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Author Topic: '81 CB750KZ Brat  (Read 4972 times)

Offline Kezert

  • Posts: 9
'81 CB750KZ Brat
« on: Oct 06, 2015, 14:54:36 »
Hello folks,

I'm new on DTT, my name is Max and I live in Holland. This is my second bike. Before this project I owned a Kawasaki VN750 which I restored partially.

Lets get started!

About a year ago I fell in love with the looks of this bike:


So I figured I just had to have one, in that style, myself. A 1981 model CB750KZ DOHC was bought.
Bike runs good and has quite low mileage so little work has to be done on the engine side of the project.


Also bought a 1982 DOHC CB750F2 as for spare parts for a (really) small price:


I have made quite a bit of progress already, so I will be posting some updates every now and then.


Offline Kezert

  • Posts: 9
Re: '81 CB750KZ Brat
« Reply #1 on: Nov 26, 2015, 17:35:44 »
Started with tearing the 'donor' bike down. This bike is in really bad shape,
I bought it for a small price so it will just be for occasional spare parts like nuts and bolts if I need them.


Been thinking about where to put stuff like the battery and other electric components.
So I then started with tearing the project bike down. (Unfortunately I don't have many pictures of that)


Until I was left with an engine, two wheels and a frame (almost).
Lowered the forks a bit (I thought it was around 4cm) using this guide:
http://www.xs650chopper.com/2009/06/mulligan-machine-lower-your-xs650-forks-low-buck-garage-tech/

Heightened the back (about 5cm I think) with some homemade shock risers.
I used the bottom of the CB750F2 shocks (which were already ready for demolition), welded a piece of metal onto it and drilled a hole in it.

Bought a raw aluminium 19 inch fender without bracket so I started making a front fender bracket out of this old front fender from the CB750F2.


I cut it apart and took out the internal metal bracket. Formed it into shape using a vise and a hammer.


Then started grinding/cutting/welding the frame. All the unnecessary tabs were grinded off.
Then started welding on the loop and welding in some reinforcement brackets. Drilled some holes in the brackets for seat and rear fender mount.
Also welded a battery tray for the small Lithium battery to fit under the tank.
And got a leather seat made by a local lad. Ended up like this:


Picture of seat:






Offline generalyen

  • Posts: 78
Re: '81 CB750KZ Brat
« Reply #2 on: Nov 27, 2015, 16:49:39 »
Use that f tank, then you won't have badge brackets to deal with. I'd also use the f swing arm, wheel, and caliper to give you disc rear. It makes no sense not to, also use the f forks. In fact use all the f suspension. It's way better than the k suspension.  Although I just noticed that swingarm on the f is pretty rusted. But those are cheap on ebay.
« Last Edit: Nov 27, 2015, 16:52:08 by generalyen »

Offline Kezert

  • Posts: 9
Re: '81 CB750KZ Brat
« Reply #3 on: Dec 14, 2015, 15:24:06 »
Use that f tank, then you won't have badge brackets to deal with. I'd also use the f swing arm, wheel, and caliper to give you disc rear. It makes no sense not to, also use the f forks. In fact use all the f suspension. It's way better than the k suspension.  Although I just noticed that swingarm on the f is pretty rusted. But those are cheap on ebay.
Thnx for the tips Generalyen. Sadly I'm too far into the project to change things now.

Made a mount under the swingarm for the regulator/rectifier.
Just a tab of metal with holes and thread in them.



Bought a Supertrapp exhaust. I'm using the 4 into 1 exhaust system from the CB750F2.
Need to make some sort of bracket for it. Because the muffler sizes don't match unfortunately.



Some things sent to powdercoater.



And some things sand blasted.





Did a top end revision on the engine. Some pics:



« Last Edit: Dec 16, 2015, 12:25:47 by Kezert »

Offline Kezert

  • Posts: 9
Re: '81 CB750KZ Brat
« Reply #4 on: Dec 14, 2015, 15:47:26 »
Got some brackets cut for the bike.



Painted the engine with engine paint.



Got some parts back from the powdercoater. Felt like christmas eve.



Battery tray picture.



Putted some tires on the wheels (BT45). Also fitted new bearings.





Putted new bearings (front and back) in the rear fork.



Time for a little mockup. Fitted new steering bearings, assembled the front fork with new seals and oil.
Engine covers are from the F2 as I don't want to scratch the new ones just yet. Saddle and tank just mounted loose for the picture.




« Last Edit: Dec 14, 2015, 16:00:26 by Kezert »

Offline xb33bsa

  • Posts: 7726
Re: '81 CB750KZ Brat
« Reply #5 on: Dec 14, 2015, 22:56:02 »
looks hot but you are going to have some seriouis chain slack issues .you cant just adjust the chain like normal,nope, having the swingarm dropped you have to leave  a ton of slack in the chain

Offline SilkySmooth750

  • Posts: 173
  • What does "Personal Text" mean?
    • 1979 CB750 "Silky"
Re: '81 CB750KZ Brat
« Reply #6 on: Dec 15, 2015, 15:43:30 »
Looks great man!  I'm following this one for sure!

Offline armourbl

  • Posts: 68
Re: '81 CB750KZ Brat
« Reply #7 on: Dec 15, 2015, 16:51:32 »
Nice work. You seem to be moving quick. Have you done one of these before?

ben

Offline Kezert

  • Posts: 9
Re: '81 CB750KZ Brat
« Reply #8 on: Dec 16, 2015, 12:21:17 »
looks hot but you are going to have some seriouis chain slack issues .you cant just adjust the chain like normal,nope, having the swingarm dropped you have to leave  a ton of slack in the chain

Thnx xb33bsa. I don't really understand what you mean though, but I have bought new sprockets + chain so I don't think it will give me a problem. I will just have to cut the chain to the right length I think.

Nice work. You seem to be moving quick. Have you done one of these before?

ben

Thank you. This is work from the last couple of months, I already did a lot of work but haven't finished the bike yet. And no, this is the first bike I'm making into a caferacer. Just did a ton of research on the webs haha.

Looks great man!  I'm following this one for sure!

Thnx man!
« Last Edit: Dec 16, 2015, 12:24:31 by Kezert »

Offline Tune-A-Fishİ

  • DTT SUPPORTER
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  • Posts: 6844
  • BOTM LOSER Proudly Deplorable
Re: '81 CB750KZ Brat
« Reply #9 on: Dec 16, 2015, 16:02:13 »
Badass way to make that tank work!! the line at the bottom turns it into a completely different tank.... Gohddang!



XB's right on duh chain mang... the counter sprocket is static and the swinger goes up and down yes??

Look here: and see if you might be too lowrider on the swinger.
"I didn't come here and I ain't leavin"  Willie Nelson

"love hard, live fast, die fun" Kacey Musgraves

"Like a Wreckin Ball!" Eric Church