omgwtfbbq!
Active Member
Cookie said:
yorkie350 said:
Thanks guys! I hope to get her running again by the end of the year, then start in on the cosmetic mods (carbon and all that).
1981 CB750K Project Superleggera
- Thread starter omgwtfbbq!
- Start date
Thanks guys! I hope to get her running again by the end of the year, then start in on the cosmetic mods (carbon and all that).
omgwtfbbq!
Active Member
Snapped a quick pic of the clearance test. Definitely recommend you engage your safety squints when doing this with harbor freight ratchet straps.
Good news is the wheel cleared everything just fine. Don't know what setups guys are running where clearance is a problem, I could run a straight hoop and not hit the tire.
Good news is the wheel cleared everything just fine. Don't know what setups guys are running where clearance is a problem, I could run a straight hoop and not hit the tire.
coyote13
Over 1,000 Posts
Most guys (who don't know better) run a hoop straight off the line of the seat frame rail and end it right over the top of the tire. If you draw that straight line in your picture it would be touching not just the tire but the RIM. Yours looks like it would clear with a hoop because your rear frame rails kick up instead of continuing on a straight line.
omgwtfbbq!
Active Member
coyote13 said:
Right, I forgot the older bikes don't have the kickup in the frame that the DOHC bikes have. That makes a lot of sense.
Nice bike, I like the modern vision of a light caferacer. Mine has a USD fork as well 
omgwtfbbq!
Active Member
Little more progress today, cut the excess bits off my upper triple and drilled/tapped the hole to mount my new gauges.
At the start with some of the implements of destruction. I plan on running RFID ignition so I don't need all the bits for the OE ignition cylinder anymore. Yay weight reduction.
Big chunks cut off with the cutoff disc, now onto the grinding wheel for the meat of whats left.
Got a bit tired of grinding and decided to drill and tap the hole for the gauge mount. Finally found a 17/64s bit and tapped it M8x1.25.
And then got back to smoothing things out with the air sander. 50 grit to get the last the grinder left, and a scotch brite pad to smooth everything off.
The only thing left now was to toss it on the bike and see how it looked. I'm very happy with the placement of the gauges and now all I need for this is some more appropriate hardware.
The last major piece I'm missing now is the hoop. Does anyone make premade hoops for the DOHCs? I can't seem to find one that is the right size (7.75" diameter) and my pipe bender only goes down to 9". Once I get a hoop welded on she'll be going back together finally.
At the start with some of the implements of destruction. I plan on running RFID ignition so I don't need all the bits for the OE ignition cylinder anymore. Yay weight reduction.
Big chunks cut off with the cutoff disc, now onto the grinding wheel for the meat of whats left.
Got a bit tired of grinding and decided to drill and tap the hole for the gauge mount. Finally found a 17/64s bit and tapped it M8x1.25.
And then got back to smoothing things out with the air sander. 50 grit to get the last the grinder left, and a scotch brite pad to smooth everything off.
The only thing left now was to toss it on the bike and see how it looked. I'm very happy with the placement of the gauges and now all I need for this is some more appropriate hardware.
The last major piece I'm missing now is the hoop. Does anyone make premade hoops for the DOHCs? I can't seem to find one that is the right size (7.75" diameter) and my pipe bender only goes down to 9". Once I get a hoop welded on she'll be going back together finally.
omgwtfbbq!
Active Member
Little more progress. Finally got a rear hoop, cut it down, welded it on, refinished the frame and painted the swingarm to match. Today the goal is reassembly!
Test fit after cutting the hoop down
Staring deep into the pretty blue light
Didn't blow any holes in it!
After the final round of paint
Test fit after cutting the hoop down
Staring deep into the pretty blue light
Didn't blow any holes in it!
After the final round of paint
CarbsAndCylinders
Careful With That Axe Eugene
I usually prefer aluminium swing arms polished up but this one looks great all black and glossy.
omgwtfbbq!
Active Member
CrabsAndCylinders said:
Yeah I like the polished look usually, but after putting it together I'm glad I went with black too.
omgwtfbbq!
Active Member
A few more minor updates while I await delivery of my new rear sprocket:
Finished my wiring diagram!
What an enormous pain that was, but hopefully it'll save some headache later. I've finally ordered all the connectors I need to build a new harness so the bike might actually run again soon.
On my breaks from doing wiring diagrams I stripped and sprayed my tank:
The tank is temporary, but I figured I'd mess with it anyway because I'm not looking forward to the work I'm probably gonna have to do to get a chain on this thing.
Finished my wiring diagram!
What an enormous pain that was, but hopefully it'll save some headache later. I've finally ordered all the connectors I need to build a new harness so the bike might actually run again soon.
