idle problem

[veeder]

I have a polaris 01 500 XC SP. whenever I start it up it will only run on one cylinder. when I get the rpm's up it runs on both cylinders and sounds great, it seems to me as if one of them is not getting enough fuel, not sure how to sync my carbs. or maybe its another problem. The carbs were just taken apart and cleaned this morning. any help would be great thanks

 

[2003Summit]

I have a polaris 01 500 XC SP. whenever I start it up it will only run on one cylinder. when I get the rpm's up it runs on both cylinders and sounds great, it seems to me as if one of them is not getting enough fuel, not sure how to sync my carbs. or maybe its another problem. The carbs were just taken apart and cleaned this morning. any help would be great thanks

Could be week spark, could be bad spark gap. Could be a fuel problem in the idle circuit of one carb. If it starts to run fine above 1/4 throttle, it's often a sign of a problem idle circuit. It it starts to run on it with a bit of choke, it's more a sign of the same.

If you let it miss for a minute and then pull both plugs, you can see which one is missing by the look of the plug (one will be white/tan and dry = working; the other will be dark and wet = not working). When you do this, let it miss for a while then kill it with the kill switch while it's still missing and let the throttle off as well if you are holding it down.

I would try new plugs first then take the carbs apart and carefully check them again. The smallest little dirt can plug and idle circuit. Did you use carb cleaner or just blow out? Some times there is varnish and you have to soak it for days - a week to get it out. Some times I use a fine little wire (like a strand of a bicycle brake cable) to poke through the holes and get stuff out. When you put the carbs back together, check the service manual for the starting setting for the fuel screws. A lot of products are 1-1/4 turns out but not all. You have to fine tune from there.

Why were the carbs taken out, how was it running before?

 

[veeder]

Could be week spark, could be bad spark gap. Could be a fuel problem in the idle circuit of one carb. If it starts to run fine above 1/4 throttle, it's often a sign of a problem idle circuit. It it starts to run on it with a bit of choke, it's more a sign of the same.

If you let it miss for a minute and then pull both plugs, you can see which one is missing by the look of the plug (one will be white/tan and dry = working; the other will be dark and wet = not working). When you do this, let it miss for a while then kill it with the kill switch while it's still missing and let the throttle off as well if you are holding it down.

I would try new plugs first then take the carbs apart and carefully check them again. The smallest little dirt can plug and idle circuit. Did you use carb cleaner or just blow out? Some times there is varnish and you have to soak it for days - a week to get it out. Some times I use a fine little wire (like a strand of a bicycle brake cable) to poke through the holes and get stuff out. When you put the carbs back together, check the service manual for the starting setting for the fuel screws. A lot of products are 1-1/4 turns out but not all. You have to fine tune from there.

Why were the carbs taken out, how was it running before?

I used carb cleaner to clean them out, jets and everything are clean, its definatly not a spark problem cause when I touch them to the cylinders I have great spark. when I give it some choke it runs on both cylinders.

the carbs were taken apart and cleaned because I rebuilt my top and bottom end.

 

[veeder]

could it be that maybe the idle screw is out on the one carb

 

[2003Summit]

could it be that maybe the idle screw is out on the one carb

Likely. It's either got dirt in it, it's damaged or it's set wrong, or it was assembled wrong. I would take em apart again and go through them (it) if all else fails. Find out which one is missing as I suggested, then you only have to go through one. Start with the easy stuff then work to hardest. Try the plugs and reset the idle screw on the problem side first. Take the idle screw out and examine it if it's damaged buy a new one. You can also try and blow some air into it and then put it back, bottom it (gently so you don't damage the seat), then back it out 1 and 1/4 turns, then go from there.

BTW the spark test you did doesn't mean much, other than it's making a spark. If the plug is bad, the wire is bad, or the gap is wrong, it can still make it miss at certain air mixture ratios (ie. different RPM/throttle) even though it makes a good spark as you tested it. I would also try at least some other plugs to be sure. Even a slight gap change can make them miss. These little engines can be fussy.

 

[2003Summit]

Hey, how long did you let them soak for? Were they fully immersed or parts sticking out of the fluid? Did you blow out all ports both ways? Then soak some more?