$200 '72 CB450

RabbitSkull

New Member
I just purchased this 72 450 for $200 because the car dealer that had it fired his motorcycle mechanic and couldn't get it working. I actually bought a CB750 to ride and this one was an afterthought. Turns out I am enjoying working on this one a lot more than my 750.

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The dealer had purchased a new throttle cable and clutch cable. and before he fired his mechanic he had the carbs rebuilt. I don't know what condition they are in, but hopefully it was all done right.

I got the thing running in about 15 minutes by simply cleaning out fuel lines, spraying some fuel into the carbs and giving it a few kickstarts. It fired on about the 6th kick or so.

The next day I started looking at the clutch, and realized it wasn't disengaging at all. I played around with the adjustments, but no luck. I even pulled the cable out all the way with some vise grips, but it wasn't doing anything productive. After looking at some exploded parts diagrams and taking the cover off of the clutch cam arm I realized it was missing the ball bearing. I just happened to have an old bearing that had 5/16" balls in it, so I pressed one out and everything worked perfectly.

I realized that i had stumbled upon a pretty good deal. The dealer said he had about 400 in it plus parts that I have receipts for equaling another $150. So I got his $550 investment for $200 all because he didn't know how to read a parts diagram. ---BONUS!!!---
 
So, today its the rearsets...

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I have a ton of this 1"X.75" SS bar left over from a job a few years back.

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After some turning and milling

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Now with my bracket and a linkage

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Mounted to the bike

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I decided to go the easy route and not make a linkage for shifting just yet. I'm going to make a longer shift pedal that matches my brake but I'm just going to have it turned around giving me a simple race pattern. I kept my programs so I can make it later if I need to, but for now the easy way works.
 
Wow, its been a while. After a crazy busy semester Im finally getting back to work on the little twin.

As you can see I have done quite a bit here and there. I kinda stopped posting because the progress was so slow, but now its time to kick it all back into high gear.

Stripped and aluminum-coated frame

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Here is one with everything mocked up.
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a close-up of my battery box...
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Here comes the fun part...

It got it running with almost no work. Almost no work consisting of:

Boiling and rebuilding the carbs
Cleaning out the rusty fuel tank by the nuts/bolts method and tons of rinsing followed by an internal media blast and more rinsing.
Spraying a bit of fuel directly into the carbs
Kicking it over!

It fired on the first kick and ran on the second. Nedless to say I was extremely excited.

Now I have an issue. After riding a few hundred yards it died. I pushed it back and found that I have a spark issue. I changed my points, trimmed my plug wires and installed new spark plug caps. I had my condensers checked and everything was good. I get irratic spark still and have no clue what to do. Points gap looks good, battery is good.(Iv'e tried both my cells and a new stock batt.)

Any ideas, what am i missing? This is my first ground up project so I am extremely new to this. Any help would be greatly appreciated.
 
2 things... Sweet bike, and I agree with Jay, you should totally sell those rear sets!
 
Thanks for the compliments, but those rearsets aren't the finished product. I just threw them together for mock up purposes. Ill add some pics on my real design once I get the thing running. Im getting it running and all set up before I add the wow factor parts I'm working on.
 
It's clearly too late now, but I would've ridden that beast just the way it was! I love the barn find look.
 
UPDATE...

I just found an issue.
I get 14v through the electrical system with a Charger/Starter connected, but once I turn the ignition on it drops to 7.5 volts. when I try to start it, it turns over nicely, but there is little to know spark and no firing. What are the possible issues causing this?
 
RabbitSkull said:
UPDATE...

I just found an issue.
I get 14v through the electrical system with a Charger/Starter connected, but once I turn the ignition on it drops to 7.5 volts. when I try to start it, it turns over nicely, but there is little to know spark and no firing. What are the possible issues causing this?


It's probably just a bad battery.
 
Im not using a battery. I thought my battery may have been weak, so i just hooked my engine starter straight to the leads. I had it running 12v@40a straight into the system. I dont know whats causing the system to drop half the voltage when the key is turned.
 
First person to solve this with me gets my rearsets when I tear them off!!! I am desperate and have no clue where to start with testing components.
 
RabbitSkull said:
Im not using a battery. I thought my battery may have been weak, so i just hooked my engine starter straight to the leads. I had it running 12v@40a straight into the system. I dont know whats causing the system to drop half the voltage when the key is turned.


Are you measuring voltage at the leads?
 
A couple of things you can try...

- Disconnect wires from the ignition one by one to see if you have a drain somewhere. (possibly a short in the lights?)
- Not sure if this bike has a starter relay, but see if it does, and see if you can't test it. That relay _should_ kill the power to everything on the bike (lights, etc...) to allow optimum cranking amps to the starter and coil packs.

If you're running straight into the starter with those leads, then you're probably bypassing that relay. So if the relay is the culprit, you need to either A) test / replace it.. B) try and test the system with the charger / starter hooked up to the battery wires.. C) replace the battery and go from there...

Option C is going to be your best thing to start with I would think. That way you're getting a complete and proper test.
 
RabbitSkull said:
First person to solve this with me gets my rearsets when I tear them off!!! I am desperate and have no clue where to start with testing components.

gremlins. now gimme those rear sets!
 
I remember my bike had the same problem. The battery was brand new, measured about 13-14 volts, then when I cranked it, it dropped to about 8 volts.

The problem was dirty electrical connections. Get some CRC Electronic cleaner at any auto store then spray them on your electrical connections. Especially the coil packs.
 
Thanks guys, ill try these ideas out. Im thinking it is a drain somewhere, and if so hopefully ill narrow it down today. It cant hurt to throw some cleaner on the connectors either. Ill get back, hopefully with some results later.
 
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