My 1975 CB750 K5 Cafe Project... LOTS OF PICS!!!

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03-03-2012, 06:28 PM

K'netic

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My 1975 CB750 K5 Cafe Project... LOTS OF PICS!!!

This is a copy of my thread on SOHC4.net, a forum dedicated to Honda's single cam four cylinder bikes.

I'll post a little bit about me then get right into it.

I started getting in to old Honda 750's about 3 years ago after I wrecked my first bike, a CBR954RR.

And after 3 long years of wishing I had one, I found one locally. The price was right so I just couldn't pass it up. Trading two guitars and $140 later I picked up a 76 Super Sport with 35k on the clock.

I didn't have any time to work on it so it sat in my garage for a couple months... Then I sold my drift car (a 97 Nissan 240SX)

Well, suddenly I had money burning a hole in my pocket.
I started looking around on Craigslist and came across another great deal I couldn't pass up. A 1975 K5 for $250.
A 6-hour ride later and she was in my garage next to the F1.

I had some Clubman bars laying around for a few years so I dug them out and threw them on the K5 to see how it looked.

My garage was a mess, so I cleaned it up, and that only served to motivate me further.

After I finally got to see it taking shape I went a little crazy and started tearing things down...

And before I knew it, I was looking at this...

After a quick clean up I got all the parts together and started planning.

The front caliper was seized half-way on (same as the F1). These wheels would probably need new spokes, bearings, and maybe even new rims. At that rate, I might as well build a new set of GL1000 wheels and forks so I can run dual discs in front and single disc in the rear.

The frame is stripped completely bare now. It's ready for sandblasting, some slight modification, and then some powdercoating.

Bruised the hell out of my arm lifting this sucker onto the workbench.

There was a ridiculous amount of grime built up in the front sprocket housing. It seriously looked like the previous owner hand mistaken it for a dirtbike. I had to break it loose with a screwdriver and a hammer just to get the chain off.

Everything under the valve cover looked pretty solid.

I'll re-gap the valves, but that's nothing I wasn't planning on doing anyway.

Even the spark plugs looked half-way decent.

Not sure what condition this oil tank is in. When I tried to remove the near-side hose the neck started bending.

It doesn't matter too much though; I'll be making a custom reservoir to replace it.

Carbs looked pretty nasty...

After I had everything apart I started looking at the F1 and debating whether to keep it or not.

I'm trying to figure out what forks/brakes are on this thing. They're obviously not original.

The coupler on the top of the fork causes clearance issues with putting clubman bars on it.

I had these gauge visors left over from my 240 build and I had an idea.

Turn them around and integrate them into the backside of a fiberglass headlight bucket, and poof! Instant gauge mounts.

Well, the other day the first round of parts showed up.

And the first order of business was rebuilding and cleaning up those nasty carbs.

So,

BEFORE:

Annnnnnnnd,

AFTER!

I've already talked to Benji about making me a "Dimpol" style carbon fiber tank and 2-seater seat (and maybe a carbon front fender to carry the theme through to the front).

So that's where things stand right now.

I'll be sure to keep this thread current whenever I do something new.

I'm working on securing access to a sandblaster so I can blast pretty much every metal piece on the bike and get everything ready for powdercoating.

^^^ That was as of Christmas day last year.

vvv Here's the latest update as of today...

First off, I've decided that I don't need two of the same bike, so I traded the F1 for a Toyota 2JZ engine. I think it was a good deal, since I hardly had any money wrapped up in the 76. Here's what the new owner has done with it so far...

Anyway, let's get into the update. We'll start with the new additions in the parts department.

My new headlight showed up from Taiwan. I bolted on the turn signals (which were the right thread pitch to fit in the side bolts) and test fitted the visor I got from Carpy.

The housing is metal and the construction seems to be really nice. The "bulb" has plastic rather than glass for the lens. The main reason I got it is because it uses an interchangeable H4 size bulb so I can run HID's on the bike. I haven't decided on the color temp I want yet. Either 3000k Yellow or 6000k Diamond White. As far as wavelengths go, 3000k has more actual light output, plus it would help me stand out to other traffic at night (and we all know the more noticeable you are at night, the safer you are).

Next I got in my new seat from Vietnam. It's mounted to a brand new seat pan and the fabric and stitching seem sturdy.

