Author Topic: cb750 racer build  (Read 5161 times)

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Offline themotoworks

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cb750 racer build
« on: April 25, 2009, 06:04:59 AM »
I've been working on a major summer project and posting on dotheton a lot, so i figured i'd share this here too... i'm building a 74 cb750, with alloy tank, seat and fiberglass race fairing which will have a vac molded plexi windscreen.  this has been a real learning experience for me, as I usually do the body work in fiberglass only.  I'm liking the aluminum though as one off parts don't seem to take as long to do... I'm mocking up the parts on another 750 i have still assembled, then moving them over to the new frame.   


getting close to a finished swingarm, got the axle blocks back today from my machinist friend and they are KILLER!!! so I welded those up, forgot to tap one before I welded it and went DUH so now I'll have to come up with some kind of 6" tap extension before I can ride... got a 77lb piece of 1/2" plate steel for my jig too, seems to work really well, good and flat and great for clamping.  machined up my pivot tube too, it's got needle roller bearings and needle thrust bearings, and the swingarm is still 4lbs less than stock, should help the back end really stick to the ground!





tacking up the pivot tube to make sure everything clears before final alignment and welding, there's going to be a crosstube in there too, 2X1" al tube





Almost done with the body too!








almost done, just gotta weld on the shock mounts, and a tab for the brake bar and we'll be golden... I think had I had it all to do over again, I may have just powdercoated the old stock one....... I guess we'll see how much of a performance difference I get



all assembled, I'm actually going to do a more square alloy seat for it, the tank came out looking less round than I imagined, so now the seat doesn't quite match
« Last Edit: April 25, 2009, 06:11:55 AM by roccitycafe »
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Offline SOHC4 Cafe Racer Fan

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Re: cb750 racer build
« Reply #1 on: April 25, 2009, 07:18:24 AM »
Hey Sean,

Great looking swing arm.  I think your aluminum Dunstall seat looks amazing.  Fantastic finished look!
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Offline FunJimmy

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Re: cb750 racer build
« Reply #2 on: April 25, 2009, 10:35:22 AM »
It's a thing of beauty!

Keep us posted.

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Offline ev0lve

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Re: cb750 racer build
« Reply #3 on: April 25, 2009, 11:11:40 AM »
Jaysus! This will be a righteous build. Subscribed!

Offline themotoworks

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Re: cb750 racer build
« Reply #4 on: April 29, 2009, 11:41:37 AM »
got the engine in!  starting to look like a bike now, and I love how there are so few extra things on this bike.  very minimal and light!

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Offline cdoggy81

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Re: cb750 racer build
« Reply #5 on: April 29, 2009, 08:51:00 PM »
very cool!

Offline 754

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Re: cb750 racer build
« Reply #6 on: April 29, 2009, 09:23:14 PM »
Looks good,
 Hope you are running a hardened shaft or collars on them needle bearings, and  that you are heat treating that swingarm..
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Offline themotoworks

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Re: cb750 racer build
« Reply #7 on: April 30, 2009, 04:30:52 AM »
the heat treater actually recommended a stress relief, I don't know if that restores temper, but I'll leave it in the hands of the pros
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Offline papp101

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Re: cb750 racer build
« Reply #8 on: April 30, 2009, 08:31:15 AM »
Excellent build, can you give some more details about your process on making the Front Fairing?

Offline themotoworks

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Re: cb750 racer build
« Reply #9 on: April 30, 2009, 04:09:00 PM »
Looks good,
 Hope you are running a hardened shaft or collars on them needle bearings, and  that you are heat treating that swingarm..

thinking more about this, the shaft is hardened, but there's no collar around the bearing unit, it's self contained and sealed, but do you think I should machine a bronze sleeve for it to distribute the load over a wider area?
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Offline burmashave

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Re: cb750 racer build
« Reply #10 on: April 30, 2009, 07:00:58 PM »
Very impressive build! I'm looking forward to progress as well.
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Offline kghost

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Re: cb750 racer build
« Reply #11 on: April 30, 2009, 07:03:08 PM »
Shame you bondo'd that tank....Aluminium looks so nice polished.

Dig your swing arm....May do one like that on my build.

Looking good.
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Offline themotoworks

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Re: cb750 racer build
« Reply #12 on: May 01, 2009, 12:29:07 PM »
yeah, it's one of my first tanks, so it wasn't perfect enough to polish and i meant for the whole bike to be done in honda red anyway
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Offline 754

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Re: cb750 racer build
« Reply #13 on: May 01, 2009, 08:19:58 PM »
What I was getting at on the needle bearings was, if they are not shaft size, then you either open up the holes in frame, or build sleeves to take up the difference.. but that would be tricky as they would be VERY thin.

Bronze aint the anwer, the bearings have to run on a hardened surface.. to the best of my knowledge
Maker of the WELDLESS 750 Frame Kit
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My next bike will be a ..ANFOB.....

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Lost quite a few CB 750's along the way

Offline themotoworks

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Re: cb750 racer build
« Reply #14 on: May 02, 2009, 05:33:32 AM »
oooh gotcha, yeah, the bearings are metric, so they fit on the shaft perfect, and they're a press fit into the swingarm pivot
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Offline bill440cars

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Re: cb750 racer build
« Reply #15 on: May 02, 2009, 11:40:14 AM »

       Have to agree with the others, about the quality of this build! :) So much attention to detail AND such features (swing arm, gastank, fairing, etc)!!!!!!!!!! :o 8) ;)



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Offline themotoworks

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Re: cb750 racer build
« Reply #16 on: May 05, 2009, 07:51:39 PM »



almost finished with the exhaust... header pipes are all figgered out, just have to get the 1&2 pipes done from the headers back to the megaphones
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Offline b20z

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Re: cb750 racer build
« Reply #17 on: May 06, 2009, 01:20:55 PM »
Nice Build so far. What oil tank is that?

Offline 78CB750CAFE

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Re: cb750 racer build
« Reply #18 on: May 06, 2009, 02:16:27 PM »
wow.
lots of work you have in this so far, can't wait to see it done.
any interest in doing swingarms for others?
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Offline themotoworks

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Re: cb750 racer build
« Reply #19 on: May 06, 2009, 05:18:13 PM »
wow.
lots of work you have in this so far, can't wait to see it done.
any interest in doing swingarms for others?

actually I have to build a jig to do a rework on the swingarm... if I do that maybe I'll look into building more of them, offer them for sale this fall after I see how this one performs, not sure of the price point though, the machined parts and material costs plus labor would probably put them in the neighborhood of $6-700, think there's interest there?
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Offline moham

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Re: cb750 racer build
« Reply #20 on: May 06, 2009, 09:15:40 PM »
What's the story with the motor? Have you done any mods there? Very convincing racer look so far. Something about a custom swingarm that turns heads...
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Offline themotoworks

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Re: cb750 racer build
« Reply #21 on: May 07, 2009, 05:53:39 AM »
the motor is stock, just tuned up and checked over good.  the goal of this build was to get it done quickly, which is funny because it's been taking me a while since things have turned busy (not bad!!), i can't imagine how much longer it would take me with serious engine mods!! haha
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