idle issues

[jgcable]

could all these problems be with the suggested 2.5 turns out on the mixture screws?. When i drilled my caps off the factory setting was about 1/2 a turn out. When i checked my plugs on my totally stock bike set at 2.5 turns out they showed the bike running very rich. My last bike still had the caps on the carbs and it ran perfect with the plugs being a perfect tan color.

[csmith12]

Is this a new issue or related to your other thread (freshin' up)?

Is it worse when the bike is cold or hot?
Does the bike being wet make it worse (riding in the wet or after a wash)?
Is the jetting stock? Idle and mains?

Here is what I would do next.
Check the coils for any discolorations, maybe one or both are getting weak. You can ohm test them.
Check every inch of the spark plug wires.
Check the airbox, boots and intake boots for hairline cracks or other leaks.
Take the carbs out again and check; diaphragms and slides. Diaphragms for tiny holes and slides for good smooth operation, check inside the carb where the slides go as well. Maybe there is a deposit or something to prevent sliding all the way back down. (could be heat related here)

What you have going on is something that is hard to diag but can be found by thinking outside the box a bit.

[jgcable]

Originally Posted by csmith12

Is this a new issue or related to your other thread (freshin' up)?

Is it worse when the bike is cold or hot?
Does the bike being wet make it worse (riding in the wet or after a wash)?
Is the jetting stock? Idle and mains?

Here is what I would do next.
Check the coils for any discolorations, maybe one or both are getting weak. You can ohm test them.
Check every inch of the spark plug wires.
Check the airbox, boots and intake boots for hairline cracks or other leaks.
Take the carbs out again and check; diaphragms and slides. Diaphragms for tiny holes and slides for good smooth operation, check inside the carb where the slides go as well. Maybe there is a deposit or something to prevent sliding all the way back down. (could be heat related here)


What you have going on is something that is hard to diag but can be found by thinking outside the box a bit.

Is it worse when the bike is cold or hot? Temperature doesn't matter.

Does the bike being wet make it worse (riding in the wet or after a wash)? No

Is the jetting stock? Idle and mains? Totally Stock.


Check the coils for any discolorations, maybe one or both are getting weak. You can ohm test them. Tested and in perfect condition.

Check every inch of the spark plug wires. Perfect condition.

Check the airbox, boots and intake boots for hairline cracks or other leaks. No cracks or leaks. All boots are in new condition. There are no vacuum leaks of any kind.

Take the carbs out again and check; diaphragms and slides. Diaphragms for tiny holes and slides for good smooth operation, check inside the carb where the slides go as well. Maybe there is a deposit or something to prevent sliding all the way back down. (could be heat related here). Carbs were removed and cleaned 3 times. Twice by me and once sent out and sonic bathed. Slides are smooth. No deposits of any kind. When I manually move the slides up and down they both feel exactly the same. They are very smooth but there is a spot in each of them when they are lifted that there is a little resistance. Its the same spot on both carbs. I am pretty sure that's normal.

Throttle response on my bike is excellent. It pulls hard from 900 rpms all the way up to 12,000. No hesitation or bucking of any kind. No stumble. The throttle is very crisp. Its almost like its fuel injected. The ONLY problem is the return to idle. This morning the idle was at 2000 rpms for the entire hour ride to work. Then.. suddenly I came to a stop and the idle dropped to 900 and then stalled. I restarted and it stalled again. I restarted and it settled back into the 2000 rpms. I turned the idle down to 1500. It sat at 1500 perfectly for at least 15 minutes of riding. That's about 10 different full stops. Then... it decided to idle down to 900 rpms and almost stalled. I blipped the throttle before it stalled and it sat at 2000 rpms steady for the remainder of the ride. It never went back down to the 1500 rpms until I got to work and was sitting in the parking lot idling for a few minutes.

[csmith12]

Well crap dude, lets continue to think outside the box.

Your idle goal should be somewhere between 1200 and 1600ish. 900 is a bit low for a 250.
How is your exhaust? Headers tight and sealed? Any exhaust leaks, holes or clogs?
Defairing the bike and inspect the plugs and wires to the electrical components. Sometimes on my 4wheelers, I have to unplug and replug the connectors from vibration, dirt and other muck.
Unplug or pull the fuse to everything that is not required for the bike to run, plug them back in one at a time to isolate a problem in that area.
Any chance of getting a set of carbs to test with? How about getting another ecu to test with?
Where is your ecu mounted? Has it been moved?
Take the bike down a gravel road a few times. Does the bumps make it worse?
How bout the choke? Does it seem to be working as it should? I know you said you don't need the choke to start and run, but what happens when you turn it on?
You must keep your bike on a battery tender right? Leave it off for some time, does your battery go dead? What is the running voltage vs. voltage while the bike is off.
Check/clean the main ground of the wiring harness.
What color is the spark? White or blue?
Wiggle the spark plug wires while the bike is idling. Use a stick or something, not your hand.

[jkv45]

Turn the idle mixture screws in from the current 2.5 - .5 turn at a time.

Set the idle to 1300 hot.

Drain the floatbowls and look at what comes out - anything odd?

Check for vacuum leaks.

If the fuel in the floatbowls is anything but perfect, remove the tank and drain it, then refill with fresh 87 octane (ethanol-free if poss, or the lowest octane you can get without ethanol).

Add 1oz per gal of Chevron Techron Concentrate fuel system cleaner.