On my breaks from doing wiring diagrams I stripped and sprayed my tank:
The tank is temporary, but I figured I'd mess with it anyway because I'm not looking forward to the work I'm probably gonna have to do to get a chain on this thing.
How do you like that TDi Cup?
omgwtfbbq!
Active Member
Love it. Especially now that it has decent tires and not the all-seasons it came with from the dealership.
omgwtfbbq!
Active Member
Rear sprocket came in!
This thing is a featherweight. Full 7075-T6 47 tooth 520 sprocket, not the fanciest one they sell but with the high wear rate I'm not willing to spend $80+ every time I need a new one.
Dreading the work ahead I decided to buy a front sprocket on the assumption I'd need to machine it anyway. My local race shop had one in stock for an '04-'12 CBR1000RR.
If you're unaware, every Honda (post 79 at least) uses the same output shaft spline, so it's trivial to mount any sprocket. I needed about a 530-sprocket width offset to get the front in line with the new rear, and since I was able to find no offset sprockets for the DOHC CB750 I had resigned myself to having to fabricate something.
Welllllllll I popped the CBR sprocket out and noticed that it was offset rather far to the inner side. But since sprockets are round they work the same backwards, so I flipped it around and popped my chain on to see how much more I needed to push it out.
Bam! Super super happy with the fitment, super glad I don't have to turn the teeth off the stock sprocket to make it into a spacer. 8)
With that sorted I broke the chain to length and almost made an expensive mistake when I broke it a link shorter than intended.
Luckily it still falls within the adjustment range of the swingarm and I don't have to run two master links like a buddy of mine who bought a bigger rear sprocket and broke his new chain to match the old length ;D
So now all that's left is to get my carbs back from my buddy who needed a set to get her bike running for an event a couple months back, then a quick harness build once my connectors come in.
Friday I plan on laying up a carbon fiber electric tray/fender for the rear to hold everything that will be hiding under the seat so look for pics of that process this weekend!
This thing is a featherweight. Full 7075-T6 47 tooth 520 sprocket, not the fanciest one they sell but with the high wear rate I'm not willing to spend $80+ every time I need a new one.
Dreading the work ahead I decided to buy a front sprocket on the assumption I'd need to machine it anyway. My local race shop had one in stock for an '04-'12 CBR1000RR.
If you're unaware, every Honda (post 79 at least) uses the same output shaft spline, so it's trivial to mount any sprocket. I needed about a 530-sprocket width offset to get the front in line with the new rear, and since I was able to find no offset sprockets for the DOHC CB750 I had resigned myself to having to fabricate something.
Welllllllll I popped the CBR sprocket out and noticed that it was offset rather far to the inner side. But since sprockets are round they work the same backwards, so I flipped it around and popped my chain on to see how much more I needed to push it out.
Bam! Super super happy with the fitment, super glad I don't have to turn the teeth off the stock sprocket to make it into a spacer. 8)
With that sorted I broke the chain to length and almost made an expensive mistake when I broke it a link shorter than intended.
Luckily it still falls within the adjustment range of the swingarm and I don't have to run two master links like a buddy of mine who bought a bigger rear sprocket and broke his new chain to match the old length ;D
So now all that's left is to get my carbs back from my buddy who needed a set to get her bike running for an event a couple months back, then a quick harness build once my connectors come in.
Friday I plan on laying up a carbon fiber electric tray/fender for the rear to hold everything that will be hiding under the seat so look for pics of that process this weekend!
omgwtfbbq!
Active Member
Thanks guys!
Been making more progress this week. High on the list of getting the bike running again is new mounts for all the electrical goodies. Since super light is the name of the game here the obvious solution was carbon panels. While making the panels I figured I might as well use some of my carbon scraps for a little bit of aesthetic enhancement as well.
The process:
Start with your carbon fabric of choice. I could have gone with some fancy stuff here but the tray will be basically invisible so I stuck with basic 2x2 cloth. The tape on the edges is for fray control.
I laid out the fabric on an aluminum plate to make sure the two panels would both fit. The larger will go under the tail and hold the M-unit and CDI units, the smaller just behind the fuel tank to hold the reg/rec.
After wetting out each layer of fabric we add a release film and a bleeder cloth to absorb the extra resin then bag it up and pull a vacuum to check the seal. You can see the small secondary plate that's got the scraps on it. Both of these were sealed perfectly the first time around, which is a first for me.
Then into the oven to reduce the cure time from 24 hours to 4 hours
A few hours later the part are ready to come off the plates. You'll note the rough surface finish on the top side, this is caused by the bleeder fabric unevenly distributing the pressure from the bag and is the downside to this style of carbon fiber manufacturing. But again, these parts will largely be hidden so surface finish is not an issue.
