Idle problem

cgborders · May 16th, 2012, 04:39 PM

So I'm going to assume I have a vacuum leak, but feel free to tell me if I'm wrong.

Getting a '93 250 back on the road with about 4K miles on the clock. Bike has been sitting for a few years. Cleaned carbs, new oil/filter, plugs. The bike started right up and revs/ runs out very well. The problem is at idle. If I rev it it settles back to around 3k, very smooth. The periodically it starts to drop and if I let it it will die. Few revs and it will settle back to 3k.
It does respond at any point to the idle adjuster.
I've tried spraying all vacuum areas with WD40 and ether- nothing changed anywhere.
Carb boots are soft. clamps were maxed so switched to hose clamps.

Any ideas/ recommendations as to where to go next?

alex.s · May 16th, 2012, 05:12 PM

sounds like the idle air mix screws are set too lean. try turning them in a turn or two.

cgborders · May 17th, 2012, 01:48 PM

Ok, think I made some progress- now looks more electric. I'm loosing a coils. Its was idling fast (very smooth) then just dropped. I unplugged the left coil and nothing changed (absolutely nothing), hooked back up. Unplugged right and bike died instantly.
So sounds like something is wrong (intermittently) with left cylinder electronics.

cgborders · May 17th, 2012, 02:58 PM

Well I have power to coil, and looks like I have a good spark. I checked the plugs and gaped incorrectly so replaced with a good set and gaped. No difference.
Back to thinking fuel- if I spray ether directly into left carb it does rev up. And if i rev it it will run fine (if it was electric don't think it would respond to throttle changes).
I messed with idle mix screw and it did not seem to make any difference.

Any thoughts as to what might cause idle circuit to work intermittently?

alex.s · May 19th, 2012, 12:58 PM

sync the carb throttles

it sounds like its closing the throttle too much on the cylinder that stops firing

May 16th, 2012, 04:39 PM	#1
cgborders ninjette.org member Name: Chris Location: Knoxville Tennessee Join Date: Feb 2012 Motorcycle(s): Road star bagger, KZ400 bobber, kz305 cafe racer, '94 ninja 250 cafe project, vfr750 Posts: 17	Idle problem So I'm going to assume I have a vacuum leak, but feel free to tell me if I'm wrong. Getting a '93 250 back on the road with about 4K miles on the clock. Bike has been sitting for a few years. Cleaned carbs, new oil/filter, plugs. The bike started right up and revs/ runs out very well. The problem is at idle. If I rev it it settles back to around 3k, very smooth. The periodically it starts to drop and if I let it it will die. Few revs and it will settle back to 3k. It does respond at any point to the idle adjuster. I've tried spraying all vacuum areas with WD40 and ether- nothing changed anywhere. Carb boots are soft. clamps were maxed so switched to hose clamps. Any ideas/ recommendations as to where to go next?

May 16th, 2012, 05:12 PM	#2
alex.s wat Name: wat Location: tustin/long beach Join Date: Sep 2009 Motorcycle(s): wat Posts: Too much. Blog Entries: 5 MOTM - Oct '12, Feb '14	sounds like the idle air mix screws are set too lean. try turning them in a turn or two. __________________________________________________

May 19th, 2012, 12:58 PM	#5
alex.s wat Name: wat Location: tustin/long beach Join Date: Sep 2009 Motorcycle(s): wat Posts: Too much. Blog Entries: 5 MOTM - Oct '12, Feb '14	sync the carb throttles it sounds like its closing the throttle too much on the cylinder that stops firing __________________________________________________

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May 17th, 2012, 01:48 PM	#3
cgborders ninjette.org member Name: Chris Location: Knoxville Tennessee Join Date: Feb 2012 Motorcycle(s): Road star bagger, KZ400 bobber, kz305 cafe racer, '94 ninja 250 cafe project, vfr750 Posts: 17	Ok, think I made some progress- now looks more electric. I'm loosing a coils. Its was idling fast (very smooth) then just dropped. I unplugged the left coil and nothing changed (absolutely nothing), hooked back up. Unplugged right and bike died instantly. So sounds like something is wrong (intermittently) with left cylinder electronics.

May 17th, 2012, 02:58 PM	#4
cgborders ninjette.org member Name: Chris Location: Knoxville Tennessee Join Date: Feb 2012 Motorcycle(s): Road star bagger, KZ400 bobber, kz305 cafe racer, '94 ninja 250 cafe project, vfr750 Posts: 17	Well I have power to coil, and looks like I have a good spark. I checked the plugs and gaped incorrectly so replaced with a good set and gaped. No difference. Back to thinking fuel- if I spray ether directly into left carb it does rev up. And if i rev it it will run fine (if it was electric don't think it would respond to throttle changes). I messed with idle mix screw and it did not seem to make any difference. Any thoughts as to what might cause idle circuit to work intermittently?