where do i start? messy idle/accel on 1yr old bike

 Hi gents,

This just happened.  Beautiful 2010 harley FL has developed running
trouble while on loan to some jagoff that says it "just happened."

Idle swings between 850rpm and 2k, nearly stalling on the low side.
Backfires now and then when throttle is actually applied.  Throttle by
wire system.

One cylinder was not firing (rear) except during magic rpm intervals
on the highway when it would buck to life and the extra power would
pop in out of nowhere, only to cut out on decel.

Spark plugs were black - I swapped for new plugs and changed the map
on the powercommander v to be more lean.  Now the bike is louder and
stronger, but the idle issue above is still there.

Removed the PCV and reattached the o2 sensors.  No difference at idle
or at speed.

When she warms up, idle is very prone to stall - have to flick the
throttle constantly at a light.

103" stage II, v&h true duals + rinehart free flow slip ons.  Bike is
still under warranty but rather than bring it in I want to know what's
wrong and how to fix it.

Service manual suggests checking plugs, which is now moot since fresh
plugs are in (right?).   Googling around suggests checking fuel/air
lines.  I'm not really sure what to try since the bike is so new (only
6k miles).

Thank you for any and all help.

 

Hopefully, you won't do that again.

 WaIIy wrote:

snipped the symptoms

  Your first fuckup was letting someone borrow your bike . Your second was
trying to fix it yourself ,since you're obviously not competent to diagnose
and repair it.
  Take it to a dealer before you fuck it up to the point that even they
can't fix it .
--
Snag
Learning keeps
you young !

 On 5/9/2011 8:15 PM, Snag wrote:

Not to pile on, but this is my take on it too.

It may be something simple and easy to fix, in which case it's not too
big of a deal.  On the other hand it may be something major that the
guy screwed up, and having the dealer diagnose it will be the quickest
and surest way to figure out what happened, and whether your 'friend'
had anything to do with it.

Why do people lend their bikes to someone who doesn't have a clue about
bikes?  Must be a newbie thing.

My oldest brother let our middle brother ride his brand new 1975 (?)
Norton Commando 850 immediately after getting home from the dealership.
Of course the eager borrower didn't know anything about riding a bike
and immediately dumped it while riding around the yard.  Live and
learn, I guess.

 On 09/05/2011 8:18 PM, Mark Olson wrote:

My sense is many people, ok some people, consider bikes to be little
more than toys and are not concerned about passing them around to
friends or acquaintances.

I learned my lesson decades ago when a friend, and I use the term
loosely, borrowed my 150 Dream and returned it to me with a broken rod.
  When he gave me the keys he casually told me there was a funny noise
in the engine and I ought to have it looked at.

--
Disclaimer
Do not believe a thing I have said, unless you already know it to be
true, or can independently verify it from another source.

Reeky Ride To The Rockies
http://actualriders.ca/reekyrockies.htm