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Old June 3rd, 2018, 07:09 PM   #1
DirtyMike
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Name: Kelly
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Exclamation [1987] Need help fixing Idle

Hello Everyone,

I recently picked a 1987 ninja 250. I cleaned the carbs and put in new seals, injectors, and synced them. I also replaced the petcock as it was leaking on the side. I also think the petcock was clogging since bike would run for 5-10 minutes then shut off and not start again. After sitting for 20 minutes the bike would run again.
I replaced the spark plugs (Put in CR7HSA, not CR8HSA). I tightened the throttle and choke cables.

Now, I am trying to get the bike to idle but it is being stubborn. It will idle at around 3000 but will not stay. By that I mean it idles for 20-30 seconds then sputters down to 0. If I try to set it any lower than 3000 it will not idle at all. I messed with the air mixture screw in both directions but did not get any results. Any suggestions?
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Old June 3rd, 2018, 07:49 PM   #2
Z1R rider
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Best bet is that the idle jets and or passages are not cleaned. I and 100 others have thought we cleaned the carbs, but the passages are so small as to be almost impossible to get clean without special equipment. I had mine off soooo many times before I got them cleaned, shooting carb cleaner into the holes is almost a waste of time, I finally got mine cleaned with an ultrasonic cleaner and fine copper wire. A member here does (or did) offer a carb cleaning service, goes by ducatiman.

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Old June 4th, 2018, 06:58 AM   #3
jkv45
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Quote:
Originally Posted by DirtyMike View Post
Hello Everyone,

I recently picked a 1987 ninja 250. I cleaned the carbs and put in new seals, injectors, and synced them. I also replaced the petcock as it was leaking on the side. I also think the petcock was clogging since bike would run for 5-10 minutes then shut off and not start again. After sitting for 20 minutes the bike would run again.
I replaced the spark plugs (Put in CR7HSA, not CR8HSA). I tightened the throttle and choke cables.

Now, I am trying to get the bike to idle but it is being stubborn. It will idle at around 3000 but will not stay. By that I mean it idles for 20-30 seconds then sputters down to 0. If I try to set it any lower than 3000 it will not idle at all. I messed with the air mixture screw in both directions but did not get any results. Any suggestions?
Carbs...carbs...carbs...

I would say they need to come off again and be gone through (as Z1R noted...).

There are lots of details that need to be addressed to get them to function properly. Diaphragms could also be damaged.

It also sounds like you may have a vacuum leak.

As you noted, you may have fuel-flow issues. Check the tank for rust, check the filter at the carb inlet, check for debris inside the floatbowls, check that your vacuum line to the petcock is not damaged and that the petcock will open with vacuum, check that you tank is venting properly.

Those plugs are hotter that stock, so I'd go back to the original heat range once it's running properly. You shouldn't need hotter plugs if everything is correct, but it's fine to get it running.
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Old June 4th, 2018, 07:13 AM   #4
Triple Jim
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You mentioned the petcock clogging at some point. If the gas tank is full of debris like silty rust particles, it could mess up a new petcock too. Have you thoroughly cleaned the tank and installed a pleated paper inline filter in the line from the petcock to the carbs? If not, problems may keep popping up.
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