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stumbles and hesitates at around 4k rpm

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1.9K views 5 replies 1 participant last post by  duc44  
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#1 ·
I changed the plugs and tested my bike because I was having a problem with the way it runs. I noticed that it stumbles at around 4000-5000 rpm. When I looked at my plugs it looks like the vertical cylinder is running fine the color of the tips of the plug is milky brown. The horizontal(front) cylinder is running a bit lean. Can I adjust the air screw to compensate for this? Anyway I'm going to bring my bike back to the dealer to sort things out this week.
 
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#3 ·
Sorry I forgot to indicate that my bike is a 750ss ie with only 3k mileage. But I think the motor is the same as the m750 ie. This site has so many active members that's why I decided to post my problems here. Well anyway, my bike hesitates and has pop like sound coming from the tank or underneath it, it sounds like a hiccup.
 
#4 ·
from your description it sounds like your bike is backfiring through the intake most likely from running lean. don't touch the air screw. it will make no difference at that speed and you will through the bike out of sink. 3K miles? take it back to the dealer. most likely, either the bike needs a tweak with the Mathesis or a sensor is out of wack. new plugs wouldn't hurt either. if you are running premium fuel, try el cheapo 87.
 
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#5 ·
Had the same problem on my 900SSie. A throttle-body sync, and a cam-degree cleared it right up. Mine was stumbling and popping around 2-3K, and mainly at minimal throttle input. If your WOT, and it starts stumbling in that range, its probrobly something else.
 
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#6 ·
Thanks guys, will bring it back to the dealer this week. One more thing, I noticed that my the color of the sparkplugs are not the same . Looks like the one at the rear cylinder (vert) is richer than the front( horizontal). Is this a sign of my throttle body not in sync?