Author Topic: 73 racer build (Read 7972 times)

Jhelgesen · « **on:** August 07, 2014, 09:21:47 AM »

Hi Guys, wanted to share my project with the group, and see what the collective knowledge base thinks.

I have a 73 cb550 that was in storage for a few decades (actually had a pair of them, and took one back to stock), using this as my starting point.

I have the engine running and carbs cleaned out, electrical system in good shape.

From there, the deconstruction happened. Added the CX tank and the sport wheels I wanted. I wanted to keep the rear drum brake, so I'm using cb750A wheels. Gave me a 2.5" wide rear rim

Swapped on the cbr600rr front end.

Using my handy dandy 3d printer, sampled the spacers needed to adapt the brakes to the wheel.

Question for the group, should the axle be slightly shorter than the spacers and stack up, to put the assembly in compression when tightened?

Made the frame changes I wanted in the rear, and did some stitch welding on the front to stiffen it up. Then got her outside for some pics.

Ravie · « **Reply #1 on:** August 07, 2014, 09:30:58 AM »

Very cool. I'm trying to use that same tank on my CB750 build and I think I finally came up with a good mounting system. I just need to get a few bolts welded in place to mount the rear, and the front I need to weld in some extensions to fit the narrower mounts.

I LOVE those wheels.

Jhelgesen · « **Reply #2 on:** August 07, 2014, 09:40:02 AM »

The space under that tank is HUGE!

I'll probably be able to mount all the electrics, a battery, and the kitchen sink under there.

SF · « **Reply #3 on:** August 07, 2014, 09:44:30 AM »

I like the direction your going

goldarrow · « **Reply #4 on:** August 07, 2014, 10:00:19 AM »

looks like you have a 74 550, if 73 - it would be a 500. those gold inverted forks look so pretty. if stock pipes are not rusted out with holes, i'm interested.

calj737 · « **Reply #5 on:** August 07, 2014, 10:16:28 AM »

Quote from: goldarrow on August 07, 2014, 10:00:19 AM

looks like you have a 74 550, if 73 - it would be a 500. those gold inverted forks look so pretty. if stock pipes are not rusted out with holes, i'm interested.

May be a 500 frame but it's definitely a 550 motor. Side covers tell the story-

Jhelgesen · « **Reply #6 on:** August 07, 2014, 10:21:40 AM »

ID tag has a 73 build date and says CB550, probably an error on the title that says its a 73, but I'm not gonna fuss with the SC DMV over it

goldarrow · « **Reply #7 on:** August 07, 2014, 10:28:10 AM »

Quote from: Jhelgesen on August 07, 2014, 10:21:40 AM

ID tag has a 73 build date and says CB550, probably an error on the title that says its a 73, but I'm not gonna fuss with the SC DMV over it

if build date stamped on the neck is around second half of 73, then it's 74. it's good idea to know the correct year for the bike, just in case you ever need to consult parts fiche for certain motor/frame parts, and true that DMV won't care much to what you have, as long as appropriate fees are paid

Ravie · « **Reply #8 on:** August 07, 2014, 10:44:02 AM »

Reminds me of the title I have for my bike. When they guy I bought mine from got a reprint, they entered the VIN wrong and it's missing a digit. I think I'm going to ignore it for the sheer BS I'd probably have to go through to get it corrected. It'll be right on my Insurance, anyway.

Jhelgesen · « **Reply #9 on:** August 07, 2014, 10:48:22 AM »

Quote from: goldarrow on August 07, 2014, 10:00:19 AM

looks like you have a 74 550, if 73 - it would be a 500. those gold inverted forks look so pretty. if stock pipes are not rusted out with holes, i'm interested.

Two sets of stock pipes were patched together to make the one good set for the stock bike. I've still got the remaining front halves of the exhaust though. Check out those bars on the right hand bike, waaaaay cool.....not.

