66cc Engine Can't Idle?
- Thread starter gage77
- Start date
It could be one of many things but if your lucky you just need to adjust your idle screw and/or idle air screw. There are several threads on carb adjustment if you take the time to search. There should be a sticky in Intake & Exhaust. Start simple and work your way up if you haven't already. Its heard to diagnose engine problems over text even with a lot of info and you didn't give us much.
And if you really think its the kill switch disconnect it and see its another simple one to check.
And if you really think its the kill switch disconnect it and see its another simple one to check.
I just noticed that my bike can't just sit there and idle like bikes on videos ive seen on youtube, I always have to have my throttle going or it will die out, someone told me that the kill switch is an electrical vampire, I unplugged it all, and it still cant seem to idle.
OK, let me give you a quick run down on the CNS....
The CNS carb has 3 jets, the Main jet, the IDLE jet, and the Enrichment (choke) jet.
Most motors dont like to idle when the Enrichment jet is open. It is there to richen the mix a bit and coax the motor to start when it is cold, it also helps smooth out the way the motor runs before it is warmed up, but the motor doesn't like to idle with it on. So make sure the Enrichment (choke) cable isn't being pulled at all.
The Main jet provides most of the fuel past idle, but at idle the pilot or idle jet is having a lot of influence on how she runs. The idle jet has an extremely small opening and clogs easily. Since the gas tanks are usually full of crud, debris can sneak through and clog up that idle jet very easily, when this happens she wont want to idle. I suggest you use a good in-line fuel filter to prevent this, and also clean the carb paying close attention to the idle jet. I blew carb cleaner through all my jets one time and still had crappy idle, the spray didn't clean the idle jet out properly. I cleaned it again, this time poking a tiny wire through the idle jet and she came clean, the bike idles great now. (I stripped the plastic off a garbage bag tie and used the tiny wire to ream the idle jet, anything similar will work, but dont jam anything in there and get it stuck, if it dont fit easily dont force it) It is very important that you filter your fuel line and keep the idle jet clean.
I guess before we go pointing fingers at the idle jet we should ask how the motor runs besides the idle issue? Does it respond well through the whole throttle range? How does the spark plug look? (so you can tell if she is running rich/lean or just right). If the motor isn't running well in general that could cause idle issues as well...
Finally, your idle issues could be completely unrelated to your carb or how your motor is running. It could actually be a cabling issue believe it or not. If the cable routing isn't smooth (or you didnt put light weight oil down the cable housing before you assembled) they can bind and the tension on them can vary as you move the handlebars around. The result is the throttle and/or choke may be moving a bit and effect the idle, or the clutch cable could be letting the motor bite a bit more or less depending on the handlebar position, the varying drag from the motor can cause the motor to die off... I had a bit of an issue with that last year cause my cable routing was crap. This year I changed my handlebars and re-cabled everything. I improved the cable routing and added flexible lined noodles to both ends of the throttle cable and clutch cable, and the carb end of the choke cable. My bike idles rock solid this year, I can set it so low I can hardly tell its running sometimes, but she rarely dies on me. (When she does die it's usually because I forgot to turn the fuel valve back on). BTW, always turn your fuel valve off when not riding....
Consider what I have said here and examine your situation to see which part, if any, applies to your situation...
Post back if you have more details or questions and we will try to help further....
The CNS carb has 3 jets, the Main jet, the IDLE jet, and the Enrichment (choke) jet.
Most motors dont like to idle when the Enrichment jet is open. It is there to richen the mix a bit and coax the motor to start when it is cold, it also helps smooth out the way the motor runs before it is warmed up, but the motor doesn't like to idle with it on. So make sure the Enrichment (choke) cable isn't being pulled at all.
The Main jet provides most of the fuel past idle, but at idle the pilot or idle jet is having a lot of influence on how she runs. The idle jet has an extremely small opening and clogs easily. Since the gas tanks are usually full of crud, debris can sneak through and clog up that idle jet very easily, when this happens she wont want to idle. I suggest you use a good in-line fuel filter to prevent this, and also clean the carb paying close attention to the idle jet. I blew carb cleaner through all my jets one time and still had crappy idle, the spray didn't clean the idle jet out properly. I cleaned it again, this time poking a tiny wire through the idle jet and she came clean, the bike idles great now. (I stripped the plastic off a garbage bag tie and used the tiny wire to ream the idle jet, anything similar will work, but dont jam anything in there and get it stuck, if it dont fit easily dont force it) It is very important that you filter your fuel line and keep the idle jet clean.
