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idling on one cylinder

5K views 44 replies 11 participants last post by  Johnny Gaijin 
#1 ·
my bike (a '75 cl360) has been idling on one clylinder and i suspected it was the coil or spark plug wire. so i replaced the coil and plug and i've got good spark but still it won't idle on that cylinder. the bike runs fine, both cylinders work when i'm moving but at idle... any suggestions would be mucho appreciated. type slowly because i'm mechanically retarded.

thanks!
 
#2 ·
You are probably looking at a fuel delivery issue or a vacume leak. Start the bike and idle it, use a squirt bottle to squirt water near the carb boots where they join the head and carb, spray on the carb as well. See if this causes the bike to run any diffrently, If it does you have a vacume leak. If it is a fuel delivery problem you could try adjusting your carbs or take them apart and clean them out.

Hey someone pas me the wrench........ Ahh screw it where is the torch
 
#3 ·
You are probably looking at a fuel delivery issue or a vacume leak. Start the bike and idle it, use a squirt bottle to squirt water near the carb boots where they join the head and carb, spray on the carb as well. See if this causes the bike to run any diffrently, If it does you have a vacume leak. If it is a fuel delivery problem you could try adjusting your carbs or take them apart and clean them out.

Hey someone pas me the wrench........ Ahh screw it where is the torch
 
#4 ·
sprayed water on the carb to no effect.
adjusting the air mixture screw has zero effect. (since i can't really adjust it where should it be approximately? i've got it at 2.5 rotations out is that anywhere close to where it should be?)
i removed and cleaned out my carbs about nine or ten months ago, do they gum up that fast?
 
#5 ·
sprayed water on the carb to no effect.
adjusting the air mixture screw has zero effect. (since i can't really adjust it where should it be approximately? i've got it at 2.5 rotations out is that anywhere close to where it should be?)
i removed and cleaned out my carbs about nine or ten months ago, do they gum up that fast?
 
#6 ·
sounds to me like a clogged pilot jet or pilot air passage but i'm no cb wizz. these passages are what feed air into your engine with a closed throttle with enough velocity to atomize the fuel. the mixture exits in front of the needle jet. the holes are so small that many people don't even realize they are there to begin with. use carb cleaner and carefully wiggle one strand of a copper wire to dislodge the **** (wire brush steel wire or ss safety wire is too big and steel being harder than aluminium will likely damage the shape/size of the hole). blow BACKWARDS with compressed air only if you need to. i like to use the carb cleaner (with straw ) to back blow the passage (the straw pointing down through the top of the carb with the slide removed). use a bright light and a lupe (magnifying lens) to confirm there are no blockages (shine down through the top and look into the back of the carb into the little holes). the pilot jet is easy to to remove, clean, inspect (as above), and re-install. hope this helps...please let us know how you're doing.
parks
ps if you can switch carbs easily and the faulty cylinder switches sides, you know it's a carb problem and not an ignition problem...the bad side will display a wet plug after a minute or two of idling on one cylinder.
 
#7 ·
sounds to me like a clogged pilot jet or pilot air passage but i'm no cb wizz. these passages are what feed air into your engine with a closed throttle with enough velocity to atomize the fuel. the mixture exits in front of the needle jet. the holes are so small that many people don't even realize they are there to begin with. use carb cleaner and carefully wiggle one strand of a copper wire to dislodge the **** (wire brush steel wire or ss safety wire is too big and steel being harder than aluminium will likely damage the shape/size of the hole). blow BACKWARDS with compressed air only if you need to. i like to use the carb cleaner (with straw ) to back blow the passage (the straw pointing down through the top of the carb with the slide removed). use a bright light and a lupe (magnifying lens) to confirm there are no blockages (shine down through the top and look into the back of the carb into the little holes). the pilot jet is easy to to remove, clean, inspect (as above), and re-install. hope this helps...please let us know how you're doing.
parks
ps if you can switch carbs easily and the faulty cylinder switches sides, you know it's a carb problem and not an ignition problem...the bad side will display a wet plug after a minute or two of idling on one cylinder.
 
#10 ·
secondary jet clog. dont spray your carb area with water. use wd40. if it picks up in speed, you have a leak. wd good. water bad.


really, all the fast guys are starting to hang out here. i might have to leave.



jc

aaron sent my wheel!
 
#11 ·
secondary jet clog. dont spray your carb area with water. use wd40. if it picks up in speed, you have a leak. wd good. water bad.


really, all the fast guys are starting to hang out here. i might have to leave.



jc

aaron sent my wheel!
 
#12 ·
If after doing everything parks61 says, it still won't idle then check that the idle speed screw isn't backed all the way out. You need the butter fly open just a little for them to idle. I'd check it before doing what parks61 said but you could do it after too, you'll learn a lot about taking the carbs apart if you do it that way.

Mike O.
 
#13 ·
If after doing everything parks61 says, it still won't idle then check that the idle speed screw isn't backed all the way out. You need the butter fly open just a little for them to idle. I'd check it before doing what parks61 said but you could do it after too, you'll learn a lot about taking the carbs apart if you do it that way.

Mike O.
 
#20 ·
secondary jet clog indeed. the first time i removed and cleaned my carbs it took me two weeks to figure it out. this time it took three hours to remove, clean, and re-install. that's progress.

this forum is awesome, i'd be out hundreds of dollars in mechanic's fees if it weren't for you guys.

THANKS!
 
#23 ·
ARGH. so after i cleaned the carbs it was idling on both cylinders (although definately favoring the one that was working before) for about a week and then poof my bike dies at a stoplight and now only idles on one clyinder again. i cleaned the carbs again and still nothing. i switched the plugs and nothing. i'm definately getting spark but no love at all from that cylinder.

help!
 
#26 ·
quote:
is there some kind of poor man's compression test i can do? i don't have much in the way of tools...
you can do a leakdown test, will tell you if the rings are holding at all. With the suspect cylinder at top dead center remove the spark plug and using a old plug (with the center knocked out) pressurize the cylinder to 5 psi and hold it. see how long it takes for the pressure to leak out. It should not be instantaneous but rather take a couple of seconds.

However, I am still leaning toward it being carb related. How clean is your tank and how old is the gas in it. That tank inside should be spotless. If cleaning the carbs caused the problem to go away then I would continue to follow that logic. It sounds to me like a clogged idle circuit and you have dirty fuel. Also check for kinks in the line leading to that carb, sometimes the vacuum can pull fuel through where it would otherwise not flow.
 
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