At this point I started knocking out the aesthetic bits since I didn't have the proper measurements for the trays. My bike has bonamici racing rearsets for a ZX10R and they come with metal heel guards. I decided to make some slightly better looking versions of them. So to start I roughed out the shape on a band saw with a backwards blade.
Finer detailing was done with a hand held router, and final shaping was done with a palm sander. Only thing missing now is mount holes.
At this point the stock guards were 20gr and my copies were 6gr. But the carbon was quite a bit more flexible that the aluminum, so to fix that and make them look a bit more pretty I did a hot coat, or a second application of resin on cured carbon. This has the effect of stiffening the part (at the cost of weight) and giving the carbon that deep shine everyone loves.
After a night curing normally and a morning in the oven at low heat the hot coat is cured and the parts are ready to be drilled and mounted.
At that point I got distracted by the fact that I finally had my carbs back so I put them back on. The only thing left to get the bike running again is the harness and electrical mounts. Kitty wants to know why it's taken so long.
This week hopefully I'll be able to finish those trays, get a battery mount sorted out, and build the harness so I can take her out and piss off all my neighbors with my lack of exhaust!
Been making more progress this week. High on the list of getting the bike running again is new mounts for all the electrical goodies. Since super light is the name of the game here the obvious solution was carbon panels. While making the panels I figured I might as well use some of my carbon scraps for a little bit of aesthetic enhancement as well.
The process:
Start with your carbon fabric of choice. I could have gone with some fancy stuff here but the tray will be basically invisible so I stuck with basic 2x2 cloth. The tape on the edges is for fray control.
I laid out the fabric on an aluminum plate to make sure the two panels would both fit. The larger will go under the tail and hold the M-unit and CDI units, the smaller just behind the fuel tank to hold the reg/rec.
After wetting out each layer of fabric we add a release film and a bleeder cloth to absorb the extra resin then bag it up and pull a vacuum to check the seal. You can see the small secondary plate that's got the scraps on it. Both of these were sealed perfectly the first time around, which is a first for me.
Then into the oven to reduce the cure time from 24 hours to 4 hours
A few hours later the part are ready to come off the plates. You'll note the rough surface finish on the top side, this is caused by the bleeder fabric unevenly distributing the pressure from the bag and is the downside to this style of carbon fiber manufacturing. But again, these parts will largely be hidden so surface finish is not an issue.
At this point I started knocking out the aesthetic bits since I didn't have the proper measurements for the trays. My bike has bonamici racing rearsets for a ZX10R and they come with metal heel guards. I decided to make some slightly better looking versions of them. So to start I roughed out the shape on a band saw with a backwards blade.
Finer detailing was done with a hand held router, and final shaping was done with a palm sander. Only thing missing now is mount holes.
At this point the stock guards were 20gr and my copies were 6gr. But the carbon was quite a bit more flexible that the aluminum, so to fix that and make them look a bit more pretty I did a hot coat, or a second application of resin on cured carbon. This has the effect of stiffening the part (at the cost of weight) and giving the carbon that deep shine everyone loves.
After a night curing normally and a morning in the oven at low heat the hot coat is cured and the parts are ready to be drilled and mounted.
At that point I got distracted by the fact that I finally had my carbs back so I put them back on. The only thing left to get the bike running again is the harness and electrical mounts. Kitty wants to know why it's taken so long.
This week hopefully I'll be able to finish those trays, get a battery mount sorted out, and build the harness so I can take her out and piss off all my neighbors with my lack of exhaust!
omgwtfbbq!
Active Member
More progress! She lives! More on that in a bit.
Last week my brake light came in, this thing is nice. I've seen a few builds with cheap chinese LEDs and they just do not compare to the real deal. This thing is slim and bright.
With a little bit of heat I managed to get it formed to the rear hoop. And it's almost actually centered.
Next up I finally went out and got a battery. I ended up spending a bit more than I wanted to, but this thing fits so well and weighs so little I think it was worth it. (zip ties are not the permanent mounting solution)
With the battery and M-unit roughly located it was time to start building the new harness. I decided to go mil-spec (aka lazy) and just bought a single spool of white wire. Will this make troubleshooting a giant pain for future me? Probably. But that is future me's problem.
The best thing about the m-unit is you can just cut down the wires at the unit side to take up slack in the harness.
After I finished the first go at the harness I tossed the bike back together and tried to fire it up. It would stumble but not run. I verified the timing and all the carb adjustments and she would just not fire. Then I realized that I was an idiot and the 18awg wiring I used was probably too small for the ignition system to properly fire the coils. So I re-did that bit of the harness with some 14awg and I now have what is probably the loudest bike in the state.
