gs450 dead cylinder

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Hello All
I am new to the site, and an amateur at repairs, but I love my gs's (I have 5) so I gotta learn. Searching the site got me lots of answers to problems with my other bikes, but this one is driving me,,,,,,. It is a 1982 gs450T with 4,000 miles. I bouight it from a guy who stuck it in the back yard because he couldn't get the left cylinder to fire. I changed the plug and all the fluids when I got it and it ran for 2 years no problem. Now it is my turn to experience his frustration.
It was running fine, and then the cylinder just stopped taking spark. I have cleaned the carbs within an inch of their lives, new o-rings, new coil, new wire, new plug, new cdi, new rectifier, new pickup coils, new gas, but no fire. Is there a fuse in the harness somewhere I am missing or a solenoid or something? Any input would be appreciated.

[Dave8338]

Cut about 1/2" inch off the plug wire and reinstall the plug cap. My thought is that there is spark everywhere...except through the cap. This is not an unlikely problem. If that doesn't fix it, try another wire from another (known good) coil and see what happens.

(just reread your post...swap out the plug cap and check the valves)

OH, I almost forgot...WELCOME TO THE GSR!!!!! If it can't be figured out here, sell it for parts!
Don't worry...we'll figure it out.

Basscliff, it's your turn...

[reddirtrider]

Do you have battery voltage to the coil in question? Clean the contacts after checking.

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Thank you for the quick responses. I checked the valves. Good compression. taking fuel. I will check the voltage into the coil this evening, and get back to you.
Thanks again

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reddirtrider you hit it on the head. Checked for voltage on the coil and ended up tracing the wiring all the way back into the headlight pot where one of the power supply leads (orange/white stripe) had corroded inside the connector. Cleaned it up and "amazing" there was spark
Thanks

BTW my search in the old posts to find a solution for the 450 also found a solution for my 1980 gs850g. I rebuilt the carbs 3 times trying to solve the flooding problem in number 2 cylinder, without luck, but someone said their petcock was leaking through the vacuum hose, and I realized the vacuum tube is right beside number 2 cylinder. Put a chunk of clear tubing instead of black, and what do you know I could see that the petcock is the problem, leaking gas into number 2 cylinder while the bike was turned off. Changed the petcock and problem solved. Now I am going to have to flip a coin for the next couple of days to see which bike to ride.

Thank you again to everyone who contributes their time and energy to this site. I will be hangin' around here a lot.

[Fishman]

With 5 GS's, you're bound to have something useful to contribute yourself. Welcome aboard.

[850 Combat]

What do you mean by "taking spark"? It is sparking but not firing?

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850combat
What I meant was everything seemed in order except I could not get a spark plug to fire. Different plugs no different. I changed out almost all of the electrical service except the main wiring harness; coils, wires, plugs, ignitor, rectifier, pickup coils, and still no spark. Like Reddirtrider suggested, I checked the wires feeding the coil, and traced the problem back to a faulty connection inside the headlight housing. It is a green plastic connection with 3 wires 2 of them supply power to the coils, and one had corroded (orange/white stripe). It should have been one of the first things I checked, but simple things often elude me.