Topic: It's a chopper, baby. My CB750K0 rebuild (warning LOTS of pics)

[Trad]

Man, this thing is clean. Really nice.

[mystic_1]

So after all this time making big changes on big things that are big and heavy and big, it was time to work on a few little things.



Plugged up the sump drain and the oil tank drains.

Made up some replacements for those hex spacers you've been seeing on the rear frame-to-sissy-bar mount points. 

Made these by purchasing plain steel (zinc plated) spacers from the local hardware store, cutting them down to the right length, and then drilling them out to the right size and tapping them on both sides.  This allowed me to use large bolts from the inside of the fender, and button-head fasteners from the outside, for a clean look.

I had stripped and painted the battery tray and the "electronics caddy sub-plate thing".  Started transferring the electronics to the new plate, pictured is the Oregon Electronics regulator that I was planning to run, i ended up having problems with this and threw the stock regulator back in just to get up and running.  I hear these guys have great customer service so I'll follow up with them eventually.


I'm also running the stock rectifier at the moment, will do a replacement on that as well at some point (or possibly go to a combined unit).  But, in the meantime, the old stuff works fine.



Battery tray and battery in place.



I had scored this replacement harness at yet another swap meet.  It's in fabulous shape and even still has the little part number tag still woven into the loom wrap.  All connections were cleaned up nice and bright.




Laid the harness into the frame and lashed it down with zip ties.



New battery cables were used,


and I'd made up a replacement ATC fuse holder to replace the single round glass fuse used on K0 bikes.



All wired up!



Since I no longer have a real headlight bucket, I'll be bringing all the front-end connections up under the tank and then putting the bundle-o-bullet-connectors where the coils normally go.  The coils will be dropped below the backbone rails so the wires will reach the plugs.

More to come.

mystic_1

[mystic_1]

I'd also stripped down and repainted the K0 seat latch assembly.  Purchased a new plunger since my old one had a groove in it approximately 46 years deep.



I was going to try replacing the main return spring with the one shown on the left, but that spring turned out to have to close a coil spacing, and wouldn't compress as far as needed.  Threw the old one back in for the moment, can come back and replace it later.

Managed to sneak in another chrome acorn nut here.










Mounted up the seat.




Lowered it slowly.




Click




mystic_1

[bigring]

You have mad skills.  Very impressive.  Thank you for sharing!

[mystic_1]

Bro, do you even Boot?!?






"... and this one time, in Band Clamp..."


New OE clamps and screws.




Slight difference.











OK, so those of you who have bothered reading this far, let me tell you this:  GET YOU SOME NEW CARB MANIFOLD BOOTS!!!!

The difference in these is like night and day.  I'd done the Wintergreen Oil thing, it works.  NEW BOOTS ARE BETTER!

While all of the above work was going on, I'd done the wintergreen treatment on my old rock-hard boots.  They softened up nicely.  I stuck them in a bag on the shelf and they sat there while I tinkered with the rest of the bike for a couple years.  Periodically I would check them, they stayed soft for more than a year but then started hardening up again, and in about three years were once again hard as a rock.  That's just from sitting on the shelf with zero gas or UV exposure.


The new boots slide into place with a satisfying 'pop' as they snap into place.  No need to crank down on the screws in an attempt to get a good seal.  Mounting the carbs was a real pleasure compared to the past.

I don't have any pictures of the actual carb install, but I get the bottoms of the carb throats started into the manifold tubes, then rock the rack up to level while pressing inwards and wiggling the rack up and down, side to side, slightly while pushing foward until the carb throats are started into the holes.

Then, I use some 24 inch bar clamps like these:



I hook the ends of the clamps over the intake sides of the outer carbs, the other end clamps down onto the front of the engine, with the bars of the clamps running across the top of the fins and next to the valve cover.  One clamp on each side, tighten each one a little at a time, working back and forth, and the carbs just pop on.


Speaking of carbs, I'd given them a good going through.



I opted to swap out the K0-style brass floats for the later plastic ones, just to try them out.  The jets were pretty recent so I just cleaned them up, besides I'd probably be making jetting changes coming up soon, more on that in a bit.