The only thing I don't much care for is how wide it is and how the foam on the edges of the seat are at a very hard right angle, which makes it a bit uncomfortable on the thighs.

After looking at it and trying it out for a couple months I've decided to use it just to get the bike back on the road. Oncel I can afford to order one of Benjie's 2-seaters I'll sell it.

I got tired of looking at the F1 sitting there all stock so I slapped the bars on and played mix and match with the seat and tanks.

Then I got REALLY bored and decided to spray the F1's tank gloss black (no prep besides wiping it down) just to see how it looked.

Since I didn't have the money to sandblast the frame I had been going to town on the frame with a wire brush and some degreaser. I also decided that the cost of powdercoating the frame was going to be too high so I got her all cleaned up and gave it a few coats of heavy duty gloss black enamel.

I'm pleased with the way it turned out.

Since I was going to be doing a lot of painting, and since it's winter, I decided to build a make shift paint booth in my garage so I don't get over spray on everything in there. Been there, done that; it sucks.

It's just made with some 2x2's from the lumber yard, some painters plastic from Walmart, staples, and paneling nails. I cut triangles out of some old paneling to make the corner braces and used two long nails to make the hinge for the door.

I used an old air conditioner filter to make an intake and exhaust vent.

Then I used some ratchet straps and my old futon frame to make a height-adjustable rack/table to hang the parts from.

I put a small space heater inside so now, even when it's 45 degrees in the garage, the paint booth can get up to about 70 degrees in 15 minutes.

Now that I had my paint booth it was time to strip down the K5's tank and respray it. Since aircraft stripper wasn't doing a damn thing to that old paint I gave up and stripped her down to bare metal using the wire wheel on my bench grinder. By the time I finished I wished I'd had the grinder in the paint booth. The dust from the old paint was EVERYWHERE.

After some prep and a coat of primer, it was ready for the new color; Satin Olive Green.

Thank God for filtered breather masks. I'd probably have died otherwise.

Then it was time for the headlight.

I got sick of how stinking cold it was outside and how much it was costing me to run that damn propane heater so I decided to bring the project inside. My new tires had shown up so I couldn't help myself; I started wedging random parts together to mock things up and see how it would look.

Wouldn't it be cool if it could actually be THIS low and still function?

Just trying to see how it will look at normal ride height.

I found my old jump box so I'm using that as my power source to make and test the wiring harness. I also wanted to see how bright the turn signals were. The answer is: pretty damn bright.

You'll notice the clutch lever is backwards. It's just for mock-up purposes. I'm going to make reverse levers for the bike eventually, I just wanted to mock up the concept to see how it felt.

It actually feels a little better than normal levers. This way you can pull the lever all the way in with your index and middle fingers and not crush your ring/pinky fingers.

The bike has been sitting like that for a while, since I'm broke as a joke at the moment. I was going a little stir crazy so I thought of what else I could do for free.

To start with I did what I've been dreading for a while. I started taking the wheels apart. And I can tell ya, when you don't have the right tools, it is a MAJOR pain in the *** to unmount a tire from a rim.

Unfortunately, the rim was about as rusted as I expected it to be. I can't tell yet if the rust is bad enough to compromise the structural integrity of the rim. Thankfully, I've recently gained access to a sandblaster so as soon as I can afford to buy some media I'll blast the rims. Then we'll know if I need to get new ones or not.

I still need to get the rear wheel taken apart to see what condition it's in. The spokes seem to be in pretty good condition with just a little surface rust. A new set of spokes and nipples on eBay is about $75 so I'll probably just get a new set (unless anyone has some horror stories about eBay spokes).

I also got my new exhaust in from Carpy.

I made sure to install the baffle right away. It was quite a pain getting it in because the clearance was so tight. But I'm ok with that. At least I know I won't have to worry about it rattling around in there.

Three of the retarded philips head bolts that hold the exhaust primaries in the head decided to strip out on me (my philips bit actually broke off in one of them). After trying every bolt extractor I could find I finally gave up and took the motor to my friends' shop so he could weld a stud onto each one and back them out.

As you can see, the new exhaust seats directly to the block with it's own flanges so the old ones had to go.

Some of the next things on my to do list are to take the front caliper apart and rebuild it (if necessary), get all the parts together that need to be blasted, then start the wiring.