I guess before we go pointing fingers at the idle jet we should ask how the motor runs besides the idle issue? Does it respond well through the whole throttle range? How does the spark plug look? (so you can tell if she is running rich/lean or just right). If the motor isn't running well in general that could cause idle issues as well...
Finally, your idle issues could be completely unrelated to your carb or how your motor is running. It could actually be a cabling issue believe it or not. If the cable routing isn't smooth (or you didnt put light weight oil down the cable housing before you assembled) they can bind and the tension on them can vary as you move the handlebars around. The result is the throttle and/or choke may be moving a bit and effect the idle, or the clutch cable could be letting the motor bite a bit more or less depending on the handlebar position, the varying drag from the motor can cause the motor to die off... I had a bit of an issue with that last year cause my cable routing was crap. This year I changed my handlebars and re-cabled everything. I improved the cable routing and added flexible lined noodles to both ends of the throttle cable and clutch cable, and the carb end of the choke cable. My bike idles rock solid this year, I can set it so low I can hardly tell its running sometimes, but she rarely dies on me. (When she does die it's usually because I forgot to turn the fuel valve back on). BTW, always turn your fuel valve off when not riding....
Consider what I have said here and examine your situation to see which part, if any, applies to your situation...
Post back if you have more details or questions and we will try to help further....
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The cable coming from the carb that isnt the throttle is the Enrichment cable, it goes to that old timing style bicycle shifter lever. Make sure that cable is slack, cause when that cable is pulled the enrichment jet (choke) is engaged.
On the cable adjustments. At both the throttle and the carb ends there are adjustments. Screw out the adjuster(s) to tension the cable, then thread down the locking nut to hold it in position...
Hmm, I kinda assumed he already did this, but it's not always wise to overlook the obvious...
That's going to be a lot of help, especially if he doesn't live near someone who "knows what's going on".
If you have the cns2 the link below is my carb, the idle screw is in the center of the carb the screw close to the air cleaner is the idle air mixture.
http://motorbicycling.com/album.php?albumid=259&pictureid=1450
http://motorbicycling.com/album.php?albumid=259&pictureid=1450
http://motorbicycling.com/attachment.php?attachmentid=36232&d=1305735422 If you have too much play in the cable you can adjust the fitting on top of the carb and the one at the grip. Maybe the picture above will help,the adjusted is under the rubber boot.
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I had to adjust both the throttle end and the carb end as far out as possible to get the slack out of the cable. Having lots of slack in the cable is convenient when your pulling off the slide, but I shortened my cable so it needed less adjustment to take up the slack.
Shortening the cable inst that tough. I used a soldering iron and some thin single strand wire (like telephone wire) to make a new ball end on the carb side of the cable. First pull the cable from the slide, then wrap the wire strand around the cable a few times and place it in the position where you want the new ball end. Now solder the wire in place leaving a ball of solder similar to the size of the original ball end and then trim off the original ball end.
Shortening the cable inst that tough. I used a soldering iron and some thin single strand wire (like telephone wire) to make a new ball end on the carb side of the cable. First pull the cable from the slide, then wrap the wire strand around the cable a few times and place it in the position where you want the new ball end. Now solder the wire in place leaving a ball of solder similar to the size of the original ball end and then trim off the original ball end.
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Hard to give EXACT advice over the internet without being there to see what is really going on, or even seeing pictures...
That said, the throttle cables tend to be a bit slack, in most cases running the adjustment screw out all the way on BOTH the carb and throttle is enough to tighten it up. If you adjust both all the way out and there is still slack then you probably need to shorten the cable (after you have very carefully inspected everything in the throttle and are SURE you have it assembled properly).
I replaced the plastic throttle with a metal unit so I had no choice, I had to custom make the throttle cable. Since then I have changed my handlebars to a much taller profile and have had to re-cable again, second time around it was even easier and worked out perfectly for me.
Just to get a feel for what you are working with, pull the throttle off and expose the bare cable end. Pull the cable a few times and note the range of action, resistance etc. Now remove the two screws from the top of the carb where the cables go in. Pull out the slide and choke plunger, pull the cable again and note the movement of the slide, make sure there is nothing preventing it from moving fully. Do the same with the choke plunger making sure that one fully returns to closed (slack position). When putting the assembly back together note the long slot on the slide and align it with the peg that is inside the carb, a little twist back and forth and it will find its place and slide back down into the carb. Inspect and reinstall the throttle. Now that you are fully familiar with the mechanism, you tell me if you need to shorten the cable or not?
