1981 CB750K Project Superleggera

More minor progress.

Headlight mounts came in. I was having real trouble finding some 51mm fork mounts that I liked online. Then inspiration struck me, I changed my search to 2" roll bar mounts and my options increased a thousand fold. So I ordered these simple little beauties:


And after a bit of a struggle I got both sets on.


I've also realized that I have some wiring logic wrong somewhere. My rear running light is only on when the high beam is on. So I've gotta get that sorted out at some point.

Finally had the motivation to get the headlights aimed. Took a few pics to show the ridiculousness that is 13,200 lumens of output. I feel like the phone actually did a really good job of recreating what I was actually seeing, which is rare with phone cameras in my experience.

For comparison, the street without any lighting:


Low beam (the flood):


And high beam (the spot):


Very happy with the performance of the lights, now we just have to see how they hold up to the abuse. Or if they're annoying enough to get me pulled over.

Damn, those are some strong lights Nice

Wow!! Those are brighter than I thought they could be!


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More tiny progress. With the 17" front wheel the side stand was useless effectively. So I found a nice local shop that does custom fab work (which will come in handy later) and had them shorten the side stand about an inch.



You can barely even tell it's been touched, which is exactly why I outsource welding. The bike actually leans to the left on the stand, instead of to the right. Much more convenient than using the center stand constantly.

So the new forks lowered it so you had to shorten the side stand?


82 Honda CB900C is my first attempt of a bike upgrade

The forks were actually the same length uncompressed, it's the change to the 17" wheel from the stock 19" that changed the geometry the most.

Very minor update:

Parts fairy visited while I was relaxing on the beach


CBR1100XX rear suspension minus the shock. I'm still leaning towards dual shock but my fabricator wants me to go single. So now's the time to start sorting that out. But before that I'll need to start taking measurements and see what I need to slap this thing in frame.

More parts in! After over a month of waiting and several unanswered emails my Acewell speedometer arrived. Wiring that up is going to be a fun time I'm sure.


Today my Bonamici Racing rearsets arrived. I went with 04-05 ZX10R rearsets because they seemed to mount in a fashion that would make fabbing them to the frame the easiest. The shift linkage also will require minimum work to get working (hopefully).


Finally decided to start everyone's favorite bit, the tear down.






It's been fairly hot and I haven't been very motivated to find friends to help with the engine removal but it'll come soon. My CBR1100XX swing arm is with my fab guy getting all the crap I don't want cut off. Once the frame is stripped it's going in for the same treatment and then we'll be sorting out mating the swingarm to the frame and putting things back on.

This part really is a pain.

Coming along nicely, that was a hard part but it's done. Heavy isn't it?

Unbelievably heavy. Not looking forward to putting it back in lol.

While I'm waiting on my custom swing arm bushings to be finished, I decided to start with one of my little side projects. I'm going to try and implement what I'm calling the poor mans quickshifter. The prebuilt kits I've found go for $300, mine costs about $20 so far, and will be easily adaptable to different bikes.

Utilizing a microswitch on the rearset and a couple of relays I plan to interrupt the ignition during upshifts when the clutch is not pulled in. The current design requires the use of a GP shift pattern, but I planned to run that anyway. This will (hopefully) allow for rapid shifting when I want without any interruption of smooth operation at lower speeds. To mount the switch I modeled my left rearset, put it in an assembly, and used that to draw up a first iteration for the switch mount.





I plan on 3D printing the mount, but if fiber reinforced nylon proves too fragile I may shift to a carbon construction. Ideally the mount won't see any load higher than the force required to throw the switch, but the ideal and reality rarely coincide in my experience, so we'll see.

It's not so bad, just put the frame on around the motor. Then put you front and rear suspension on. It makes life a lot easier.

Carbon fiber reinforced nylon plastic, print time: 38 minutes. What a magical time we live in boys.







My switch and relays should be here monday. Not that I have a bike to test them on yet.

