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Honda CB750 Restore Cafe Racer

1K views 6 replies 5 participants last post by  Elwood 
#1 ·
I recently purchased a 1981 Honda CB750 DOHC that I'll be restoring. I know it's not a Kawi, but this forum is cool so I'll post pictures and updates as I go.

My plan:
Check Valve Clearance
Change Oil
Adjust Carbs (bench)
Balance Carbs
Flush Brake Fluid
Replace Brake Lines (with handlebar, see below)
Change Fork Oil / Seals
Tires

This should get it in running condition. Then, the plan pt II is

Lower handlebars (and throttle/clutch cables that go with it)
Tuck any loose wiring
Reposition starter button and choke
Seat / Seat Base
Cut off stupid pointy tail
Weld on flush fitting seat bar
Low profile brake/turn light w license plate bracket
Paint Tank



 
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#4 · (Edited)
Alright, this baby is on the road! Here's how I got there:

I had a thread on here about cleaning the carbs. Between that and an excellent guide I found, I got the carbs clean. It took two tries. The first time I didn't get the slow speed passage clean (you can't see it from the outside), but following the guide, specifically the part about 'spray in this hole until it comes out the specified hole'
http://zx6r.com/mechanical-technical/69951-1981-cb750-general-carb-cleanup.html
http://www.cb750c.com/publicdocs/SeanG/Honda_Carb_Manual_revG.pdf

Once carbs were clean and back on, I removed the fuel petcock I received with the bike (it was from a different model) and replaced it with a non-vacuum one. The SOS had already been removed. The one I removed was too wide and the tank would not install without the petcock hitting the valve cover or carbs.

I picked up a cheap brat seat, and cut off the old pointy tail. Now that I had the engine running where I could be confident the project would work, I started on the external elements.

I welded the tail hoop on. My second time welding and it was some work, but I got it in the end. Added a cross-brace under the seat since these bikes need stiffness at the back that cutting the tail short removes.

Every piece I took off I cleaned, so it's much shinier now than it was before.



Brake caliper rebuild, new stainless lines, radial master cylinder.

Brakes off the forks. Ordered a rebuild kit. They were pretty tight, but I got them out using an air compressor with the nozzle jammed in the brake line hole. They came off at high velocity, but I was prepared.




Got the forks off. Cleaned everything while I was at it. On the fork bodies, you can tell which one was on the right side of the bike, because it was more exposed when the bike was on the kickstand.



I got new Sonic Springs, and replaced the oil with 15wt fork oil. It seems to be great so far. I have all my replacement parts ordered and ready to go in.




Slide the fork seal 'stack' onto the fork tube, then put the fork body in place. I found the only way I could get the copper/teflon seals in was to cinch them with a zip tie so they were compacted, then tap them down into place. Once they were in their slot, I was able to nick the zip tie with a sharp knife/exacto, and remove it.

I made my own fork seal driver with a cut out bit of PVC. This is a pvc pipe straight joint that i cut a slot out of, and removed the rib in the center with an angle grinder. I used this to drive the copper/teflon seals with the metal spacer over them, then used it to drive the main fork seal with the spacer over it.





I was ordering a new chain, so I ordered a new sprocket too. The old one looked a little worn. Probably had life left, but now I have a matching set. Put a new front sprocket on as well.





Now it's back together with new tires, clean wheels, refreshed brakes, refreshed forks, etc.



I have a couple things left: I need side covers. I'm wondering if I should just cut some leather, waterproof it, and put ties through grommets on it to manually tie them in place. It'd look old school.

I already ordered a brake/light turn signal combo for the back. I need to install that. I need front turn signals. I'll probably get small ones and mount them where the OEM ones were.

The neutral light and oil light I shorted on the sprocket cover and starter cover, respectively. It took me a little while, but the folks on cb750c.com were super helpful. Fixed those issues, and took it out for a longer ride today. Mixed rain but I got a nice sunny window.



 
#5 ·
Nice work.
Depending on the engine work, I will give you a warning.
Bought mine 1979 with 4 k miles, spent a lot of money on NOS parts.
Drove it until 8 k miles and the cam chain tensioner broke.
Engine rebuild later with new ones.

The design of them isn't great, a steel sheet that is curved with rubber, it was the rubber that failed. Sitting for years it had dry riot.





OH, in hind sight. Get some Mukuni's direct slide carbs.
Those dam CV carbs are a constant PITA.
 
#7 ·
Your CB750 looks really good! I still miss my old 1972 CB750. I really got a kick out of passing people on the highway on a bike with antique tags. A big plus was the sound, it wasn't the fastest bike but the 4-1 with no baffle and pretty well tuned carbs sounded mean as all hell.

 
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