The carbs need to be adjusted a bit so she backfires now and then and when it does it legitimately sounds like gun fire. I went for a short ride to get gas and see how she rode at speed with my buddy who rides a Harley (usually with other straight piped harleys) and he had to speed off ahead because he couldn't take the noise riding behind me ;D
It was great to be out riding again but the project is far from done. Next on my list are the carbon tail trays to securely mount the electronics and tag, a yoshi style exhaust from carpys so my neighbors don't burn my house down, the bar end blinkers from moto-gadget (and mirrors that work with them), and hopefully early next week she'll see the scales again so I can see how much weight she's lost on her diet.
Last week my brake light came in, this thing is nice. I've seen a few builds with cheap chinese LEDs and they just do not compare to the real deal. This thing is slim and bright.
With a little bit of heat I managed to get it formed to the rear hoop. And it's almost actually centered.
Next up I finally went out and got a battery. I ended up spending a bit more than I wanted to, but this thing fits so well and weighs so little I think it was worth it. (zip ties are not the permanent mounting solution)
With the battery and M-unit roughly located it was time to start building the new harness. I decided to go mil-spec (aka lazy) and just bought a single spool of white wire. Will this make troubleshooting a giant pain for future me? Probably. But that is future me's problem.
The best thing about the m-unit is you can just cut down the wires at the unit side to take up slack in the harness.
After I finished the first go at the harness I tossed the bike back together and tried to fire it up. It would stumble but not run. I verified the timing and all the carb adjustments and she would just not fire. Then I realized that I was an idiot and the 18awg wiring I used was probably too small for the ignition system to properly fire the coils. So I re-did that bit of the harness with some 14awg and I now have what is probably the loudest bike in the state.
The carbs need to be adjusted a bit so she backfires now and then and when it does it legitimately sounds like gun fire. I went for a short ride to get gas and see how she rode at speed with my buddy who rides a Harley (usually with other straight piped harleys) and he had to speed off ahead because he couldn't take the noise riding behind me ;D
It was great to be out riding again but the project is far from done. Next on my list are the carbon tail trays to securely mount the electronics and tag, a yoshi style exhaust from carpys so my neighbors don't burn my house down, the bar end blinkers from moto-gadget (and mirrors that work with them), and hopefully early next week she'll see the scales again so I can see how much weight she's lost on her diet.
djmaynard
Been Around the Block
I had yoshi exhaust from Carpy’s also. Came in last week, but haven't gotten a chance to install. Again, you're doing great! Where did you get the tail light from?
Sent from my iPhone using DO THE TON
Sent from my iPhone using DO THE TON
Cookie
God help the child who grows out of everything
Man that's an awesome build. Glad to hear it's up and running (and a touch jealous you can go on a test ride in January)!
If I may offer a suggestion, I'd further upgrade the size of your supply wires to your coils and add a relay. Look up "cb750 ignition coil mod" on here or on Google, another good side for it is cb750c.con and has simple schematics. I did the mod using 10awg wires and my cold start and idle characteristics are vastly improved.
The OEM wiring powers the coils through a a skinny (maybe 16awg?) wire from the kill switch. Use this wire to flip a relay and run direct battery power through the relay to the coils with the heavy gauge wire.less voltage drop and more consistent supply are the result.
If I may offer a suggestion, I'd further upgrade the size of your supply wires to your coils and add a relay. Look up "cb750 ignition coil mod" on here or on Google, another good side for it is cb750c.con and has simple schematics. I did the mod using 10awg wires and my cold start and idle characteristics are vastly improved.
The OEM wiring powers the coils through a a skinny (maybe 16awg?) wire from the kill switch. Use this wire to flip a relay and run direct battery power through the relay to the coils with the heavy gauge wire.less voltage drop and more consistent supply are the result.
omgwtfbbq!
Active Member
djmaynard said:
When you do get it on can you do me a favor and measure the clearance between the exhaust and the swingarm? The CBR swinger is quite a bit wider and I'm currently planning on buying the mild exhaust so I can bend it out a bit, but if it clears by enough I'll just get the ceramic coated one and not worry about it.
The taillight is from Revival Cycles, you can find it here: https://revivalcycles.com/products/flexible-led-taillight
I got the 8.2" one with amber turn signals and it is perfectly sized and very bright.
Cookie said:
Well the weather turned cold today so apparently the motorcycles gods weren't happy with me being out and about lol. I'll definitely look in to the wiring change, you can never go wrong with more power.