Otherwise no need for a full rebuild on these, although I did freshen up the polish on the float bowls, and cleaned up the exterior well.

mystic_1

[mystic_1]

I had also acquired a set of these:






BECAUSE, well, the bike had come to me with PODS mounted, and it was already set up to run well with them.  I ran them for years.  The bike never had an airbox fitted in all of the years that I'd owned it.  In fact, the previous owner had cut off the airbox mounting tabs on the frame!

Now, there are many, many threads on this form and others regarding the usage of PODS.  Less controversy exists over the existence of nuclear weapons, genetic engineering, and religion, combined into some sort of weird genetically augmented nuclear powered evangelist.  Who eats babies.



Sharp eyed viewers will have noticed by now that I even flirted for a while with..... VELOCITY STACKS!  DUN DUN DUN!




I flirted with them hard.



We took long walks on the beach together.



We shopped for a dog together and shared ice cream.










BUT, after many many long conversations with members here including the inimitable TwoTired, I decided NOT to go with the stacks.


Or the pods.


In fact, I did this:



A little faded but servicable. 


Mocked up.



A bit of cleaning, some coats of Krylon Fusion, and one new filter later...








... and then it looked like this!



mystic_1

[mystic_1]

"A stock airbox?  On a chopper?" you say?


Yeah the stacks look awesome.  Pods look bad ass.  I love the way they look.

BUT

The fact of the matter is that on a stock motor like this, velocity stacks very little, and neither do pods.  In fact, by reducing in intake tract length,   one is reducing the effective vacuum seen at the carb venturi.



Since you're seeing less vacuum at the venturi, now you need larger jets so that you end up drawing the same amount of fuel-to-air for a proper mixture.  Changing the intake filtering doesn't make the engine more able to swallow air, that's all a function of the piston and bore dimensions, valve geometry, and cam selection. 

Combined with all of this, I also never liked riding in the rain with pods, because I was always worried about the water I was surely ingesting into the motor.  I change the oil pretty regularly, but still I didn't like it.


SO, on went the stock airbox.  I'll need to jet down the mains a bit and adjust needle positions once I got the bike running.

I gotta say too, I kinda like how it looks, no more awkward open gaps at the leading edge of the side covers. 

At some point I'll source a reproduction K0 airbox, and for now the pods and stacks live in the drawer of my nightstand, next to... other things. 

mystic_1

[mystic_1]

Mounted up the instruments and handlebar controls.

Used an old switch housing to mark and then cut the bars for the internal wiring, then laced up the control pods.





NOS Barnett extended throttle cables.




Got the battery charging up while I worked.  Cheepo Walmart battery.



New mini speedometer with integrated LED indicators.  Matching mini tach.




The mounting brackets on the new instruments bolt right up to the mount points on the triple tree (K2?).  Made up a little plate to go between the instruments and keep them in place.  Acorn nuts, naturally.









Worked out a schematic for the new indicators.






Had to do a diode conversion of course for the LED winker indicator.  Fortunately I keep a bag of diodes laying around, for just such emergencies.  I used 1N4004 diodes, rated at 400V forward voltage by 1A.  More than sufficient for this application.








All wired up!

Later on I came back and changed out the backlight bulb for the tachometer with an LED replacement, that got the backlight color closer to the speedometer although it's still not perfect.


Speedo and tach cables are stainless braided lines from Yamiya.  Great fit and finish!


In this picture you can also see the acorn nuts I used on the bottom of the forks.  I'd also decided to throw something in to fill the front fender stay holes that I wasn't using.  These are actually bullet license plate fasteners, it turns out that their mounting studs were metric and threaded right in to the forks.



Repurposed this mounting clamp from an old windshield mount...


... turns out it makes a great cable clamp for the speedo cable.  Does not clamp down on the line too tight, so no binding.  In fact, the line is free to move through the bracket with just some slight drag.  I was pretty happy with this, always like to reuse and repurpose parts.


Same item on the wife's Shadow.


