Author Topic: 71 CB500 track build  (Read 1918 times)

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Offline Aussie500

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71 CB500 track build
« on: June 18, 2018, 03:36:41 am »
After doing a few racing rounds on a CBR250r (MC19) I couldn't take my eyes off the of CB350's and one CB500 that were there. i ended up spotting a CB500 that came up on one of the local Cafe' Racer pages. It was a project that never started after the enormity of the project set in. My mate already had a few parts ,including a frame sitting around due to the engine out of it expiring so all we really needed was the engine.

The parts in the photos are donor parts from what was sitting around. There were some carbs from a CB750 sitting around so we offered them up but 1 & 4 fouled with the stock tank. To get around this I am using the tank in the photo and I am making a mount to raise the rear to clear the carbs. My mate said the 750 carbs are a good replacement for the stock ones without the cost of the CR's and I believe i read someone else on here saying the same?

Next steps are:
make rear mount for tank
mount seat
temporarily mount engine in frame to make-up rear sets and check fuel tap on tank doesn't clash with carbs or anything else.

Suggestions and input on anything more than welcome.
« Last Edit: June 18, 2018, 03:38:52 am by Aussie500 »

Offline Aussie500

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Re: 71 CB500 track build
« Reply #1 on: June 18, 2018, 03:40:59 am »
Wheels
« Last Edit: June 18, 2018, 03:44:27 am by Aussie500 »

Offline Aussie500

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Re: 71 CB500 track build
« Reply #2 on: June 18, 2018, 03:43:42 am »
Forks and triple clamps

Offline Rocketman

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Re: 71 CB500 track build
« Reply #3 on: June 18, 2018, 03:20:33 pm »
Welcome to the forum!  I'm currently racing a CB550 so will be following your build.  You may find the CB750 carbs hard to jet properly for your purpose.  I tried to make them work, but ultimately gave up and went with CR29's.  Be sure to check out bwaller's "lets go roadracing...continuing saga" for inspiration.

Offline Aussie500

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Re: 71 CB500 track build
« Reply #4 on: June 18, 2018, 09:36:46 pm »
Welcome to the forum!  I'm currently racing a CB550 so will be following your build.  You may find the CB750 carbs hard to jet properly for your purpose.  I tried to make them work, but ultimately gave up and went with CR29's.  Be sure to check out bwaller's "lets go roadracing...continuing saga" for inspiration.

Thanks Rocketman. I don't mind paying the money if something is worth it and it saves headaches along the way. Will check out the post

Offline blacksmith1

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Re: 71 CB500 track build
« Reply #5 on: June 26, 2018, 02:26:37 am »
good gear mate, what style of racing are you doing

Offline Aussie500

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Re: 71 CB500 track build
« Reply #6 on: June 26, 2018, 03:19:12 am »
good gear mate, what style of racing are you doing

Hi Blacksmith,

Building it to race Period 4 500cc historic road racing here in Western Australia. Should be getting the engine pulled apart next week for assessment and parts ordering. Haven't had much opportunity the last week.

Offline Aussie500

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Re: 71 CB500 track build
« Reply #7 on: June 28, 2018, 04:22:23 am »
Engine tear down happened last night and thankfully no nasties were to be seen. All the exteriors went into the parts washer ready for machining and vapour blasting.
« Last Edit: June 28, 2018, 04:32:01 am by Aussie500 »

Offline MRieck

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Re: 71 CB500 track build
« Reply #8 on: June 28, 2018, 04:55:40 am »
Don't want to be nosy but what's the plan for the engine?   
Owner of the "Million Dollar CB"

Offline Aussie500

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Re: 71 CB500 track build
« Reply #9 on: June 28, 2018, 05:10:10 am »
Don't want to be nosy but what's the plan for the engine?

Not nosy at all, but very polite.

i suppose going mid $$$ range with new internals. Davies pistons, webcam (I believe), oversized valves , lighter valve springs, head porting, new timing chain etc.

I admit I am relying on my mate/ mechanic a fair bit and going with his experience and learning along the way. He is quite handy with a CB and races his 350 at a rate of knots. Pretty sure he's looking forward to racing it as much as me.

Offline blacksmith1

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Re: 71 CB500 track build
« Reply #10 on: July 03, 2018, 02:44:20 am »
great job mate,always loved the 500,good luck

Offline Aussie500

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Re: 71 CB500 track build
« Reply #11 on: July 03, 2018, 03:57:22 am »
great job mate,always loved the 500,good luck

Cheers Blacksmith, slow progress the last couple of weeks but hopefully should be picking up from next week.

Offline Aussie500

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Re: 71 CB500 track build
« Reply #12 on: July 06, 2018, 03:08:50 am »
Slow progress is still progress.

We were going to use 750 carbs but not sure not. either way when we fitted them up carb 1 & 4 fouled the tank when all the way open. To counteract that I extended the mount for the tank and made a bracket for it to sit higher. Used rubber mounts that are used to mount the front the front of MC19/22 tanks.

At least now whatever we decide to do we will have the room. Plus i really like the way the tank sits now the back is higher.


Offline Aussie500

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Re: 71 CB500 track build
« Reply #13 on: July 23, 2018, 03:54:26 am »
Small milestone achieved by finishing off the tab for the sprocket/heel and adding a brace to strengthen rear shock area that doubles as seat mount. I'm no professional welder but I've seen alot worse. the aluminium bracket in the middle was the previous rear seat mount. Just need to make up the front fender and frame is ready for tear down and clean up prior to painting.
« Last Edit: July 23, 2018, 03:59:48 am by Aussie500 »

Offline calj737

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Re: 71 CB500 track build
« Reply #14 on: July 23, 2018, 05:24:57 am »
With the tank modification, you're pushing fuel away from the petcock... just a "caveat" for you.

