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Hello everyone, new to the forum and a new owner of a 1980 cx500. Got this bike for really cheap a few days ago and the only issue it had when I did a walk through was that it was running only with the choke and would rev so high when I take the choke off. This lead me to believe that it was either a a clogged pilot jet or an air leak. It started fine and engine sounded good with the choke on. I took the carbs out and cleaned them and cleaned out all the jets. I also replaced the throttle cables since those looked pretty frayed and gunky. I was stoked to get it started again and to my surprise when I turned the ignition key to the "on" position it attempts to start. It completely bypasses the starter switch and now it just cranks but will not run at all. What the heck did I do? I am new to tinkering and electrical terrifies me. Please help.
 

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1978 CX500 "The Grub", 1983 GL650I "Nimbus"
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11,444 Posts
Welcome to the forum!
The first thing I would check is the function of the start button. You might have contacts bridged by something. Set up you DMM to test resistance or continuity if you have an audible indicator. Find the ends of the leads from the switch, and following a wiring diagram, test continuity through the switch with the button depressed and not depressed.
 

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CX500EC Eurosport 1982
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81 Posts
Running ‘normal’ with choke on and then revving high with choke off makes me thing there is a vacuum leak in one or both of the intakes between carbs and cylinder head. But hey, at least it runs!
Are you still having the running problem?

The starter switch issue … hmmm … corrosion would normally lead to it stopping working entirely so my guess is that someone has deliberately bypassed that, probably when it stopped working due to corrosion, or perhaps just some hand-fisted repairs. multimeter testing will help but I think you’ll be looking at taking the R switchgear off and cleaning it up, maybe resoldering some of the original connections. Clean up any contacts with a bit of scotchbrite and wd40.
 

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How high is it revving?

Another possibility is that you've dropped the pull cables lock nut down the cable. When this happens 'idle' is about 4 grand.

It may slow down on the choke if it bogs from the rich mixture.

Attempting to start with an undercharged battery may have fused the starter switch contacts. Ditto for the starter solenoid itself. That has happened to me. The solenoid won't be your issue. When this happens it will crank with the key off.

Unless you have a wiring short I think you've fused the switch contacts.
 

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'84 CX650E that is evolving into a GL500
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17,728 Posts
Welcome to the forum. Please add your location and your bike's model and model year to your profile so that you don't have to remember to tell us every time and we don't have to keep asking when you forget (see Forum Settings link in my signature).

And welcome to the world of antique vehicle ownership (they own us, not the other way around). Your bike is about 4 decades old and (present problems aside) may or may not have had all of the maintenance necessary to keep it safe & reliable so it is highly recommended to download the Factory Shop Manual for your model (available through the CX Wiki - link in my signature) and go through all of the service procedures, regardless of whether your bike has reached the specified mileage.
I also recommend looking on all rubber parts with suspicion because rubber does not age gracefully. Check the date codes on your tires and replace them if they are over 5 years old no matter how good they look & feel (old rubber simply cannot flow around the irregularities in the asphalt well enough to grip, especially if it is cool or wet). If your bike still has the original rubber brake line(s) (should be replaced every 2 or 3 fluid changes = 5 or 6 years) I recommend shopping for modern stainless braided ones (they last practically forever and double the life of the fluid). And don't forget things like the rad hoses and the boot between the engine and swingarm (they can crack on the bottom where you don't see it).
 
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