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Discussion Starter #1 (Edited)
I have been chasing my tail on this one for awhile and can't seem to figure it out. The bike idles fine and runs great when on the gas hard but when going from idle to WOT, it stumbles and seems to drop a cylinder or two before snapping out of it and coming back on and running strong again all the way to the rev limiter. Any ideas what this could be? I have tried most/all potential electrical/fuel issues coils, injectors, ecu, stator, plugs, harnesses, sensors, fpr, etc. Could it be a timing issue or valve clearance issue? Any help or thoughts are appreciated very much. Thank you
 

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Re: CBR 929 Stumbling in Mid Range, Runs Good on Top, seems to be dropping cylinders

Be take it to a dyno to diagnose that, could be expensive though
 

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Discussion Starter #3
Re: CBR 929 Stumbling in Mid Range, Runs Good on Top, seems to be dropping cylinders

Be take it to a dyno to diagnose that, could be expensive though
Dyno is my next step if no one has any ideas. Could a vacuum line issue cause this?
 

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Re: CBR 929 Stumbling in Mid Range, Runs Good on Top, seems to be dropping cylinders

Possibly the servo?
 

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Re: CBR 929 Stumbling in Mid Range, Runs Good on Top, seems to be dropping cylinders

Check HTEV is calibrated and working properly.
 

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I would just replace all the vacuum lines. It’s really easy it took me about an hour to do. I’m wrapping up my rebuild right now and that was the easiest part of the entire process
 

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Discussion Starter #8
Re: CBR 929 Stumbling in Mid Range, Runs Good on Top, seems to be dropping cylinders

I would just replace all the vacuum lines. It’s really easy it took me about an hour to do. I’m wrapping up my rebuild right now and that was the easiest part of the entire process
May give that a try just in case, thanks
 

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Re: CBR 929 Stumbling in Mid Range, Runs Good on Top, seems to be dropping cylinders

My 954 was running really rough at mid-RPM a few weeks ago. I noticed that the blinker rate was also very erratic when it was running rough. I suspected that the regulator was putting out an unstable voltage, messing with the injectors etc.

I changed the regulator and the bike has been running beautifully since. Maybe it's worth some effort for you to check whether the regulator output is stable?
 

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Discussion Starter #10
Re: CBR 929 Stumbling in Mid Range, Runs Good on Top, seems to be dropping cylinders

My 954 was running really rough at mid-RPM a few weeks ago. I noticed that the blinker rate was also very erratic when it was running rough. I suspected that the regulator was putting out an unstable voltage, messing with the injectors etc.

I changed the regulator and the bike has been running beautifully since. Maybe it's worth some effort for you to check whether the regulator output is stable?
Will give it a shot, I think I have swapped the regulator from my parts bike but have not actually verified the output is stable. Thanks
 

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Discussion Starter #11
Replaced vacuum lines and no difference. When going from idle to WOT on the stand it falls flat and then wakes back up, almost like 2-3 cylinders are shutting off and then coming back on. Would throttle bodies not being synced cause this or would that only affect the idle?
 
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