On your swing arm welds, you need more heat. Cold toes are weak welds. The edges of your welds want to be fully fused into the parent metal. Rounded up, or "humpy" welds are indication of lack of penetration/too low amperage. You can run your TIG torch back over them now, no filler, and wash them in hotter for stronger results.
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Offline turboguzzi

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Re: 71 CB500 track build
« Reply #15 on: July 23, 2018, 06:00:56 am »
raced my 500/4 for 4 seasons without that bridge between shocks without problems, ditto for the swingarm reinforcement.
would look for ways to add rigidity to the central frame rather than extremities of it.... :)
looks to me like unnecessary adding of weight
search for my build thread for pics.
the one frame mode that to my aerospace engineering trained mind added most rigidity was a head steady for the motor.
 

Offline Aussie500

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Re: 71 CB500 track build
« Reply #16 on: July 23, 2018, 02:52:49 pm »
With the tank modification, you're pushing fuel away from the petcock... just a "caveat" for you.

On your swing arm welds, you need more heat. Cold toes are weak welds. The edges of your welds want to be fully fused into the parent metal. Rounded up, or "humpy" welds are indication of lack of penetration/too low amperage. You can run your TIG torch back over them now, no filler, and wash them in hotter for stronger results.

Thanks for the reply as this is exactly why I am here. I will be giving the frame to a welder friend to look over and inspect my work. I was going to get him to do them but I like the idea of learning and doing myself especially on non-structural parts.

Would you say the tank is definitely a problem or something to be mindful of in regards to fuel levels etc?

Thanks Adam
« Last Edit: July 23, 2018, 03:00:55 pm by Aussie500 »

Offline Aussie500

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Re: 71 CB500 track build
« Reply #17 on: July 23, 2018, 02:59:50 pm »
raced my 500/4 for 4 seasons without that bridge between shocks without problems, ditto for the swingarm reinforcement.
would look for ways to add rigidity to the central frame rather than extremities of it.... :)
looks to me like unnecessary adding of weight
search for my build thread for pics.
the one frame mode that to my aerospace engineering trained mind added most rigidity was a head steady for the motor.
 

Thanks for taking the time to look at the build as feedback is what I'm looking for. I will look over your build to see how you mounted your seat and did your bracing. The swingarm mod isn't for reinforcing it is to mount the sprocket guard we need to run (see attached).

Thanks again TG.

Offline calj737

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Re: 71 CB500 track build
« Reply #18 on: July 23, 2018, 04:37:33 pm »
Would you say the tank is definitely a problem or something to be mindful of in regards to fuel levels etc?
I would not be able to say without paying a level on the underside. It should definitely not run "forward" from the rear if you want to insure you keep fuel to the petcock as you run low. Also, gas sloshing forward under braking would be problematic for the carbs if the level were down, you'd starve them potentially until you got back on the throttle.

Just something to keep an eye on  :)

PS - Tell your Welder Mate that a Certified Internet Welding Inspector critiqued your beads. That should give him a chuckle  ;D
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Offline Gurp

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Re: 71 CB500 track build
« Reply #19 on: July 23, 2018, 06:03:56 pm »
Following 👀👀👀
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slow Progress 74 cb550.

Poor boy chop 73 CB500 chop

Offline Aussie500

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Re: 71 CB500 track build
« Reply #20 on: July 23, 2018, 09:40:33 pm »
Would you say the tank is definitely a problem or something to be mindful of in regards to fuel levels etc?
I would not be able to say without paying a level on the underside. It should definitely not run "forward" from the rear if you want to insure you keep fuel to the petcock as you run low. Also, gas sloshing forward under braking would be problematic for the carbs if the level were down, you'd starve them potentially until you got back on the throttle.

Just something to keep an eye on  :)

PS - Tell your Welder Mate that a Certified Internet Welding Inspector critiqued your beads. That should give him a chuckle  ;D

haha. He's pretty meticulous so I'm sure he will agree with you And give me a further talking down.

Offline 754

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Re: 71 CB500 track build
« Reply #21 on: July 23, 2018, 10:43:44 pm »
The 750 carbs   are they round top ?
 The PD type won't have clearance problems to the tank, in most cases.
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Offline Aussie500

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Re: 71 CB500 track build
« Reply #22 on: July 24, 2018, 04:51:54 am »
The 750 carbs   are they round top ?
 The PD type won't have clearance problems to the tank, in most cases.

yeah they were round tops but have gone away from them now.

Offline Aussie500

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Re: 71 CB500 track build
« Reply #23 on: August 11, 2018, 04:30:48 am »
Slow progress is progress.

Got the front fender made and fitted. I have about 15mm clearance in between the fender and tyre with room to go up another 25mm.

Also mounted the rear sprocket guard and stand pick-ups.

All ready for tear down, paint & rebuilding

Offline Aussie500

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Re: 71 CB500 track build
« Reply #24 on: January 13, 2019, 03:41:56 am »
Finally some progress on the 500.

I was going to paint the frame but then I started doing a bit of research into Cerakote. Very thin so it won’t hide irregularities like paint and powder but is meant to have excellent abrasion and chemical resistance so thought I’d give it a try.

Really happy with the satin black and I think the finish is well suited to a period racer. Also had the swing arm, trees and engine mounts done.

Just waiting on a couple of things from CMS and the platers and it can start going back together.

 

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