Topic: 1972 CB500 - Rebuild Project

[Puffin]

I have one that I tried as a novelty.  The problem with mine is that the latch is a PITA to release.

It's a shame because I really wanted to use it... I didn't even care if it worked but when I filled the tank with water to check for leaks the thing just leaked out the top when I moved the tank about.  I just didn't want to take the risk on my newly painted tank.  .

[Restoration Fan]

So I'm over in another part of town this afternoon and i'm heading back to my van when out of the corner of my eye I see a small sign pointing down an alleyway indicating a Motorcycle Breakers.  Luckily I had my worn-out final Drive Flange in the back seat so I wander down fully expecting to walk back out the alleyway 2 minutes later with nothing lost but nothing gained.

Once there I was barely acknowledged by a rather short and incredibly grumpy old man who seemed nothing short of inconvenienced by the fact I'd come down to his place of business to potentially part with some money for something he made a living from selling.  Anyway, when I asked whether he had a 1970's CB500 he was breaking he surprisingly replied with "... only the back wheel".

The brief glimmer of hope that I initially had was soon quashed when he appeared from round back holding a rear wheel assembly that looked like had been outside in a puddle for the last 30 years.  Undeterred I asked for some tools to start taking the hub apart to examine the condition of the drive flange....

Despite acting like I'd asked him for a go on his teenage daughter, he eventually provided the necessary equipment and watched me for 20 minutes as I disassembled the rusted up and greasy pile of crap whilst trying not to get #$%* all over my best shirt and business attire.

When I finally got the drive flange off, and managed to convince him to part with an old rag to clean the part up, I found that somebody had already had the same problem as me but resolved the issue by machining a bronze bush that sat neatly inside the flange.

Eureka..!

"ll take this please"  I said
"No.. it's the whole wheel for $120 or nothing" he said
"but I only need this and the rest of the wheel is junk" I say
"fine I'll throw it in the skip" he said
"..........?" I said
"Ï told you it's $120 for the whole lot" he said
"yeh... but now I've just taken it apart for you?" I say
silence
"I'll give you $40 for the lot" says I
silence
"fine... hold onto it for another 30 years" I say

Then he starts putting the whole thing back together

....after another 10 minutes of childish exchange I start to walk away and he calls me back and we agree on $75 for the whole wheel.

I ended up with working drive flange, plus a spare hub, rim, cush rubbers and bearing retainer... all of which I don't need....  and he got lucky and made $75.

To be honest I would have spent more than that at a machine shop plus the arse of driving around town for the next couple of weeks so I'm generally happy with the outcome.  I had a number of breakers contact me to say they had spare flanges but they were all worn just like mine so I was running out of options.

Anyways... pictures below... all fits perfect and no more sprocket wobble...

LOL, ok this may be the post of the decade.  I had a good chuckle reading this one.

Just now catching up on this build but thank you very much for the documentation you're doing in your thread, Puffin.  I'm just at the point of reassembling the wheels on the 500 I'm working on and your build thread is going to come in very handy for me.  Well done.

Ron
 

[Puffin]

LOL, ok this may be the post of the decade.  I had a good chuckle reading this one.

Just now catching up on this build but thank you very much for the documentation you're doing in your thread, Puffin.  I'm just at the point of reassembling the wheels on the 500 I'm working on and your build thread is going to come in very handy for me.  Well done.

Ron

Thanks Ron.... and thank you as well    I spent so much time going through build threads, including your 750 thread, before I even started this project.  I'm not sure I would have had the confidence to start this without having access to other peoples experiences and advice.

I'm looking forward to seeing how your 500 & 550's turn out and good luck with your wheel assembly... I spent more time on that bloody wheel than I did rebuilding the whole engine???

[Puffin]

Installed new Stainless Steel brake lines up front.. 

If you want to keep the hard-line between the caliper and the lower hose for the authentic look don't forget that you need to get an adapter as the thread gauge is different.  It hides just behind the rubber grommet so you don't really see it.

New banjo bolts and copper washers installed as well

[Puffin]

Started back on the electrics.  Seems like a lot of people don't like this part but it's probably one of my favorites. 