Hides nicely under the tweak bar.  You can see little sections of rubber hose that I added to the lines to prevent the braided outers from chafing the chrome.



Starting to shape up!







Turn signals are mini bullet incandescent units from Wyatt Gatling.



In this pic you can also see more of those license plate fasteners that I'd used on the fork lowers.  Rear signals replace one of the bolts that hold on the license plate bracket.







Also fitted a new rear brake switch.



More to come....

mystic_1

[mystic_1]

Right, let's get some front brakes on this thing!

Master cylinder was disassembled, stripped, and polished.












New rebuild kit installed.  Also replaced stock screws with chrome allen button heads.









All-new Russell braided brake lines, with attendant fittings.





New banjo washers, of course.



Found a chrome button-head style banjo bolt for the master cylinder connection, since I wasn't going to be using the dust cover.





I'd decided I wanted to keep the hard line at the caliper, as opposed to running the line straight to the caliper as others sometimes do.




Caliper all painted and polished up.  New piston seal, caliper bolts, and Speed Bleeder ready for installation.










Snuck in another acorn nut on the caliper adjuster bolt





Using the stock splitter for the front brake switch.  Similar to stock, the line coming from the master cylinder has a straight connection, then the line going to the bottom has a 45 degree bend. 







OK so here's the magic piece that you need to join AN-3 brake lines to the stock hard line, Russel 641471.  This converts the AN-3 brake line end to fit the hard line's "Japanese Metric Inverted Flare".



By a happy coincidence, when fully installed, the adapter sits just inside the brake line guide that's bolted to the fork leg.  By removing the rubber ring from the stock brake line, I was able to reinstall it here for a super-clean installation.  After bolting everything up the rubber piece slides forward and snaps into place.








Ready to rock.





mystic_1

[mystic_1]

So, in case anyone else looks for this information, here's the details on the braided stainless brake line components I used:






The top line, going from the master cylinder to the switch splitter, was Russell 657042, an 18" line with a 10mm Banjo on one end and a AN-3 connection on the other.   Stock bikes will of course use a shorter line here.  To size up the lines, I used a piece of solid copper house wiring, routed the way the line would be, and then subtracted an inch to account for the length of the AN-3 adapters.

I wanted to use a line with a fixed end rather than the AN-3 replaceable connection, because the fixed connection is simpler and cleaner looking to me.


To this, I added a Russell R4047C banjo fitting (straight).




The lower line is also 18" and has AN-3 connections on both ends.  Again, stock bike will take a shorter line. 


For the top end, I used Russell R4055C, a banjo fitting with a 45 degree bend.


 

And for the lower end connection to the hard line, of course, the 641471 Japanese Inverted Flare adapter.


cheers
mystic_1

[mystic_1]

So I needed to work out the headlight thing, wiring-wise.

Decided to drive the headlights off of relays which are fed straight from the battery via separate fused connections, thus taking most of the load off of the handlebar switch, and allowing me to use larger-gauge wiring.

The plan is this:



Decided to put the relays in the tool tray right next to the battery, so the fused power leads to the relays were nice and short.  These are hooked in at the positive battery post.


These are standard SPST automotive relays, from the corner store.




Ran the power leads for the lights up the right side of the backbone and then out individually to the lights.


I normally dislike using crimp-on connectors like this, but it's what I had handy at the moment.  I will come back at some point and replace these with nicer solder-on spade connectors.


Cleaned up the wiring





more to come...

mystic_1

[mystic_1]

Next I gathered up the collection of lights I'd mentioned earlier and picked out the two best shells.



Nasty old 6V lighting and crappy reflectors.  Nice glass, though.


These are bayonet base bulbs, similar to 1156 turn signal bulbs, in that the side locking pins are the same heights, but these were dual-filament.






So, I needed better internals for these.  I sourced a couple of "Blazer" brand H3 "fog lights" from Walmart for $20.  These are 55w bulbs, so a little hotter than stock.


The key here is that the reflector assemblies in these are nearly the same size as the ones from the lights I had.

So, I....


