Topic: CB750 K4 Build - The Cafe Tracer

[budman]

Howdy.  I signed up a couple of years ago after I was given a '74 basket case.  The bike was in horrible condition, but I see its potential.  Been itching to dive in ever since, but time and circumstances didn't allow until today.  I got the bike tore down to the frame and all the tabs I don't want removed.  The company I work for manufactures abrasive blasting (surface preparation) equipment so I'll get the frame blasted and primed in the next few weeks.  I don't know how long it's going to take or how much it's going to cost.  I've got a pretty good idea of where I want to take it.  For now here are the first photos.

[budman]

Today's progress.

[budman]

Spent the weekend breaking down parts and degreasing.  I brought the sliders into work this morning and hit them with some sugar sand in the blast cabinet.  Since I'm not going to run a front fender I shaved the right slider.  They're getting painted black.  The blasted surface will help the primer stick.  Back in my autobody days we used to use this black etching primer from Sikkens.  I don't know if it's still available, but that stuff stuck to everything.  Wish I had some.  I'm not sure if I'll use etching primer or epoxy primer at this point.

[SOHC4 Cafe Racer Fan]

The media blast should provide a clean and etched surface suitable for paint. Alternatively, I recommend powdercoating the legs for greater durability.  I PC'd my fork legs and that saved me a huge headache when I had a small brake fluid leak at the caliper.

[budman]

I considered powder coating, but I'm an old painter from way back and I like doing everything myself.  Whenever I have someone else do stuff like that for me I'm never quite satisfied with the outcome, plus I enjoy the work.  A good quality acrylic urethane paint will do it for me.

[SOHC4 Cafe Racer Fan]

Considering the owner and builder is a painter, no problem! 

[Stev-o]

Welcome from Lake Travis Budman.  Looks like you made quick work of the tear down.

What is your vision?

[budman]

Thanks, Stev-o.  The engine was already out of the bike so the rest of the tear down went quick.  I want to build a cafe/tracker sort of hybrid thing.  Lots of blacked out parts, but some chrome and aluminum too for contrast.  I plan to keep it bare bones and very basic.  There's not much of the bike that's usable so pretty much everything is getting replaced.  So far the only thing I'm using is the frame, the swing arm, the front rim and hub, the fork sliders, maybe the front brake caliper, which is the only thing I have left to tear down minus the engine.  Everything else is toast.

The engine is in pieces. I think the cylinders are good, but needs new sleeves. I think the head is probably salvageable. The cases had water in it so until I tear it apart I don't know what's good. I'll probably keep the engine mostly stock except for the ignition and air intake. Just dress it up. Problem 4 into 1 exhaust.

I'll be fabbing an oil tank and battery box with  custom side covers.

I've got something unique planned for the seat and cafe style rear section.  Until I pull it off I don't want to let the cat out of the bag.  Paint will probably be mostly rootbeer brown with custom touches.

That's the plan...at least for today.

[Stev-o]

Sounds like a plan.  Let me know if you need engine parts, I have many spares and will let go of them cheap.

[budman]

You just might be hearing from me Stev-o.  It'll probably be a while though.  I'm going to be concentrating on the chassis.  I'm going to leave the bottom end together for now while I do some mock up and fab.

I am looking for a rear rim though.  The one that came off the bike was a 16" rim and the hub was in poor shape.  I scrounged what I could from the wheel.  I already have a replacement hub.  I just need an 18" rim.  I know I can buy a new one, but I'd rather find a used one because I'm going to blast and paint it.

I got the sprocket carrier and the front hub blasted this morning.

[budman]

I got the front rotor cleaned up this morning.  I'm going to have the guy who gave me the bike, who happens to be a machinist, resurface it for me...he said he could, anyway.  But before he does that I'm going to drill the rotor.  I knocked out a 3D model to get some ideas.  I'll probably mess with it some more before I decide what type of pattern to go with.

