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Discussion Starter · #1 ·
Hi guys,



I've got a '79 CX500C. Carbs have been completely rebuilt, cleaned and bench balanced. I still need to vacuum sync them but before I do that I figured I'd ask about this minor issue I'm seeing.



The bike runs well, except for the fact that when it's cold, it will sometimes die while idling. Once warmed up there is no problem. I've checked for vacuum leaks and things look pretty good, jetting is running slightly rich but not enough to be a huge problem. So I guess my question is what I should look at next, before doing vacuum sync?



Thanks.
 

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Hi guys,



I've got a '79 CX500C. Carbs have been completely rebuilt, cleaned and bench balanced. I still need to vacuum sync them but before I do that I figured I'd ask about this minor issue I'm seeing.



The bike runs well, except for the fact that when it's cold, it will sometimes die while idling. Once warmed up there is no problem. I've checked for vacuum leaks and things look pretty good, jetting is running slightly rich but not enough to be a huge problem. So I guess my question is what I should look at next, before doing vacuum sync?



Thanks.
hi Faber,first can you update your signiture line,include your location and your bikes details.

can you just confirm,how you checked for vacumn air leaks.?



what idle are you showing at cold[when it dies]and hot when its fine?



how mant turns are you mixture screws out?

 

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faber



Are you using the choke during startup? The choke has a fast idle cam built into it so that the engine will run a bit faster with it on.



My CX will not run cold without choke.
 

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Discussion Starter · #4 ·
Hi guys,



I visually checked for cracks and leaks around both carb insulators as well as trying the `propane trick'. In neither case did I see or hear anything that would indicate air leaks.



The mixture adjustment screw is 2.5 turns out from zero. I'm running 85/130 mains with cone filters and mac 2 into 1 exhaust.



The bike does idle fine with the choke on and generally idles around ~1000 RPM's when warm, cold it's closer to 600 RPM's until it dies, It does struggle to keep running but will die without some choking or goosing of the throttle.
 

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Hi guys,



I visually checked for cracks and leaks around both carb insulators as well as trying the `propane trick'. In neither case did I see or hear anything that would indicate air leaks.



The mixture adjustment screw is 2.5 turns out from zero. I'm running 85/130 mains with cone filters and mac 2 into 1 exhaust.



The bike does idle fine with the choke on and generally idles around ~1000 RPM's when warm, cold it's closer to 600 RPM's until it dies, It does struggle to keep running but will die without some choking or goosing of the throttle.




I would suggest using the choke. There is a reason why it's there. I push choke knob down once I get moving so I don't forget it.



Many older cars/trucks had manual chokes and were used during cold starts. With fuel injection nowdays people aren't used to using something with a choke.
 

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Or perhaps the choke fast idle mechanism needs adjustment.



I've just rebuilt a set of 650 carbs and the choke wasn't lifting the idle at all.
 

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Or perhaps the choke fast idle mechanism needs adjustment.



I've just rebuilt a set of 650 carbs and the choke wasn't lifting the idle at all.


One way to check this is to put your hand on the throttle. If pulling the choke knob up is easier while turning the throttle a bit then the fast idle will do something.
 

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I prefer to stick my finger in the throttle mechanism between the carbs and see if there's movement when the choke is pulled.
 

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Maybe given the bikes setup a 90 would be better but since it idles warm I'm thinking choke/throttle interface adjustment.
 

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Hi guys,







The bike does idle fine with the choke on and generally idles around ~1000 RPM's when warm, cold it's closer to 600 RPM's until it dies, It does struggle to keep running but will die without some choking or goosing of the throttle.
mmm,if that were my bike......go for a ride,getting everything up to temperature,back put it on the main stand,adjust your tick-over curdled [black]center nut to say...1200rpm[1100 is ideal,when everything is right]what does[the next day]bring your cold tickover up to.....

do not let your bike idle at 600rpm,the oil pump wont be operating correctly at that low an rpm
 

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Discussion Starter · #12 ·
Hi,



Thanks for the suggestions guys!
 
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