I guess I find electrics logical rather than creative and that suits my personality... I'll fret and worry over a creative choice for ages but something like this I get stuck in with enthusiasm.

If you go back to the start of this build log you'll see I have already rebuilt the harness - it just needs wrapping but I'll be waiting until I have everything on the bike ready so I know for sure the length of all the wires around the rear of the bike.  As yet i haven't finalised the rear set up so i don't know where the rear indicators and tail light are going to be.

I replaced the original Regulator and Rectifier with a Combo unit that was pretty much plug-n-play.  I think it was a 'Ricks Electrical' unit.  i mounted it straight to the original electrical plate behind the left side cover.  It will get plenty of air there to keep cool.

[Puffin]

Managed to find a new loom complete with bulbs and rubbers the Idiot lights.... 

[Puffin]

Mounted my Dyna Coils coupled to new spark plugs and NGK caps..   I also have a new Dyna electronic ignition to replace the points and a new Motobatt Battery to go in.

These are basic modern upgrades that suit my needs, budget and how I'll be using the bike... you can go a lot further of course but I think these offer the best bang for buck, reliability and performance increases to suit my machine.

[RAFster122s]

Apply a ring of JB Weld epoxy to the neck of the tank to keep the gas from getting beneath the paint and ruining the paint on the tank.
 

[calj737]

Puffin - 2 things: have you test fit your battery and side cover (or is the location different from stock?) with the Reg/Rec mounted sideways? Its a good location, I just don't seem to recall enough room there with the stock battery box in place.

And I can't tell from the coil pictures, just making sure your 2/3 coil has the BLK/WHT wire to the top screw as you have on 1/4. And I only ask because I can't see, even though I suspect you have it right... But I always ask to make sure on things like that.

[Puffin]

Apply a ring of JB Weld epoxy to the neck of the tank to keep the gas from getting beneath the paint and ruining the paint on the tank.
 

Good tip thanks.. I was wondering about how to stop the gas getting under the paint.  Should have the tank back in a couple of days.

Puffin - 2 things: have you test fit your battery and side cover (or is the location different from stock?) with the Reg/Rec mounted sideways? Its a good location, I just don't seem to recall enough room there with the stock battery box in place.

And I can't tell from the coil pictures, just making sure your 2/3 coil has the BLK/WHT wire to the top screw as you have on 1/4. And I only ask because I can't see, even though I suspect you have it right... But I always ask to make sure on things like that.

1 - Yes have test fit and everything fits perfectly.  Everything is in the stock position.  There is about a  5-10mm gap between the air-box and the Reg-Rectifier Unit. (see below)
2 - Double checked and BLK/WHT wire is on the top screw on both coils.

[Puffin]

My new battery arrived...

Model# -  Motobatt MB12U

It's an AGM battery, it has multiple terminals and a set of terminal adaptors so you can mount your cables and accessories as you like.  It also has a small tray to increase the height if you need it.

I also bought a matching Motobatt "Little Boy" charger and maintainer which came with a quick-connector so you don't have to muck about if you need to charge your battery or story the bike for a while. 

It's pretty yellow but you can't see it behind the covers.

[Puffin]

So I have a couple of decisions to make regarding the airbox cover.

I have no seat and so I plan on making a new seatpan and then getting a seat made by an upholsterer.  With the stock airbox however I need to make sure there is enough room between the top of the airbox and the base of the seat so the bike can breathe.

The stock CB500 came with a lid that also acted as a tool tray but this sticks up higher than the frame which is going to be a problem.

[Puffin]

For some reason I also have what I believe to be a CB550 airbox... the top of this is slightly different in that it has a metal lid with a rubber 'funnel' attachment that bolts to an extra couple of brackets inside the air box.

This also sits higher than the frame but the rubber funnel is removable.

[Puffin]

I figured that I could use the 550 lid without the attachment which would effectively be the same as using the original tool tray because the openings are the same size and in the same position over the air filter. 

In theory this should effectively act the same as the stock set-up.   I'm going to have to tune the bike from scratch anyway so any slight changes due to this set up should be easily accounted for.

I'm going to find a piece of metal mesh like the original and rivet or epoxy it over the hole to keep out any larger pieces of debris.