Report back...

[agentbad]

Make sure you turned them all the way in then turn them two 360's and one 180 out.

[jgcable]

Originally Posted by jkv45

Turn the idle mixture screws in from the current 2.5 - .5 turn at a time.

Set the idle to 1300 hot.

Drain the floatbowls and look at what comes out - anything odd?

Check for vacuum leaks.

If the fuel in the floatbowls is anything but perfect, remove the tank and drain it, then refill with fresh 87 octane (ethanol-free if poss, or the lowest octane you can get without ethanol).

Add 1oz per gal of Chevron Techron Concentrate fuel system cleaner.

Report back...

Turn the idle mixture screws in from the current 2.5 - .5 turn at a time. I have been doing that. I started at 2.5, went to 2 and I am now down to 1.75 turns in. No change at all.

Set the idle to 1300 hot. I set it at 1300 but after setting it and taking off for a ride it still will sit at either 900 and pick back up to 1300 or it will sit at 2000 steady or it will sit at 900 and stall.

Drain the floatbowls and look at what comes out - anything odd? Fuel bowls look perfect. The fuel that came out of them is perfectly clean.

Check for vacuum leaks. There are no vacuum leaks. I used carb cleaner and propane 2 different times.

If the fuel in the floatbowls is anything but perfect, remove the tank and drain it, then refill with fresh 87 octane (ethanol-free if poss, or the lowest octane you can get without ethanol). Fuel looks spotlessly clean.

Add 1oz per gal of Chevron Techron Concentrate fuel system cleaner. I have been running Seafoam in it for the past 4 fill ups with no change.

[jgcable]

Originally Posted by csmith12

Well crap dude, lets continue to think outside the box.

Your idle goal should be somewhere between 1200 and 1600ish. 900 is a bit low for a 250.
How is your exhaust? Headers tight and sealed? Any exhaust leaks, holes or clogs?
Defairing the bike and inspect the plugs and wires to the electrical components. Sometimes on my 4wheelers, I have to unplug and replug the connectors from vibration, dirt and other muck.
Unplug or pull the fuse to everything that is not required for the bike to run, plug them back in one at a time to isolate a problem in that area.
Any chance of getting a set of carbs to test with? How about getting another ecu to test with?
Where is your ecu mounted? Has it been moved?
Take the bike down a gravel road a few times. Does the bumps make it worse?
How bout the choke? Does it seem to be working as it should? I know you said you don't need the choke to start and run, but what happens when you turn it on?
You must keep your bike on a battery tender right? Leave it off for some time, does your battery go dead? What is the running voltage vs. voltage while the bike is off.
Check/clean the main ground of the wiring harness.
What color is the spark? White or blue?
Wiggle the spark plug wires while the bike is idling. Use a stick or something, not your hand.

I always use a battery tender. Battery is 5 months old. When running its sitting at around 13.8 volts. Main grounds and wires are factory perfect. This bike looks brand new inside and out. Spark is bluish white. Bumps don't affect it at all. ECU is factory mounted and secure. Spark plug wires are secure and nothing changes when they are touched.
I don't need a choke to start it and it starts immediately and idles perfectly. If I do pull the choke lever the idle increases the more I pull it. If I pull the choke in and try to start it, it will start immediately but the RPM's are between 4k and 5k. As soon as I push the choke lever out the idle decreases to anywhere from 1300 to 2000 depending on the mood of the bike.

[jkv45]

Originally Posted by jgcable

Turn the idle mixture screws in from the current 2.5 - .5 turn at a time. I have been doing that. I started at 2.5, went to 2 and I am now down to 1.75 turns in. No change at all.

Set the idle to 1300 hot. I set it at 1300 but after setting it and taking off for a ride it still will sit at either 900 and pick back up to 1300 or it will sit at 2000 steady or it will sit at 900 and stall.

Drain the floatbowls and look at what comes out - anything odd? Fuel bowls look perfect. The fuel that came out of them is perfectly clean.

Check for vacuum leaks. There are no vacuum leaks. I used carb cleaner and propane 2 different times.

If the fuel in the floatbowls is anything but perfect, remove the tank and drain it, then refill with fresh 87 octane (ethanol-free if poss, or the lowest octane you can get without ethanol). Fuel looks spotlessly clean.

Add 1oz per gal of Chevron Techron Concentrate fuel system cleaner. I have been running Seafoam in it for the past 4 fill ups with no change.

Something is funky with the carbs then. Did you replace the Pilot Jets with new ones?

My suggestion would be to take the carbs down completely and go through them again...very carefully...

As we discussed in a different thread, I think there's an issue with the idle mixture circuit. Either the o-rings are damaged or in the wrong place or something else is wrong.

[jgcable]

Originally Posted by jkv45

Something is funky with the carbs then. Did you replace the Pilot Jets with new ones?

My suggestion would be to take the carbs down completely and go through them again...very carefully...

As we discussed in a different thread, I think there's an issue with the idle mixture circuit. Either the o-rings are damaged or in the wrong place or something else is wrong.

New idle jets and the o-ring, washer and spring is in perfect condition on each screw. I agree... its a carb issue. Just can't figure out what it is. Road it home tonight 1.5 hours of stop and go traffic on the highway. It didn't stall once. It would idle down to around 900 and then pick itself up immediately to 1300 which is where I set it this morning. Go figure.