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Discussion Starter · #1 ·
I picked up a 79 cx500 custom that was not running and had the carbs off. I rebuilt the carbs and reinstalled them. I also adjusted the valves for good measure. I am pretty confident in my work as I was a small engine mechanic for a few years and have been working on engines since before I could drive.

I have verified compression, spark and fuel delivery but cannot get the engine to fire. Even if I squirt starting fluid into the intake or directly into the cylinders.

Any suggestions or assistance would be greatly appreciated.
 

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Sounds like he spark is not being delivered at the right time.
Check timing, maybe with a timing light???
Check the pink and yellow wire from the CDI to the coils, pink to right, yellow to left.
 

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Discussion Starter · #3 ·
I thought that also, but the engine has not been apart and my understanding is the timing is pretty hard to upset on these engines. I can throw a timing light on it when cranking to see what is going on.
The pink and yellow wires are correct and the spark is strong and blue when I pull the plugs and ground them while cranking.
 

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Discussion Starter · #5 ·
What are your compression readings? How did you verify fuel delivery?
Compression is low. About 100 on left and 130 on right. However, the starting fluid should at least pop even with low compression.
I have confirmed there is fuel delivery. Non-vacuum petcock, glass fuel filter and the plugs are slightly wet. Not soaked but damp.
 

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All elements seem to be in place for at least a pop. As O O says, the timing might be off. It wouldn't hurt to switch the coil connections and see what happens.
 

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"Can it breathe? Maybe the airfilter is blocked if you have spark and fuel. The compression should also be enough to start."

Yea, like in an old Eddie Murphy movie he stuffs a banana in a car tailpipe and it won't start.

Claw, did you check for bananas in your mufflers?
 

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You may mock, but if it can't inhale it can't ignite. My mower actually did this a while back when a water leak in the back shed wet its airfilter,

This will also cause low compression readings.

Of course, so will a worn out motor or being off the road for years.

Of course, if the filter has been removed to spray the ether ....
 

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Discussion Starter · #14 ·
Thank you all for the suggestions. I am pretty new to forums and really appreciate the outpouring of assistance.

I have done all of the above EXCEPT disconnected the kill switch. However, I did pull the plugs and ground them to the exhaust flanges and observed the spark during cranking. The spark was really strong and blue. This leads me to believe the kill switch is not an issue.

I also checked the resistance for the stator as I found in another thread. Everything checks out (1/5,2/5,3/5, etc.) except the voltage from the white wire seems low during cranking. According to what I found, it should be 100V and I don't think it is. I only have an inexpensive analog meter, but am going to borrow/buy a digital one for more precise readings.

Again, thanks to all.
 

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How are you getting the ether into it? If through the vacuum gauge ports they are massive vacuum leaks.

And that air filter?

Open the fuel drains in case the fuel in the bowls is stale and let them run a little to flush and to verify that your fuel actually keeps flowing. How old is the fuel in the tank?

Check the white wire voltage when you can but I don't think the spark is your problem.
 

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You may mock, but if it can't inhale it can't ignite. My mower actually did this a while back when a water leak in the back shed wet its airfilter,

This will also cause low compression readings.

Of course, so will a worn out motor or being off the road for years.



Of course, if the filter has been removed to spray the ether ....
Phreak, no mocking intended.
OK, there are likely no bananas involved, but my point was that something could be blocking air flow in the exhaust system.

 

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Valve timing can be off a little and even give good compression readings. I had a similar problem on a kaw 550 Spectre.
 

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I also checked the resistance for the stator as I found in another thread. Everything checks out (1/5,2/5,3/5, etc.) except the voltage from the white wire seems low during cranking. According to what I found, it should be 100V and I don't think it is. I only have an inexpensive analog meter, but am going to borrow/buy a digital one for more precise readings.
Note that the voltage output from the white and blue wires is AC. It will give weird readings on a meter set to vDC.


R
 

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Discussion Starter · #19 ·
Spraying straight into intake boot through air box with filter removed.
Gas is fresh. I have removed and cleaned the carbs twice.

How are you getting the ether into it? If through the vacuum gauge ports they are massive vacuum leaks.

And that air filter?

Open the fuel drains in case the fuel in the bowls is stale and let them run a little to flush and to verify that your fuel actually keeps flowing. How old is the fuel in the tank?

Check the white wire voltage when you can but I don't think the spark is your problem.
 

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Discussion Starter · #20 ·
Thanks for that info. I am pretty sure I had the meter set on vDC.

Note that the voltage output from the white and blue wires is AC. It will give weird readings on a meter set to vDC.


R
 
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