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I am completly stuck and cannot even comtemplate any more possible answers. I need some fresh ideas guys, please...

ok I have a '80 cx500 c. I just finished doing a complete resto using most of the original parts. I had a slew of problems i have worked out and now im down to my last one. my left cylinder is not running at idle. once i get up to about 3k rpm it kicks in and the bike goes, but i cannot get it to run at idle unless i kick the idle up to about 3krpm. I've put on new coils and wires. tuned the **** out of the carbs. checked for vacum leaks (as far as i can tell i dont have any more) checked compression (about 135 on both cylinders) tried to check timing (didnt work out too well) swapped plugs. pulled apart the carbs to synchronise them by eye. (butterflys opening evenly)
i did have some problems with the cut off valve... first was a vacuum leak coming from the cover, fixd that and next was the diaphram was stuck in. so i pulled it out, cleaned it up and it seems to move freely now. i also made sure the little vacuum port was clear so it could pull the diaphram properly. and i did check the vacuum by sticking my finger over it while running. everything seems to check out. should i check anything else in there ?

now the reason the timing check didnt work out very well is because when i pulled the plug out to check for the slashes it kept throwing oil all over my light. and that light is too expensive to be ruined checking something that the book says probably isnt the problem anyway. the other reason the timing didnt work out, was i couldnt idle the bike at 1100 because my tach recently broke and i havnt found the part to fix it yet, so i would have to guess where 1100 is...

so i need some real help. thanks in advance to anyone with any suggestions. !!!

scorpion wrote:I am completly stuck and cannot even comtemplate any more possible answers. I need some fresh ideas guys, please...

ok I have a '80 cx500 c. I just finished doing a complete resto using most of the original parts. I had a slew of problems i have worked out and now im down to my last one. my left cylinder is not running at idle. once i get up to about 3k rpm it kicks in and the bike goes, but i cannot get it to run at idle unless i kick the idle up to about 3krpm. I've put on new coils and wires. tuned the **** out of the carbs. checked for vacum leaks (as far as i can tell i dont have any more) checked compression (about 135 on both cylinders) tried to check timing (didnt work out too well) swapped plugs. pulled apart the carbs to synchronise them by eye. (butterflys opening evenly)
i did have some problems with the cut off valve... first was a vacuum leak coming from the cover, fixd that and next was the diaphram was stuck in. so i pulled it out, cleaned it up and it seems to move freely now. i also made sure the little vacuum port was clear so it could pull the diaphram properly. and i did check the vacuum by sticking my finger over it while running. everything seems to check out. should i check anything else in there ?

now the reason the timing check didnt work out very well is because when i pulled the plug out to check for the slashes it kept throwing oil all over my light. and that light is too expensive to be ruined checking something that the book says probably isnt the problem anyway. the other reason the timing didnt work out, was i couldnt idle the bike at 1100 because my tach recently broke and i havnt found the part to fix it yet, so i would have to guess where 1100 is...

so i need some real help. thanks in advance to anyone with any suggestions. !!!

Sounds like a plugged/fouled pilot jet in the carb to me....usually what low idle problems stem from in my experience...

Good luck figuring it out man

One day several weeks ago my 1978 cx500 decided not to fire so I bid and won a replacement ignition control module. It runs now but exibits the exact same symtoms as your bike. It fires at a dead idle , the left cylinder drops off till around 3000-3500 rpm (hang on) and doesnt miss a beat to redline. I too have switched and substituted plugs and coils, inspected and blown out jets. Will give the carbs one more going over but suspect posibly a coil trigger,mounted of course on the back side of the engine accessable only after removing said engine. Will post my results/findings. Chuckey

take a squirt can with some gas in it and squirt it in the carb while it is idling if it starts hitting then you know it is the carburetor.pulling the engine sucks.

There's a complete '78 CX500 engine sitting in my garage, so if you need something off it gimme a holler!

Chuckey here, got a tip from some buddies in the Netherlands they suggested I check the resistance in the sparkplug caps. It should be right around five thousand ohms. Much more and the coils cant fire through till the RPMs are up.If the caps check out, cut about an eighth of an inch of insulation off each coil wire and screw the caps back on snugly. I fixed mine. Let me know how it works out , Chuckey