As an ME student I have to say it is fascinating seeing the blending of old school steel and modern rapid mfg tech on this build. Keep up the great work. I know you've inspired me.

That's the goal man!



Super minor update, got the switches and relays half wired up. Still need to buy my harness connectors but I'm in limbo waiting on my custom bushings for the swingarm. Hopefully they'll be done early next week.

My goal is for the bike to be done in time for the distinguished gentleman's ride, we'll see how that goes.

Well It's been a while but I've finally started making progress again. I outsourced some welding to a shop that took their sweet time and then we got hit by a hurricane but I've finally got my frame back and she's coming along again.

The shop also cut down my new swingarm and made some new inserts so I could keep the original bolt and not have to bore out the holes in the frame.

I decided not to go mono-shock, I love the aesthetic of the dual shocks so the first project was fabbing some mounts for them. I started with a very simple model based on measurements from the old swingarm and some 0.625" thick 6061-T6 aluminum bar stock.


I began by center-punching the holes, started them with a #5 center drill, then ran a 3/8ths bit before finishing with the final 3/4 bit. Then I cut the stock on the drop saw and finished it with the band saw and belt sander. I didn't take any pics of this part because the band saw and belt sander are both terrible and I was focusing on not losing any fingers ;D

Once that was done I did a quick mock up and in exchange for a case of beer my buddy went to town with the tig.




Once they were on and the swingarm cooled off a bit I started the next step, bushing inserts for the shocks. I was originally planning on running OE bushings but unsurprisingly the part is discontinued. One of the perks of a 35 year old bike. Thankfully we had some delrin round stock laying around so I finally got around to learning how to run our lathe and made my own.


Took a couple tries to get right, the first two attempts both wound up around 0.743" and since I need to press fit them in a 0.75" hole that wasn't gonna work. I was getting quite a bit of runout on those tries, 3 thou across less than 2" on the OD so I parted off one bad run and changed the tool insert to a less beat up one and managed to get them down to 0.755" on the last attempt with only about 5 tenths of runout, which is good because I was out of stock by then.

I was a bit worried about the welding distorting my mounts, but they stayed round and the inserts went in with a little hammering and not much fuss.



With that out of the way I had one last project to get done for the rear suspension install. The swingarm is from a 1997 Honda CBR1100XX Blackbird, which I learned (after buying the setup) has linked brakes. 3 Master cylinders and 10 different brake lines allow the front brake lever to operate the rear brake and vice versa. This is done by splitting the calipers into two sections. The outboard pistons of each brake are operated by the usual brake master cylinder. The center piston is operated by the other master, so the front brake lever actuates the rear brake center piston. I'm definitely not going to link the brakes on the CB, so I looked for a solution and found that the center brake piston is shallower than the outer two, and you can connect the center piston to the outer pistons by drilling down into the galley. So we went back to the drill press.

These bolts were a pain to get out, red loctite and everything, it's like they don't want the brakes to come apart or something.


Pulled apart and locked on the press, ready to go.


Again I drilled a pilot hole and then stepped up to a half inch bit since I didn't know how big the passage behind the cylinder was. I may have forgotten to tighten the chuck on the pilot hole.


But the bit was fine so I kept going, hit the passage, and then spent about 10 minutes blowing compressed air into every orifice to clear out the chips before putting her back together.


After that was done I took the parts home and mocked up the new setup. The last bit of welding I have to do with the rear hoop, but I wanted to have the swingarm on first to verify my clearance before I bend the tube and slap it on. For fun I tossed on my new rearsets to check the positioning. Unfortunately I haven't grabbed nuts for them yet so they just kind of fell off, but they looked decently placed before that 8)


Today I'm hunting down the rearset hardware and hopefully I'll have the rear hoop on next week (if we have any tubing laying around that has the correct OD) and I can start pawning everything I own to pay for an m-unit, m-button, and a bunch of connectors to rebuild the harness.

I am in for this! Very exciting! Supreme work thus far, bbq

Supercool and great work envious of this build love the modern add on's ime in to the finish keep up the good work bud