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Discussion Starter · #1 ·
It is a carb issue!!!!

Bike starts and idles and runs fine around town plenty of power and never stalls. When I get on the freeway and ride around 70MPH the bike seems to pulse like the power is slightly fluctuating. I hope that makes sense. If I am on the freeway and roll on the gas the bike takes off like a bandit, but when holding the throttle stead it surges and just doesn't seem to be running as smooth as it should. I cleaned the carbs and rebuilt them completely. new air filter too. Can bad carb synchronization do this? Or what are your thoughts? it is a frustrating issue....


Let me know
 

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Are your carburetor settings the same? My '97 M900 with flat-slides acted much like yours does when I first installed them.

I subsequently learned that my Ducati's engine also required staggered carburetor jetting so that the rear be set differently from the front's--the rear cylinder jetted just a little richer over the front one--to compensate for the rear's cylinder's higher operating temperatures. After rejetting, the bike ran much better and the surging at highway speeds went away.

jD
 

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Discussion Starter · #3 ·
You know when I rebuilt the carbs I might have mixed up the jets. That is a good idea I Will remove the carbs and check it out sometime soon.
 

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When you say rebuilt, how much did you do ? The idle air circuit is very easily clogged and , strangely enough, if it isn’t clean from float bowl to venturi , the bike just won’t run right. Also, if you didn’t replace the emulsion tube and needle , they tend to wear in the 3-4000 rpm area causing surging and poor running. A tuning kit from FactoryPro is what I used.
 

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Discussion Starter · #5 ·
it was a total rebuild all the way down to removing jets needles and so on. I did replace the emulsion tubes and needles with the exact size. I also did clean all air passages very good I placed them in an ultrasonic cleaner and ran brushes through the holes.
 

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Test with adding/removing fuel via opening the airbox lid. This should tell you if the bike is lean or rich at the given position, know that new needle jets could be leaner than what you had so yes jetting may have changed some. Also keep in mind if you used other than marked Mikuni jets/parts you most likely did change jetting even if they are labeled the same number/letter size.
 

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Discussion Starter · #7 ·
Thank you for all of the information can someone supply me with a place to get OEM Mikuni rebuild and jet kits?

Thanks
 

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I’m not too sure you’re going to find OEM. Keysters has kits. Try to find some with needles and seats. New diaphragms aren’t included and are very expensive so hopefully yours are okay. Clean them in soap and water, no solvents. They warp.
 

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Mikuni parts are available from Ducati so talk to your dealer... yes you may have to explain what a carburetor is as they have not been used since the latest parts persons were created.
 
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