... and then I cleaned them up a bit ....


Then the reflector assemblies from the new lights popped right in!






The glass then sandwiches the flange of the reflectors into the old ones.  The rubber seal around the new reflectors seal the glass to the old housings, for a pretty tight seal.


Added the bezel...




And mounted them up!


The top light already had a hole for an indicator light.  For now I installed a red one that I had handy, but there's no light behind it at the moment.  I'll come back and replace this with a blue LED at some point.



Also, in my configuration, both the low beam and the high beam are 55w bulbs.  The low beam is aimed lower so it hits the ground in front of the bike, but the high beam is literally aimed higher so that it throws out much further.   In my case I chose to use the upper light as the low beam, because I think that looks better, but that means I'll need to run another wire into that shell to drive the high beam indicator.  No big whoop.












Now, as to light patterns, the lights I bought claim to throw a 10º vertical by 130º horizontal beam, but that's with the stock lenses.  Also these are built as fog lights and not as headlights, so the pattern doesn't have the cutoff you'd like to see in the pattern to avoid blinding other drivers.  Aside from that, they throw a decent amount of light similar to what I was running before, which was a 4x6 sealed beam headlamp (40/60?) in a dune buggy housing.

So I fully realize that I'm not being as kind as I should be to fellow drivers.  I kept the low beam aimed fairly low (probably too low) and haven't really been riding much at night so far.  I'd like to come back and improve the light pattern somehow at some point, perhaps by adding a shroud near the bulb to limit light thrown up and to the left.

mystic_1

[rickmoore24]

The lights came out quite nicely Mystic, well done and duly noted.

[mystic_1]

Thanks!

At this point I was able to finalize the exhaust system.  The connector pieces I'd made allowed me to slide things around a bit before clamping them up to adjust length and rotation a little.








The hanger straps are 1/4" bar stock, very sturdy.  Small offset bend to line things up.




Here's how the muffler plate sits, this looks unstable but only because the two bolts on each muffler help keep things from moving around once it's all bolted up.  Once it's all assembled it doesn't move at all.











All mounted up.



I came back later and added some little chrome heat shields to cover up the connector pieces I'd made to go between the head pipes and the mufflers.



Ready to rumble.



mystic_1

[Desert-SOHC]

Nice work, I really like your concept of the "70's" custom SOHC.

[rickmoore24]

Very cool, I'd love to hear it. Maybe a video when it's all buttoned up? 

[budman]

You are one documenting son of a gun.

[SOHC4 Cafe Racer Fan]

I love those slash cut pipes.

[mystic_1]

Thank, gents.

I was pretty pleased with how the pipes turned out.  The sound is OK for now, but I'm meaning to pull the baffles out of the mufflers, modify them a bit, and pack the mufflers.  Right now the sound is OK but I think if I open them up a bit and do a bit of tuning they'll sound great.

I'll try to shoot some video on the soon side.

mystic_1

[rickmoore24]

Sweet, looking forward to it! Rick.

[mystic_1]

I should mention, also, that this was all buttoned up last summer, and I'm just playing catchup with the build thread now.

I'm actually up for Bike Of The Month this month, if you haven't voted yet

http://forums.sohc4.net/index.php/topic,155984.0.html

mystic_1

[mystic_1]

Dug through my gopro footage and managed to put this together.

Not the best video or audio, and just a quick run around the block.

[SOHC4 Cafe Racer Fan]

Nice clip. The bike sounds smooth.

[rickmoore24]

Sounds good and runs good!

[mystic_1]

So the rest of the story is pretty easy to tell.

Buttoned up the fuel system using new OEM fuel line.  The bike had always had 1/4" fuel line fitted since I'd bought it all those years ago, finally decided I wanted the correct line and routing.

As with so many other things OEM, this was a joy to work with compared to the automotive line I'd been using all this time.



Routed the lines forward from the inlets through the holes in the carb stay plate.




Routed them over to the left side...


... and added a little brass Tee for the connection to the single-outlet petcock (using a later K tank and petcock).



more to come...
mystic_1