SOHC4 Cafe Racer Fan · « **Reply #10 on:** August 07, 2014, 10:52:38 AM »

Those bars are hilarious. Thanks for posting up a new thread. This is a great start. The CX tank rides a little on the high side. I wonder if you can modify the "c" mounts to let it sit a little lower and keep a flatter line flowing through the bike. I was curious as to where you harvested the reverse comstars (from your post in Rusty Olive/Cameron's thread), so thanks. Looking forward to how this turns out.

Jhelgesen · « **Reply #11 on:** August 07, 2014, 11:22:10 AM »

On the tank, yeah, its a bit high still.

I've ground down the seam on the frame and rewelded it, along with some hammer work on the bottom of the tank. I may try and form a small skirt around the bottom seam of the tank to try to flatten it to the lines of that I want, that and more hammering.

calj737 · « **Reply #12 on:** August 07, 2014, 11:44:59 AM »

Quote from: Jhelgesen on August 07, 2014, 10:21:40 AM

ID tag has a 73 build date and says CB550, probably an error on the title that says its a 73, but I'm not gonna fuss with the SC DMV over it

Disregard the build date and look at the VIN #. It will contain the model size within it.

RobbyD · « **Reply #13 on:** August 07, 2014, 12:06:26 PM »

Damn, great start man. Keep up the good work

quebec_monstro · « **Reply #14 on:** August 08, 2014, 09:06:27 AM »

Wow really interesting I'll be following up that thraed...keep up the good work

vfourfreak · « **Reply #15 on:** August 09, 2014, 09:28:50 AM »

These CBs look great with USD forks and modern brakes. Sort of indicates where Honda mght well have taken them if they continued their development beyond the early 80s.

Kev

Jhelgesen · « **Reply #16 on:** August 11, 2014, 10:02:53 AM »

Started a few sale threads to make space and gain some working funds.

http://forums.sohc4.net/index.php?topic=140213.0
http://forums.sohc4.net/index.php?topic=140181.msg1587551#msg1587551

Got the chain geometry in good shape to measure for spacers. Won't need offset sprockets after all.

Pulled the filler cap from an otherwise banged up tank to replace the boring one on the cx tank.

Jhelgesen · « **Reply #17 on:** August 18, 2014, 08:54:15 AM »

Got my MotoGPworks SS exhaust this Saturday. I have to say it a piece of art. Can't wait to hear it.

Bike is back on the stand, started playing with changing the lines of the bottom of the tank.

SOHC4 Cafe Racer Fan · « **Reply #18 on:** August 18, 2014, 09:42:17 AM »

I like how this is coming together. That CX500 tank is growing on me.

Don't forget to weld a hanger for your MGP pipe. It will keep that weight off the head exhaust ports.

Jhelgesen · « **Reply #19 on:** September 09, 2014, 05:29:39 AM »

My day job sends me to China a few times a year, so my last trip, I get a buddy to give me a hand hunting parts on their equivalent to ebay. Brought home some new parts, cb600 fender, shocks, two sets of clip ons, cnc levers, various brake parts, etc. With shipping the damage was under $200US and it all fit in my suitcase.

brandEn · « **Reply #20 on:** September 09, 2014, 07:10:25 AM »

Your off to a good start. I like the front end conversion.

jgreen · « **Reply #21 on:** September 09, 2014, 07:16:51 AM »

Excellent build thread. What type(s) of modifications, if any did you have to make to the steering stem and/or bearings to do the fork swap?

Thanks.

Jhelgesen · « **Reply #22 on:** September 09, 2014, 10:52:59 AM »

Quote from: jgreen on September 09, 2014, 07:16:51 AM

Excellent build thread. What type(s) of modifications, if any did you have to make to the steering stem and/or bearings to do the fork swap?

Thanks.

None, its a direct bolt in

I will need to trim the steering stops on the frame to gain a hair more travel.

seed608 · « **Reply #23 on:** September 09, 2014, 08:19:53 PM »

I like the progress, did you do anything to the rear shocks? I have read that some guys rebuild them out of the box

Sent from my iPad using Tapatalk

Jhelgesen · « **Reply #24 on:** September 11, 2014, 05:32:53 AM »

Nothing done to the rear shocks except bolt them on so far. Looking at a longer set to pick up on my next trip, raise the rear just a hair more.

