Runs better on choke? Why?
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From: wilmington nc
Runs better on choke? Why?
Ok guys i'm baffled. I try not to post every problem i have with my bike on here so I can figure it out on my own... but this one i just dont understand.
So my carbs are clean, unrestricted airbox, fuel pump is good, new spark plugs, new fuel filter. Air filter has been cleaned (but not new).
I fiddle with the choke and idle screw to get the bike to start on choke. I find that if i keep the idle at about 1500 and gag the throttle, it hesitates and doesnt catch. If i keep the idle at 2500 and gag it, it catchs immediately and climbs in RPMS like its supposed to. As soon as i let off, it drops back to 2500 instantly. All this is with choke ON.
When the bike is started, and I try to take the choke OFF, i have to run my idle adjustment screw way in for it to keep running. Same scenario that it gags at 1500. At 2500, it jumps all around a couple hundred RPM. When i hit the throttle it will raise to the desired RPM, but it sounds very rumbly, when I hold it at say 5,000... its poppin and backfiring, and when I let off, it slowly makes it way back down to the desired idle.
What i really dont understand, is that why does it run like a champ with the choke ON, when the choke is allowing more fuel to the mixture, but it has a god-awful smell of unburnt gas out the tail pipe????
heres some vid i took of what its doing. is it normal for the rpms to drop so slowly like this?
http://www.youtube.com/watch?v=8HgfGCDQa9o
So my carbs are clean, unrestricted airbox, fuel pump is good, new spark plugs, new fuel filter. Air filter has been cleaned (but not new).
I fiddle with the choke and idle screw to get the bike to start on choke. I find that if i keep the idle at about 1500 and gag the throttle, it hesitates and doesnt catch. If i keep the idle at 2500 and gag it, it catchs immediately and climbs in RPMS like its supposed to. As soon as i let off, it drops back to 2500 instantly. All this is with choke ON.
When the bike is started, and I try to take the choke OFF, i have to run my idle adjustment screw way in for it to keep running. Same scenario that it gags at 1500. At 2500, it jumps all around a couple hundred RPM. When i hit the throttle it will raise to the desired RPM, but it sounds very rumbly, when I hold it at say 5,000... its poppin and backfiring, and when I let off, it slowly makes it way back down to the desired idle.
What i really dont understand, is that why does it run like a champ with the choke ON, when the choke is allowing more fuel to the mixture, but it has a god-awful smell of unburnt gas out the tail pipe????
heres some vid i took of what its doing. is it normal for the rpms to drop so slowly like this?
http://www.youtube.com/watch?v=8HgfGCDQa9o
Last edited by intiractive; Sep 21, 2009 at 03:02 PM.
Hey man, sorry I'm a flake on the AIM, if I'm online it usually means I'm busy :/
Open your bowl valves one at a time, and make sure fuel is flowing out of each. Go over each one of the hoses that connect to your carb unit, and make sure they are run properly. It's very easy to connect the hoses wrong, and certain configurations will still allow the bike to start, but run like crap. There's a diagram on the back of the airbox if you need it. When you cleaned the carbs, did you remember to clean out all the hoses, too?
If all that is good, I'm reaallllyyy suspecting a combustion problem, here, especially with the "rumbly" sound. Pull your plugs and see if any are fouled or wet. If they are fouled, note the color.
I'm thinking one or more of your cylinders (probably two) aren't firing. Cranking the fuel mixture up allows the two remaining cylinders to produce enough power to get the engine rolling, but the two dead are just spitting the uncombusted fuel out the exhaust valves, and it evenetually ignites in the exhaust manifold, which is what the popping sound is.
If two cylinders are misfiring, it's probably because you have a dead coil. Even if your plugs look ok, test your wires for spark.
Open your bowl valves one at a time, and make sure fuel is flowing out of each. Go over each one of the hoses that connect to your carb unit, and make sure they are run properly. It's very easy to connect the hoses wrong, and certain configurations will still allow the bike to start, but run like crap. There's a diagram on the back of the airbox if you need it. When you cleaned the carbs, did you remember to clean out all the hoses, too?
If all that is good, I'm reaallllyyy suspecting a combustion problem, here, especially with the "rumbly" sound. Pull your plugs and see if any are fouled or wet. If they are fouled, note the color.
I'm thinking one or more of your cylinders (probably two) aren't firing. Cranking the fuel mixture up allows the two remaining cylinders to produce enough power to get the engine rolling, but the two dead are just spitting the uncombusted fuel out the exhaust valves, and it evenetually ignites in the exhaust manifold, which is what the popping sound is.
If two cylinders are misfiring, it's probably because you have a dead coil. Even if your plugs look ok, test your wires for spark.
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