QuestionI have a 1981 Honda CX 500 that I use to get around town. The bike has been running fine up till a few weeks ago when it started missing really bad. I pulled the plugs and they were carbon fouled. I have bought new plugs and cleaned the air filter but still have the same problem. The battery is new, I bought it a week after this started happening hoping it might help which it didn't. I also took the carbs apart to see if anything looked plugged and I drained and replaced the fuel. I dont know too much about carbs so all I checked was to see if the jets were obstructed or if the floats were sticking. After putting in the new plugs the bike ran like normal for a half hour or so and then started to miss or backfire. I found out that pulling the choke in or out I could get the bike to stay alive long enough for me to get back to the garage. Also it seems to miss in the right side only or at least while idling.
Since it will run normally for a short time it seems like it would be a carb problem but I may be totally off.
Thanks for reading and any help would be great,
Peter
AnswerPeter, this is a tough one to accurately diagnose on the web, but I can give you a few clues, perhaps.
First, you need to get the compression checked and the valves adjusted so we know that there isn't any major mechanical issues clouding the picture.
If the carbs were clean and jets were all in place and unrestricted, I would check the manifolds for air leaks and carbs for proper synchronization.
Your fouled plugs may be a case of one side dropping spark output and then the other side trying to drag the bike along with wide open throttle.
My gut feeling is that it may be electrical. CX500s were notorius for having issues with the pulser coils and stator. These are expensive items from Honda, but there may be some help from www.electrexusa.com, depending on which part is defective. If the stator and pulser coils are okay, then you have to check the spark control module (s). From what I can see on the http://www.powersportspro.com/partsfish/ site, there are two different types of charging systems, one with and one without the pulser coils built in. The all in one setup looks like $500 item from Honda!
I would get two sets of plugs. One set to check spark with when the bike gets hot and one set to be left in to get the bike heated up. It sounds like a heat-related electricatl failure of some kind. You don't want to throw a lot of parts/money at this until you understand exactly where the failure is occurring.
The ignition is self-powered CDI, so once you get it turned over, the battery is not a factor in the ignition system performance. Get professional help or buy a factory shop manual at www.helminc.com or Ebay, perhaps.
http://groups.msn.com/AustralianHondaCX500CX650Register/links.msnw
Bill Silver