[SOHC4 Cafe Racer Fan]

Bud,

If your machinist will resurface the rotor, he can probably do your drilling faster.  Otherwise, you'll be spending some time on the drill press.  You may also want to include slots as well as holes, since he can cut those.

[budman]

He could probably drill it faster, but he's so bogged down with work and he's getting ready to move his shop.  I'll have to go over there on a Saturday and watch over his shoulder just to get him to resurface the thing.  He would want to write a program and put the rotor on his CNC mill for the grooves.  I don't want to bug him for that.  I've got a decent drill press at home.  I should be able to handle the drilling part.

[calj737]

I hope you've got good bits and remember to chamfer the holes....

[budman]

I hope you've got good bits and remember to chamfer the holes....

Yep and yep.

[Steve_K]

If you have a good chuck on your drill press, I would use stub drills.  They are shorter than regular jobber drills and you would not have to center drill holes first.  Slow speed and some cutting oil and you are good to go.
Steve

[budman]

Got home and roughed out a couple of side covers from some aluminum sheet.  Still lots to do.  I need to put a little bend in them to follow the contour of the frame.  Shouldn't be a problem.  Hope to get the new mounting tabs welded in place next week.

[Stev-o]

You dont have duct tape?   HA!

[budman]

I ran out.

[budman]

Side cover concept.

[Stev-o]

like it

[SOHC4 Cafe Racer Fan]

Side cover concept.

Good proportions.  What are you making them out of and how are you mounting them??

[budman]

The covers themselves are either 14 or 16 gauge aluminum sheet metal.  I forget exactly.  I'm going to make the mounting tabs out of 1/4" steel plate so I can tap them.  The tabs will get welded to the frame obviously.  I ordered some fine thread, stainless steel button head, cap screws to mount the covers with.  I'm going to drill a bunch of holes in the oil tank side for cooling purposes.  I'll polish the covers so they're nice and shiny.

I modified the steel rear fender to basically replace the plastic section of the fender (splash guard or whatever it's called).  I narrowed the fender a little bit and cut off all the spot welded tabs, but left the tapped mounting tabs in place.  I blasted it clean and welded up all the holes in it yesterday, which was extremely difficult do to the paper thin steel.  Lot's of grinding still to do.  I probably should have bought a new after market fender, but I thought using the original steel fender would be cool.  It's going to get rotated around the wheel to go inside the frame.  I'll make some mount brackets for it.  I need to get the rear wheel together and swing arm back on the frame so I can get the fender placement right.  Once the fender is in place I can fab an oil tank, a battery tray and an electrical panel.  I'm thinking about using a small lithium ion battery to save space.  It's going to get tight in there.

Also the steel tubing I ordered for the rear section hoop came in yesterday.  I've got plenty to do.

[SOHC4 Cafe Racer Fan]

Moving right along. You should probably plastidip or powdercoat the fender to prevent rust.

[budman]

Today I got the bushings removed from the swing arm. I used the drop in modified flat side washer trick that I read about on this forum. I actually used three washers because the ones I had that were the right diameter were kind of thin. Just grind the sides a little until the washer will slide sideways through the bushing. I had the perfect size steel tubing to use as a driver that fit through the bushings. A few good whacks with a small sledge and out pops the bushings.  Worked great.

I couldn't get the shock bushings out, just the centers. I don't have a socket that was the right size to push out the outer ring. Guess I'll have to bust out the hack saw tomorrow, split the outer rings and drive them out.

I also got the bearings removed from the rear hub. I sprung for a special tool I bought off eBay that removes both retainers from the hub and the sprocket carrier.  You just flip the tool over and use the side you need that matches the retainer.  I used the 3/4" x 6" split bolt method that I found a link to on this forum as well.  The instructions were for a goldwing but it worked the same for the CB.  Got the hub degreased and ready to blast on Monday.

I also bought a used rear rim off EBay. Looks to be in decent shape. One step closer.