CBR 600F 1987 - 1990 CBR 600F Forum

cbr600f 90 backfires and not run well HELP

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Old Sep 10, 2015 | 03:30 PM
  #11  
dennisgb's Avatar
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After listening to your video I have a couple of questions.


The pipe you have on the bike sounds like an open design. This style of pipe may result in the sounds you are hearing.


Given that, did you rejet your carbs for this pipe? I would be concerned about fuel air mixture and you may want to stick a sniffer (O2 sensor) in the pipe to get a reading.


When you cleaned the carbs did you remove the jets and make sure they are open? Pilot jet usually requires a probe (wire) to clean it properly. What are the pilot screws set at? Did you remove the pilot screws and clean them and the orifices? Pilot circuit on these carbs must be absolutely clean and set properly or bike will not run right.


This sound your hearing does not seem to be related to any electrical problem...it sounds like a mixture issue to me. You may not be able to tune it out with that pipe.
 
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Old Sep 10, 2015 | 03:34 PM
  #12  
desiprika's Avatar
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Originally Posted by dennisgb
After listening to your video I have a couple of questions.


The pipe you have on the bike sounds like an open design. This style of pipe may result in the sounds you are hearing.


Given that, did you rejet your carbs for this pipe? I would be concerned about fuel air mixture and you may want to stick a sniffer (O2 sensor) in the pipe to get a reading.


When you cleaned the carbs did you remove the jets and make sure they are open? Pilot jet usually requires a probe (wire) to clean it properly. What are the pilot screws set at? Did you remove the pilot screws and clean them and the orifices? Pilot circuit on these carbs must be absolutely clean and set properly or bike will not run right.


This sound your hearing does not seem to be related to any electrical problem...it sounds like a mixture issue to me. You may not be able to tune it out with that pipe.

Thanks for info denis. I have 6sigma jet kit, pilot jets are 42 size. mixture screws are on 2/5 turns. You might be right maybe carbs are not clean well who knows.. i will try again since i got 1 pair of carbs extra so i will try with them also but how do you explain this stator issue about voltage..? Thanks bothers me, thats why i dont pay more attention on carbbs and other. Thanks
 
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Old Sep 10, 2015 | 05:06 PM
  #13  
Doc B.'s Avatar
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30VAC at the yellow wires sounds like your stator is good. Just to clarify, you need to switch the meter to DC volts and measure at the battery terminals (not the stator wires) to see if the r/r voltage is correct. You should see around 13.5-15VDC across the battery terminals with the motor running and around 12VDC with the motor off.

And to support Denny's comments, I had problems with the pilot circuit (and the choke enrichment circuit too) that required me to go in a couple of times and clean them out with spray carb cleaner and compressed air. I kept getting gunk in the tiniest passages from somewhere upstream and the motor would miss on one or sometimes two cylinders below about 5K. After a couple/three tries I got it all cleaned out and it runs consistently.
 
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