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Discussion Starter · #1 ·
I have a 1976 CB500T that has developed a short on the right cyliner. When I can get the bike to run (on 1 cylinder) there is no flash from my timing light from the right spark plug wire. The left side is ok. This problem came out of nowhere when I was in the process of restoring the bike. Since I was going to replace the entire ignition system I figured the problem would get fixed (I figured it would be a bad wire coming out of the coil). After new Dyna coils, new spark plug wires, new points, new condenser, battery, starter solenoid etc. the problem is still there. What's really weird is that the short comes and goes. Sometime the bike will run fine, then wham, the right cylinder goes dead. When the bike was running, I had a friend go back over the ignition timing. He declared everthing in order, point gap ok, plugs ok etc. The next day same problem back again. He swore it was a bad condenser so I located a brand new Honda condenser and put it on. Guess what, right side still dead. I'm at my wits end. The last thing I did was to check the continuity of all the wires going to the coils. They all checked out ok. My local repair shop just cleaned out the carbs and told me I was imagining things, there was nothing wrong with the spark. I rode the bike home and the next day the same problem surfaced. Has anyone run into this problem? If can just find this gremlin I'm back on the road. Thanks in advance for any help. Sorry for the long post but I figured all the relevant facts would help.

Keith
 

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keithpip said:
I have a 1976 CB500T that has developed a short on the right cyliner. When I can get the bike to run (on 1 cylinder) there is no flash from my timing light from the right spark plug wire. The left side is ok. This problem came out of nowhere when I was in the process of restoring the bike. Since I was going to replace the entire ignition system I figured the problem would get fixed (I figured it would be a bad wire coming out of the coil). After new Dyna coils, new spark plug wires, new points, new condenser, battery, starter solenoid etc. the problem is still there. What's really weird is that the short comes and goes. Sometime the bike will run fine, then wham, the right cylinder goes dead. When the bike was running, I had a friend go back over the ignition timing. He declared everthing in order, point gap ok, plugs ok etc. The next day same problem back again. He swore it was a bad condenser so I located a brand new Honda condenser and put it on. Guess what, right side still dead. I'm at my wits end. The last thing I did was to check the continuity of all the wires going to the coils. They all checked out ok. My local repair shop just cleaned out the carbs and told me I was imagining things, there was nothing wrong with the spark. I rode the bike home and the next day the same problem surfaced. Has anyone run into this problem? If can just find this gremlin I'm back on the road. Thanks in advance for any help. Sorry for the long post but I figured all the relevant facts would help.

Keith
It sounds like there is a bad connection somewhere in the ignition wiring. I could be something as simple as the wire that connects the points not being positioned correctly and shorting out the point cover or the case.

If you change your profile, read this link ( viewtopic.php?f=4&t=3797 ) and let us know where you live maybe there is someone in your area that would take a look at it for you. If you're near Austin, Tx I'd be glad to take a look at it.
 

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Discussion Starter · #3 ·
Thanks Mike. I'm in Birmingham Alabama. This has been a tough one.
 

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keithpip said:
Thanks Mike. I'm in Birmingham Alabama. This has been a tough one.
I'll be coming through B'Ham later this month around the 20th or so. If you're still having troubles, I'd be glad to stop by and take a look at it. I only have a few hours but maybe I can help.
 

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Discussion Starter · #5 ·
Any help would be greatly appreciated. I'll keep you posted on how it's going.

Keith
 

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Try running it in the dark, Sometimes you can see an arcing situation.
 

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Keith, I had a similar problem on my 450. I had finished the restoration that included kits in the carbs and new coils, plugs and plug wires. The bike had a miss on the right cylinder and eventually it got bad enough that it would miss at idle. Like you that allowed me to trace it to electrical on the right side. I was stumped because I had replaced most of the electrical stuff. I tried swapping the coils and condensers from side to side (my plug wires are long enough to allow the right coil wire to reach the left plug and vise-verse. I plugged the right side points into the left coil and the left points into the right coil. The miss was still on the right. At this point the only thing left was the points and the wires from the coils to the points. I examined the points very closely and could find no problem with them but I installed and new set of Honda points and the problem is solved. There is an intermittent short to ground in those points but for the life of me I can't see the cause. The bike has not run this good ever. Don't know if this will help or not but swapping the coils and condensers from side to side allowed me to find the fault pretty quickly.

These points looked perfect!!


 

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A very old and common 450 problem is the shorting of the point(s) to the point cover.
For some reason it's more common on the right point.
Try running without the point cover, if it clears up, that's your problem.....

Many time you may think you've solved it, when all you really did was move the point cover or wire slightly.
 

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I had the same problem on my 360. I had to make a couple extra gaskets for my points cover to bump it out a bit more, haven't had the problem since.
 

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Discussion Starter · #10 ·
Update: had a friend come over and he noticed when looking at the points that the right side wire was in direct contact with the "ears" of the point plate causing the points to short out. I thought I had put the fiber washers in the correct place but they weren't. I guess it took another pair of eyes to see my mistake. Anyway the bike runs. When you first start it up it runs on the left side only but after a few minutes the right side suddenly kicks in. My theory is that the right side carb is dumping too much gas in and it takes a few minutes to get it all burned off. The timing still needs to be tweaked but I think the big problem is solved. Thanks to all who responded. You're a great group of people! I'll post some pics when the project is completed. Thanks again.

Keith
 
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