Topic: '72 Honda CB500 K1 "Barn find"

[Felix]

About a month ago my doorbell rang, after answering the door a gentleman asked if the motorcycle on the parking place was mine. Why yes it is, that would be mine indeed.


(me being proud of finally getting my 400 running after 2 years of low-pace work)

I asked the man where the curiosity came from. The man told me that his elderly neighbor across the street had a similar bike in her garage, and that she was selling it because the owner had passed away a couple of months back. They'd prefer if it went to a enthusiast rather than some random buyer. The man assumed I were an enthusiast because of my bike (despite it being in a pretty rough condition). The same day I went to check it out and there it was, a very dusty CB500! I made it clear I was interested in the bike, gave my contact info and left. Last week I got a call that the brother of the owner was coming by to drop off the paperwork.
So, saturday was the day! I went to the house, made the deal and pushed the bike home! It was an agonizing 3 kms, since the bike had two flat tires, but that's where the bonding starts.



Here's how I found it, still in front of the garage where it stood still for a couple of years.

The mileage and some fly-poop.




In front of her new temporary home.

It's been preserved pretty well, the tank is completely rusted from the inside, hopefully still salvageable though. The chromework cleans up pretty nice, some tiny rusty spots at the front fender's usual place, same for the rear. Exhaust is in really good shape.


Rusted tank, would this be salvageable?

I put the battery of the 400 in there to check if she would turn over. All the lighting worked, but she didn't turn over. The solenoid gives a click and there's a little sound from the electric starter but it doesn't move completely.
After taking the tank of I noticed one of the levers on the carburettors being cracked, would this be a problem? It does move smoothly and everything, do I need to replace this or doesn't it offer any danger whatsoever?


Cracked lever thingy.



First I'm gonna try and get it running, from there on I'm going to restore it to running condition. I'm going to keep it as original looking as I found it, but replace parts where needed.
Since I don't have a big pool of money this project will be taking a while. I'm hoping to get advice where needed, and hopefully bring some smiles to people when this bike is finished!

[calj737]

I think ultimately you want to replace the cracked carburetor arm. But in the short term it should not prevent you from getting the bike started.

For the rusted tank, I would use electrolysis and extract as much rust using that technique as possible.

Very cool bike and very cool story.

[ekpent]

What brand of header is that, it has a nice look. The outside carb manifold rubber looks a little rough are those two cracks maybe ? That could affect the running if so.
    Never know when when of these machines may pop into your life 

[Tews19]

Try vinegar on the tank first... let soak for a week. You will be amazed.

[Felix]

Thanks for the advice, I'll try vinegar first. If that doesn't solve it I'll try electrolysis! Maybe in the long run I'll check eBay for a tank with original colors and preferable some aging marks on it. The complete exhaust system is a Marshall. Sadly the PO didn't have the 4-4 anymore but this exhaust looks way to nice to replace. And the rubber is in pretty decent shape, but it can't hurt replacing them in the long run.

[Felix]

After having the tank filled with vinegar and waiting for 2 weeks, I can't get it to open anymore. The hinge-lock system doesn't work anymore, any tips on getting it open without breaking stuff?

[calj737]

Have you drained the vinegar via petcock tap? If it's been sealed up, possibly the hinge had some rust that's gotten clogged up. Spray liberally with penetrating oil around the hinge and gently pry it up.

You don't need to seal the tank while it soaks for future reference. Perhaps just cover with plastic wrap and loop a rubber band over the filler neck.

[Felix]

The petcock doesn't work yet, so I'll have to drain the tank through the filler neck. And thanks for the advice, hopefully I won't need to de-rust another tank any time soon, though!

[calj737]

Can you not unscrew the petcock from the bottom of the tank?

[Felix]

I'll try that tomorrow.

[Felix]

In the last few months I haven't been able to do much. I recently moved it to a space I can work and store it in. Today I tried to get it running, but the starter engine wouldn't turn over and carb #4 was leaking. Kicking it didn't help either but it did make the spark plugs spark.
Now this is where I'm asking for advice. Would it be better to tear the entire thing apart, replace the parts that need replacing etc? Or would it be better to get the engine running and THEN start tearing it apart? The engine turns over fine with the kickstarter, all the electrics work except for the electric starter (which did turn over 6 months ago). I'm hoping some more experienced people could share their ideas on what's the best or smartest option right now.

[calj737]

Carb leak: may very easily be a stuck float valve from the debris that was in the tank (having worked its way into the bowl). Once motor is running, rapping on the carb body with a screwdriver handle often dislodges the debris and allows the float valve to reseat. Give that try when it's running...

Is it the solenoid or starter motor that's not spinning with the button START? Have you fully charged the battery, and be certain the KILL switch is in the RUN position.

[Felix]

It's the starter motor that's not turning, there is a audible click when I push the button. And killswitch was in RUN and I tried starting it with a portable battery thing that they use for starting cars.

[calj737]

With a good battery attached, try jumping a screwdriver across studs on solenoid. That should trip the starter motor. If not, the solenoid may be bad. But double check the terminals and yellow/red for good contact.

[Felix]

Thanks for the advice!

[Felix]

By now it might be obvious that this isn't going to be a high-paced build. I have gotten some stuff done, though.
The tank on the bike was too far gone to be usable and I found a tank on the internet for cheap, so I decided to buy it.



And last week I decided to rebuild the carbs, so I removed those from the bike. There were some screws that I couldn't get loose, though. Any tips on how to remove the screws without ruining the carbs? The carbs that did open up looked pretty clean for something that has been standing for almost 10 years, I guess that's a good sign.



And then there's some questions I have.

What's this spring for? It was attached to the rubber tubes at the bottom of the carbs. The other end was attached to the part where the throttle cables are attached.



Is this supposed to be flat, or is it broken/deformed?



And here is how it stands now! Now I just have to buy some parts.

[calj737]

Screws- these are not Phillips screws, they're JIS (Japanese Industrial Standard) and they are different which is why they get mangled when using a standard screw driver. You can buy JIS screw driver set (highly recommended) or bits, and you really should do so because you will use them repeatedly to service your bike.

Carbs - be very careful screwing the bowls on and off. It's soft alloy and screws will strip the body after repeated removal. Use some type of thread lube (AntiSieze) and just snug the screw enough, don't mash it in there.

Throttle cable linkage- that part you ask about flat/broken is supposed to be "parallel" guides to hold the "pull cable" from your throttle. There should be 2 throttle cables, a pull and a push. The pull rides in the top groove (now deformed) and locks in the key way on the end, and the push cable routes to the bottom of that same guide and locks in. The spring you found may well be the Prior Owner's homemade solution for a return spring or push cable. Interesting....

Inside of the carbs doesn't look bad, but they do require a complete internal strip down and cleaning for assurance. Ty to reuse the brass bits as they seldom require replacement and "rebuild kit" brass is often not as good as stock.