need help 250 ninja stumbles/dies with throttle - Kawasaki KLR 650 Forum
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post #1 of 9 Old 01-27-2020, 01:33 PM Thread Starter
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need help 250 ninja stumbles/dies with throttle

i have a tough nut to crack.
08 ninja 250
carbs totally rebuilt by carb shop
have tried multiple ignitors
was running sticks coils(ohmed ok)
put stock coils on(ohmed ok)
compression test passed
valve check recently done, rechecked clearances all good. changed plugs(one looks like it’s running rich) yes carbs are synced and pilots are set
intake boots look ok.
symptoms started with airbox on
still did it with no airbox.
tried multiple batteries
is it possible for a cam to be out of round that is causing this? running out of options. it will idle normal but any throttle and it wants to die.
looking at back of carbs, left carbs slide starts to flutter and blows back when throttle applied.
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post #2 of 9 Old 01-27-2020, 03:43 PM
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In PM's I have suggested float bowl air vent restriction and slide valve Diaphragms pinched. I know either can do this.

Mavericks video is on post 10 of this link, https://www.ninjette.org/forums/show...75#post1263075
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post #3 of 9 Old 01-27-2020, 04:06 PM Thread Starter
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gordon(ductiman) is on this thread. we are talking about how this happened. might be a clue in there. thanx for helping. i hate any bike to sit idle for months trying to find out why

https://www.ninjette.org/forums/show...4&postcount=13
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post #4 of 9 Old 01-27-2020, 04:08 PM Thread Starter
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that didn't work, go to post 13
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post #5 of 9 Old 01-27-2020, 04:46 PM
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Have you not yet had the diaphragms out today?

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post #6 of 9 Old 01-27-2020, 04:52 PM Thread Starter
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i haven't touched it in months. will start up tomorrow. as stated, carbs totally rebuilt and deep cleaned.(factory new)
i did take it apart and look around but everything looked good.
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post #7 of 9 Old 01-27-2020, 05:49 PM
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The slides flutter because the vacuum cleaner is not running at a high enough RPM.

Of course they will flutter at lower RPM. It is a pulsed Intake and only every other revolution at that.

The question is why do they Not Continue to smoothly Rise? When they do not smoothly rise, they act as Choke Plates, making the system too rich to run properly & spit back. IMO.

You could try 'JdgDredds' o-ring under the plastic diaphragm retainer to lean out the low speed transition. While doing that you may spot a tiny pinhole or wear-thru on one or both of the slide diaphragms.

The 2005-2007 carburated Brute Force 750s had a little raised 'bump' front & center of the diaphragm cavity. The bump was for a Phillips screw thread 'boss' to hold the cold start enrichener valves in. The diaphragms would rub thru on those little bumps. I had to relieve them with a Dremel burr, they were still a blind hole, I never touched threads with the Dremel burr.

I can see Phillips screws holding the enrichener Slide Rail on the Ninja carbs in the service manual.

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post #8 of 9 Old 01-27-2020, 06:06 PM Thread Starter
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Quote:
Originally Posted by pdwestman View Post
The slides flutter because the vacuum cleaner is not running at a high enough RPM. <img src="http://www.klrforum.com/images/smilies/icon_wink.gif" border="0" alt="" title="Wink" class="inlineimg" />

Of course they will flutter at lower RPM. It is a pulsed Intake and only every other revolution at that.

The question is why do they Not Continue to smoothly Rise? When they do not smoothly rise, they act as Choke Plates, making the system too rich to run properly & spit back. IMO.

You could try 'JdgDredds' o-ring under the plastic diaphragm retainer to lean out the low speed transition. While doing that you may spot a tiny pinhole or wear-thru on one or both of the slide diaphragms.

The 2005-2007 carburated Brute Force 750s had a little raised 'bump' front & center of the diaphragm cavity. The bump was for a Phillips screw thread 'boss' to hold the cold start enrichener valves in. The diaphragms would rub thru on those little bumps. I had to relieve them with a Dremel burr, they were still a blind hole, I never touched threads with the Dremel burr.

I can see Phillips screws holding the enrichener Slide Rail on the Ninja carbs in the service manual.
i only see the left carb doing the flutter plus some kind of fuel mist blowing back with throttle applied
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post #9 of 9 Old 02-05-2020, 01:47 PM Thread Starter
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carbs went back to carb shop. found nothing, complete tear down wet test. on a hunch will change out camshaft position sensor.
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