I installed the 550 brackets, re-glued the foam seal and gave it a lick of paint.

I'd be interested to hear any thoughts about this idea.  The result is that the opening to the airbox now sits lower than the frame so there will be a gap between the airbox lid and my new seat pan to allow airflow.

[Puffin]

Couple more pictures

[Puffin]

Popped down to see how my tank is getting on and couldn't resist posting a few pictures...  Final clear coat is waiting for a light sand and a buff then it's all ready.

Been thinking of various colour schemes for the last 12 months and I must have changed my mind 50 times but in the end only one colour was sticking in my mind which was......   Honda Repsol Orange. 

Given the rest of the bike is Matt Black and Chrome I think this is gonna look awesome..

Fun Fact:   Repsol first got into Motorbike GP racing in 1971 which was the same year the CB500 was introduced... 

To be honest I only learnt this yesterday so it's more of a coincidence than an official tribute but it's gonna make a good story if anybody goes "Hey man nice tank colour" or "why the hell did you paint your bike Orange bro?".

[calj737]

A Repsol livery would look killer on that ride!

[Restoration Fan]

Beautiful paint, Puffin!  Looking good, man.

[RAFster122s]

Very nice Puffin! The Repsol Orange really pops. I like it.
A top coat of a urethane clear like the Spraymax 2k would protect the paint from gas.

David

[Puffin]

Tank is done and all assembled.... Looks amazing with white badges and the new gas cap

[Puffin]

My phone camera pictures don't really do it justice but adding the tank really pulled it together... the bike really is starting to look so cool...

I find myself standing in the garage just staring at it 

[Puffin]

Going back a step I have also finished off the electrics.

I wrapped up the wiring loom using some TESA cloth tape...  It's really easy to use and made a really nice neat job.  Held it on the bike using extra wide cable ties and used Dielectric grease on all the connections to prevent corrosion later.

[Puffin]

The Electronic ignition attaches to the Black & White switched wire from the coils using the supplied splicing device.

I static timed the ignition using a test light with one lead grounded to the body and the other attached to the corresponding -ve coil wire.  The difference with the Dyna ignition to standard points is that you have to time it to full advance so make sure you read the instructions carefully.

It's a little fiddly holding the cam to full advance whilst looking through the view hole and rotating the engine all at the same time but I got the hang of it pretty quickly.

[Puffin]

I am so glad I labelled each cable back at the start of this project... it saved me sooooooo much time.  There was only really the idiot lights than needed connecting and these were pretty straight forward.

I only had to de-bug the horn and the oil pressure light.

I was puzzled by the horn not working as it was working fine when I mocked everything up at the start?  A check of the wiring diagram however showed that the horn grounds at the switch and in a moment of clarity I realised that my new handlebars were powder coated as opposed to the chrome ones I used originally.  A bit of sandpaper and I cleared some paint off at the switch and again at the clamps and the thing fires every time.

I had bought a tiny black horn that I was going to use as a replacement but the sound it made was just so quiet I doubt anybody sat in a car would have heard it.. the original one however sounds like a truck horn ... it's ridiculously good and I kind dig it's retro vibe so it stays.

[Puffin]

My other problem was the oil pressure light not coming on when I turned on the ignition..

It was easy to diagnose that the oil pressure switch was faulty.  With no oil pressure the switch should be closed or ''on" so there should be continuity between the little metal part at the top where the wire attaches and the metal body of the switch which goes to ground.  No continuity means the switch is stuck open which means the circuit is not complete which means your oil light will not come on.

Rather than pay over-the odds for an original switch you can search the part number and it lists a load of Honda Cars that use the same switch... I think Preludes, Civics and Accords for example. 

I picked a new switch up for $9 NZ which is crazy cheap.

If you are going non-original the thing you need to watch is thread types and the actual pressure the switch activates.  I believe the original was an M10 x 1.0 taper thread that activates around 7psi....?

My switch activates around 5.5psi and the thread was 1/8 GAS (I think that is a British non-tapered type thread?).  Either way it fits just fine..  I did use some plumbers tape (teflon or PTFE tape) around the threads as a precaution.

Apparently this switch fits all the cars in the photo if that helps anybody...