On the topic of blasting, can anybody lend their expertise on what types of media I should use for which parts? I've heard it said that I should soda blast the motor to clean it up rather than use sand. Is soda blasting efficient at getting all the caked on crud off parts like this?

Obviously, when I'm blasting the motor I should make sure all holes (exhaust/intake ports, etc.) are well plugged so no media gets in, but are there any other guidelines I should follow when blasting it?

Well, moving on...

I've decided, after looking at it a lot, that I don't really want to go with the satin green I sprayed the tank. The whole "army theme" bike has been done many times before and it's just not really my style.

Instead, I'm going back to what I've always done. All black with just a hint of anodized purple. So many of the details of this bike are going to "modern" that I figured a not-so-70's color scheme would work with it pretty well.

Since the F1 is gone, I've changed the plan for the K5 dramatically.

When you're building something like this, your individuality shines through in the details. So today I'll share with you the way I plan to make this bike "my own".

As I've already stated, black and purple is going to be my color scheme (99% black, 1% purple), I also mentioned my "Reverse Levers" idea. The plan is to try out some reverse-mount levers for time trial cycling.

Then route the front brake cable to this cable-operated master cylinder.

Since the factory levers are mounted to the controls, I'll be getting aftermarket universal controls. It will probably be a combination of the throttle/start/killswitch combo from a CBR and this universal unit from K&S for the left side.

I plan on updating all of the electrics, starting with making a complete replacement for the factory harness. After that, it's basic things like new relays, new one-piece voltage rectifier, new brake switches, and replacing the battery with a new dry-cell unit from Ballistic Batteries. The other thing I don't much care for are the analog gauges. The plan is to replace them with modern aftermarket electronically controlled units. I have a 3.5" speedometer and tachometer that I was planning to use in my old 240sx before I sold it. They will be a perfect fit for the bike.

The way I figure, it shouldn't be too hard to create the electronic signal necessary to run the gauges. The tachometer is pretty straight forward. Connect the signal wire to the negative side of the coil and use a signal filter to clean up the noise and get an accurate reading.

The speedometer is a bit trickier, but still relatively easy. The speedo can receive input from a basic universal speed sensor that creates a pulse every time a piece of metal passes in front of it. All I would need to do is mount the sensor on the swingarm and point it at the teeth of the sprocket. It should work in theory, but it always seems that you always need a few modifications between theory and reality. I might even add a matching oil pressure gauge if I can find a clean and convenient place to mount it.

After I get the gauges functioning properly it shouldn't be too hard to machine a way to mount them and seal them so they're water resistant. I also found the old Viper alarm I'd planned to put on my 954, so that will be going on the bike when I sort out the wiring.
That takes care of the electrical system.

As far as performance goes, I'm not going to do anything like boring out the motor or using any power adders. I've had a fast bike before, and there's not much I could do to this thing to make it compare to my old 954RR. The point of this bike is to turn heads and be something I can ride whenever I want. It'll be quick enough the way it is.

I'll check the valve gap and all other regular maintenance stuff and dial in the carbs to work with my intake/exhaust setup, but other than that, it'll remain stock.

The motor is going to get a coat of black engine enamel after it gets blasted. And I mean the WHOLE motor, not just the top end. Hell, I might do the carbs too. It's also getting a shiny new set of bolts for the engine case.

My fork ears are pretty well shot and I'm having a hell of a time finding another pair. After I painted them everything looks ok from the front and side.

But the rust has eaten away the back, as is typical with this style of ear.

The forks aren't in too bad of shape, but you can see how pitted the top of the fork tubes are from the rust that accumulates under the fork ears.

I'll eventually replace the fork tubes with new ones, but these still work just fine so I'll put new seals in them and run them for now.

Since riding season is creeping up on me, this is the basic plan for right now:

Get all of the parts blasted
Spray the motor and all other parts that won't be getting powdercoating
Get new spokes and reassemble the wheels/mount the new tires
Rebuild the front caliper/get new pads/shoes
Make the new wiring harness and make it work with the stock controls and gauges (for now)
Get a new chain
Get the motor put in and sync the carbs

Then get ready to ride!

I hope I didn't bore you guys to death with this lengthy update. Maybe someday my rantings and ravings will be of help to someone who's getting their first project together.

Hopefully I'll have a job here soon and I'll be able to get going with this project again. I'M DYING TO RIDE!!!

Once I have income again I'll try to update this thread more often.