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Discussion Starter · #1 ·
First off hi. I am new here but not to Hondas. Currently I have a barn find 1970 CB450. It was in great shape and only 6,000 miles when I got it. I took it out for the first long (20 miles) ride and had some stuff happen. First, while I was riding it sorta felt like it was running out of gas once or twice but then ran fine after a second. (Float levels are perfect) Then when I pulled up in my driveway it dies never to restart again. It turns over with the starter and kicker but sounded like battery was weak. Charged battery to full. Still sounded like a weak battery. Checked right cylinder compression (cold engine closed throttle) and it was at 65. (I know I need to put in new pistons and rings) Starter sounded the same. Also checked for spark and there was none. Then checked the left cylinder and the motor turned over quite quickly and normally. Compression was 115 (closed throttle cold engine) and still no spark. I messed around today with it and noticed an exposed positive strap off of the battery. Taped it up and tried starting again. Smoke came off of the rectifier green wire and melted it. I know it needs a top end freshning. Question is why would there be no spark and could it be related to the near fire? I know I need to start checking outputs and resistance but the manual that I ordered three weeks ago along with other parts from oldbikebarn still haven't came in so figured if anyone here has had similar problems could save a little time. Thanks.
 

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Sensei
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My concern is that the rectifier Green (ground/battery negative) "smoked"...This means it was carrying the entire "load" from the bike (acting as the MAIN ground buss).... Clean ALL the joints on the ground cable and be sure it makes GOOD contact through the engine cases.... This could also be the ignition/lack of spark problem , the slow starter problem, etc. etc..... You'll need a new rectifier if you want the bike to charge the battery.... :shock: Steve
 

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Checking the compression with the throttle closed is a waste of time. You need to have the throttle full open and warm (if possible).
 

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Discussion Starter · #4 ·
I was looking at it a little today and noticed that the negative cable off of the battery is a little exposed and was in contact with a portion of the frame. Could that contact cause enough of a ground to catch the rectifier on fire?
 

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Sensei
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NO....The negative cable grounds to the frame......I believe it isn't well enough grounded... Clean the connections, and re-install the big loop on a clean rear motor-mount bolt.
 

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Discussion Starter · #6 ·
Ground strap appears good but the ground wire from the main harness has a pretty crappy connector. I am going to replace it as well as the rectifier and hopefully that will correct that problem. Oh also throttle open cold compression right side 140 psi left side 165 psi. I bet a good valve adjustment and a warm engine will bring those numbers up. Now I just need spark. :(
 

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Sensei
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The "kill" switches often go bad from corrosion "just sitting".... You can bypass and feed the coils ( BOTH black/white stripe wires) directly from the B+ to see if you get spark.... At least that could eliminate a bad "kill" and/or a bad ignition switch....
 
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