi, blah,blah,blah. I've done up some led light switch panels for them. Very cool in a disco kinda way!
1981 CB750K
Wakefield, Québec, CANADA
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Re: Quebec 1981 CB750K

cblover
Great work in rebuilding the bike. Love the idea of using other inexpensive material to add some bling into it.
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Re: Quebec 1981 CB750K

deskinthewoods
Yes, it doesn't have to be a bank-breaker to have something fun going on!
1981 CB750K
Wakefield, Québec, CANADA