Moosey · « **Reply #25 on:** October 17, 2014, 01:52:49 PM »

I have a 71 cb500 and am looking into getting comstars. I see you got yours off a 750a. Was a direct bolt in or did you have to change sproket, axle, spacer on the rear? I think I will have to use fork off of a costar bike for front (plan to keep older forks). Any input will be greatly appreciatd!!

Cougars750F0 · « **Reply #26 on:** October 17, 2014, 02:28:19 PM »

Quote from: Moosey on October 17, 2014, 01:52:49 PM

I have a 71 cb500 and am looking into getting comstars. I see you got yours off a 750a. Was a direct bolt in or did you have to change sproket, axle, spacer on the rear? I think I will have to use fork off of a costar bike for front (plan to keep older forks). Any input will be greatly appreciatd!!

Post to the Bikes & Parts wanted a lot of people prefer spokes on these old bikes if your spokes wheels are in good shape you may be able to trade. Here's the linkhttp://forums.sohc4.net/index.php?board=45.0

Jhelgesen · « **Reply #27 on:** October 17, 2014, 04:13:33 PM »

The rear wheel was a bolt on with the 550 axle. Going to try fitting a disc brake wheel next, so we'll see if that fits. I had to use the narrow sprocket carrier from a 750. I'll need a new spacer on the right side if I don't use the disc brake.

Don't know about the front axle since I have the cbr front end. I did find a yamaha front axle that is the right diameter and may save me some machining.

Lostboy Steve · « **Reply #28 on:** October 17, 2014, 06:34:27 PM »

That looks really sweet. So are you now going to have those adapters machined from aluminum?

Jhelgesen · « **Reply #29 on:** October 30, 2014, 07:07:26 AM »

Swapped the rear wheel to a 18" 750 sport disc brake wheel (instead of the 17" 750a drum brake wheel) Lost 10mm in tire width, but I'll live.

Using a rear caliper from a 750 sport, and a GL1000 disc (same part number as 750). I will need to narrow the caliper mount block to space the wheel correctly, take several mm off to center the wheel.

Front disc brake adapters arrived, fit perfect. Need to make axle spacers now. Found a yamaha front axle that was 15mm diameter, and longer than the CB, so I'll update my CAD for that one instead of making an axle from scratch.

Had to move the bike off the table for a bit while I work on another project, she has a pretty good stance.

SOHC4 Cafe Racer Fan · « **Reply #30 on:** October 30, 2014, 05:14:14 PM »

The stance and the tank look good.

Jhelgesen · « **Reply #31 on:** November 25, 2014, 09:32:09 AM »

Finished the front axle spacers after some slight tweaking on the lathe.

Now moving to the back.

Ended up fitting a 750 sport rear arm on the bike, perfect fit on the 550, bolted right on. Only issue is the wheel is a few mm off to the left, need to figure out how to space back right.

A big thank you to my lovely wife who surprised me with with a new drilled EBC rear rotor for the bike, so much nicer than the stock disc.

Jhelgesen · « **Reply #32 on:** December 28, 2014, 04:04:20 PM »

Wasn't happy with the raised front of the cx500 tank, so I formed some skirts to reshape the lower section, and installed the cap assembly.

Before

After

Bankerdanny · « **Reply #33 on:** December 29, 2014, 02:13:15 PM »

So they are purely cosmetic skirts, they didn't actually change the volume of the tank?

Jhelgesen · « **Reply #34 on:** December 29, 2014, 05:03:37 PM »

They are just cosmetic, but they greatly increase the space under the tank to hide wires, electronics, a tool kit, and maybe a few days worth of provisions.

greenjeans · « **Reply #35 on:** December 29, 2014, 05:16:04 PM »

Really like what you did with that tank. Great solution. can't wait to see this one back on the road.

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Author Topic: 73 racer build (Read 7972 times)