Topic: 1974 cb450 sudden death

[paulages]

okay, maybe death is a strong word.    sudden paralysis... just went through the carbs, points, etc... then wasted a couple of months trying to derust a tank beyond repair (too bad, as the exterior is perfect). new tank is lined and immaculate. petcock clean and flowing. strong spark.

the problem: it fires up fine and idles, responding well to throttling, but then suddenly dies as if you hit the kill switch. after this, it takes a few minutes to restart. once started it does the same thing. when not starting, the spark is still strong indicating the fuel system as the culprit. the gas in the tank is brand new 93 octane. i did leave gas in the carbs over those few months, but there is no varnish and the bowls and jets are clean as a whistle. however, when running, it sure is messy, blowing some serious cobwebs and other unhappy black #$%* out the back. i hope this is just old dust and soot in the pipes. i don't really know the bike's history, but it is really clean--no rust at all.

no airleaks at the intake, fuel appears to flow well... in other words, everything seems fine, but then it just dies. i'm sure i'll figure this out, but many head are better than one...

 

[333]

Sounds like maybe a dirty switch or connection somewhere.  Bike runs for a couple minutes, some dirt at a connection somewhere heats up and opens circuit, cools off and closes the circuit allowing you to start it up again.  Just a guess.

My first bike was one of these, a 74 CB450K.  It suffer from a couple of weird things over the time I had it.  One time I was tooling up the highway when it began to sputter.  I was doing my best to get it home.  I put my feet on the highway bars, with my left foot resting against the keys.  The sputtering stopped.  Apparently the ground for the ignition was going through the keyswitch, which had come loose.  This should not be.  The ground for the ignition comes through the points.  Yet...

And don't bother with 93 octane.  It calls for regular.

[paulages]

well as usual, the problem seems to have mostly fixed itself. i started it up tonight, and it ran fine, but quit on me once. once i got it running again, it ran well enough to take it around the block a few times. i don't think it's electrical, but i could be wrong. those twin carbs are tricky of not synced exactly right, so i need to double check them.

had a similar problem to what you are describing 333, on a cb350T.