Stumble/Misfires 6K-8K Can't Find Source - Kawasaki Ninja 250R Forum
 
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post #1 of 5 (permalink) Old 06-20-2014, 07:33 PM Thread Starter
EIF
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Location: Champlain Valley
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Stumble/Misfires 6K-8K Can't Find Source

Greetings! I'm on my 2nd EX250, a basement find that had been idle for 15 years, and I'm stumped on how to deal with a bad stumble from 6K to 8K.

1992 model
unipod filter in unmodified airbox
F1 slipons
New battery
stock jets, 1 washer shim, air/fuel screws dialed out 3.25 turns
swapped out four coils & two CDIs, mix and match did not make a difference - all second hand parts

Bike idles fine, have made adjustments and tweaks to idle, no difference. Up to 5K revs fine, if I never had to break 40mph I would not even notice. Over 8K the bike pulls fine again to 11K, which is as high as I dared go.

Carbs were a brick when I got the bike. They have been rebuilt twice and in and out four times.

No apparent damaged to wiring. All other electrical works fine.

Help!
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post #2 of 5 (permalink) Old 06-21-2014, 06:08 AM
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Quote:
Originally Posted by EIF View Post
....I'm stumped on how to deal with a bad stumble from 6K to 8K.

unipod filter in unmodified airbox
F1 slipons
stock jets, 1 washer shim, air/fuel screws dialed out 3.25 turns
You are too lean for the range

Either add another washer, go up a jet size and set the pilot screws @ 2.5 turns (no more than 3), if you have to go more than 3 turns for the best results, increase the pilot jet 1 size up
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post #3 of 5 (permalink) Old 06-22-2014, 04:08 PM Thread Starter
EIF
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Went to three washers on the needles, air/fuel at 2.5 turns. Stumble from 6K to 8K worse than before. Still pulls fine from idle to 5K, then 9K to 11K.

Thinking I need to go to 112 jets and the next size up pilot jet.
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post #4 of 5 (permalink) Old 06-23-2014, 08:40 AM
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Quote:
Originally Posted by EIF View Post
....Thinking I need to go to 112 jets and the next size up pilot jet.
With a stock airbox and slip on, 112 mains may be too big. Stock main jets are
#105.

How are the pods filters fitted in the stock airbox? Post pics.

Last edited by DaBlue1; 06-23-2014 at 08:57 AM.
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post #5 of 5 (permalink) Old 06-24-2014, 06:31 PM Thread Starter
EIF
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Quote:
Originally Posted by DaBlue1 View Post
With a stock airbox and slip on, 112 mains may be too big. Stock main jets are
#105.

How are the pods filters fitted in the stock airbox? Post pics.
I ended up ordering 110 & 38 jets. Should be here Thursday. New plugs will be here Friday, might as well have fresh ones to assess the rejet.

I have a uni brand foam air filter in the stock box, my mistake in the description.
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