[NH Oldguy]

My 2009 G5 is prone to stumble coming off idle, or when rolling back on to the throttle after overrunning.  I have confirmed the EFI Throttle Position Indicator supply and output voltages are dead on spec at idle and WOT (thanks to singh5g for his excellent YouTube videos), and idle speed is OK.  The bike has behaved this way since I got it last year with about 2,000 miles on the clock.  It makes it difficult to ride smoothly rolling on and off when cornering, etc.

I have no experience with EFI, but it feels like a carbureted engine does if leaning out briefly just off idle.  Any suggestions for what I might do to improve this situation?  Thanks for any help you can provide.

[Arizoni]

About the only thing I can think of is that adding some Chevron Techron to a full tank of fuel might clean out anything that is plugging the fuel injector.

The bottle is made for a 12-15 gallon fuel tank so it doesn't take much in our little tanks to do the job.

[NH Oldguy]

Thanks for the Techron tip, Arizoni.  I'll give that a try.

I'm also wondering if adjusting the TPI to increase its output voltage a bit at idle would cause the ECU to fatten the idle mixture somewhat.  Does anyone have experience with tricks to tweak the ECU map, w/o going the Power Commander route?

[barenekd]

there is a big brass screw partly hidden by the tank that can be adjusted that can possibly take care of the problem, I had to move mine about a screw slot width clockwise to get the best setting, but I went almost a quarter turn fiddling with it. Be sure to mark its original position. I got it to the point that I only had a rare burp out of it. It was tolerable at that point. You can get a long slim screwdriver down into it with the tank still on it.
Bare

[NH Oldguy]

OK, bare, the "idle air bypass screw," as listed in the manual?  I will try tweaking that and the idle stop screw together to see what can be done.  And thanks for the reminder to mark the initial position......

[gashousegorilla]

Thanks for the Techron tip, Arizoni.  I'll give that a try.

I'm also wondering if adjusting the TPI to increase its output voltage a bit at idle would cause the ECU to fatten the idle mixture somewhat.  Does anyone have experience with tricks to tweak the ECU map, w/o going the Power Commander route?

   Adjusting the TPS voltage will lean or richen ACROSS the range.  Higher voltage richer.... lower voltage leaner. ...... You may or may not want it richer or leaner across the range.  You may want it at specific throttle positions and RPM ranges..........

   The air bye-pass screw will adjust idle.....  As Bare said, with very SMALL adjustments. And I wouldn't touch the throttle stop screw.

 Is your bike stock ?   Intake or Exhaust Mods ?  Just curious......

[NH Oldguy]

   Adjusting the TPS voltage will lean or richen ACROSS the range.  Higher voltage richer.... lower voltage leaner. ...... You may or may not want it richer or leaner across the range.  You may want it at specific throttle positions and RPM ranges..........

   The air bye-pass screw will adjust idle.....  As Bare said, with very SMALL adjustments. And I wouldn't touch the throttle stop screw.

 Is your bike stock ?   Intake or Exhaust Mods ?  Just curious......

Thanks.  That's what I had thought re TPS mixture impact across the range.  My engine is stock, except for the larger ID "English" head pipe from Hitchcock.