QuestionPlease help with probs 81 cx500 will not run in the rain. Took carbs aprt. clean as a whistle. check timing. Right on. sprayed coiols and cdi, etc with water seems ok. located vaccuum leak and repaired. do not want to buy new coils and cdi if they do not fix it. also get some back fire while throttle is coming down with a load on engine. is there something common i can check? how can i check coils or cdi without buying new? tried 3 sets of coils these are the best i have. all used. it will in the rain but as soon as i get like up to 20 mph, it fails. any info on this will be greatlt appreciated.
AnswerIf spraying water on the coils didn't make it falter or die they are not likely to be the problem, but it sounds like an electrical problem to me.
First, check the spark plug wells in the cylinder heads to make sure they aren't filling up with water. There are plug well drain holes visible on the outside sides of the heads about half way between the block and the rocker cover and they must not be allowed to become blocked or the plug wells will fill up with water, which gets into the spark plug caps and shorts the spark. A fellow on one of the usergroups with similar symptoms found that the drains had been tapped and bolts put into them by a previous owner - when he removed the bolts the problem went away.
You should also take the plug caps apart and make sure the parts & connections inside them are clean and in good condition. Many have replaced the resistors inside the caps with similar length pieces of brass rod. If the springs are in bad condition they can usually be replaced with ball point pen springs. Unfortunately replacement caps are no longer available from Honda or NGK and the internal parts were never available individually. When you re-assemble the caps apply a small amount of automotive silicone art the joint between the rubber boots and the cap and the joint between the boot and the spark plug wire to help keep water from getting between them.
If the problem persists it could be the plug wires themselves - they are 27 years old, after all and even the best high silicone rubber insulation will deteriorate after that many years. Try misting the wires with a pump spray while the engine is running - if it falters or dies you need new plug wires. The spark plug wires on CX500s with CDI were not designed to be replaceable.
There are three possibilities to fix this:
- Replacement coils are available through the aftermarket. Make sure you get the right ones for the CX500 with CDI because the ones for GL500, GL6650, CX650 and some late CX500s ('83 custom I think) with transistorised ignitors can do harm to the CDI circuitry.
- NGK makes spark plug wire joiners. If you are careful you could cut the old wires off short and use joiners to attach new wire to the caps. Caution - make sure there is somewhere for the joiners to fit before you cut the old wires. You could also coat the remaining part of the old wires with varnish or automotive silicone to help keep them dry.
- It is possible to cut away some of the casing and the old wire and attach new wire to the old coil. http://www.xs11.com/forum/showthread.php?s=&threadid=137
Re the afterfire: (Backfire comes from the carbs, afterfire from the exhaust.) This is not uncommon. It is usually caused by either leaks in the exhaust system or failing air cutoff valves. I recommend carb kits from www.randakks.com They are a bit more expensive than some, but they are the best carb kits for these bikes available. You might be able to find a better price at an online auction but you won't find better service or quality.
You should also consider joining an online usergroup (discussion forum) that specializes in this family of bikes such as http://choppercharles.com/cs/forums/
