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CB450 switch not cranking the engine

JTruest

Member
Joined
Feb 25, 2022
Total Posts
25
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0
Location
BEVERLY
I have a 74 CB450 K7 and I just reassembled my engine and put it back in the frame but after connecting the starting motor cables to the post of the starting motor and the post of the starter solenoid, I hit the switch and get nothing. I have tested the starting motor with direct 12V power and it spins and cranks the engine. I have also tested the solenoid and it's working correctly.

I turn the key and get 12V at the switch with no change when I press the button. I took the switch assembly apart and made sure nothing was broken but all looks fine. I also tested the Yellow/Red wire that goes up to the switch and get consistent 12V power. Maybe a faulty switch? Am I connecting the big black post cables coming out of the gearbox incorrectly? Is there any other way to override the switch to check to see if that needs replacing?

Help would be greatly appreciated. Thanks!
 
Pictures, can't see anything other than what you've described so it's hard to say. Where are you testing the yellow with red? It's a wire that needs to be grounded to make the solenoid work which then sends the high amperage 12v to the starter. Solenoid has to be correctly connected and the handlebars have to have the little ground jumper in order to provide ground for the yellow with red a ground to make the solenoid work.
 
I had a similar thing happen on my 67 K0. The solenoid would click when I pushed the start button, the Neutral light was on, and if I jumped the two larger terminals on the solenoid with a screwdriver it cranked fine. I took the solenoid off the bike and took the two screws out that hold the top and the lower, bowl like part together and cleaned the copper contact plate surfaces and the copper surfaces inside as well with a Dremel and a bit of carb cleaner.. Blew it dry, put it together, hooked it up and it works just fine. I guess 50 years of grime was too much in there.
 
I recently replaced the solenoid on my K5 after I realized it did not want to come apart. I did try though. A new solenoid was really cheap and it worked which was a surprise as it was a cheap knock off from Fleabay.
 
Had the same, make sure that your right-hand controle is properly grounded; the handlebar itself is isolated from the frame by the rubber damper cones (was my own assumption). Test it by connecting the control with an auxiliary wire to a place on the bike of which you know it's properly grounding.
Let us know :)
 
After struggling with electrical issues I installed a permanent ground wire from under the nut on the bottom of one of the handlebar mounts to the frame where the battery ground connects. It may be unnecessary but now I know the bars are grounded. On the CB450K0 the instrument cluster is not grounded in a way that made me confident so I ran a wire from it back to the same place on the frame.
 
Smart move, I did exactly the same on the bomber.

Am I reading it right that this precaution unfortunately didn't or doesn't solve the issue?
 
^^^And that was a good move, as Jim says you can't have too many grounds. The older bikes initially depended on the control cables for handlebar ground, some even relied on the speedo and tach cables which eventually caused issues with the gauges. They later added the short ground wire from the handlebar mount to the gauge bracket mount stud under the top bridge.

honda-cb350k3-super-sport-1971-usa-speedometertachometer_bighu0028f4019_dd1b.jpg

#19 below
honda-cb350k4-super-sport-1972-usa-speedometer-tachometer_bigma000148f19_025b.jpg

https://www.cmsnl.com/honda-cb350k4-super-sport-1972-usa_model433/cord-switchearth_32111319000/
 
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