J&P Community

 My girls '06 1200 custom started recently misfiring badly after the bike gets good and hot- to the point that it wont stay running at idle, but runs great at speed. Its a sudden problem; no mods recently (like 2 yrs). It only does it when it gets HOT- like after 10-15 miles on hot day or a good 30 minutes idling only ( or when oil temp gets to about  150). Doesnt seem like idle circuit or other fuel related issue - plus - its more of a complete misfire with backfire up through carb- almost like ignition gets stuck in advance at some point when bike gets hot. But runs great at 1500 rpm and above. I wouldnt imagine if it were an intake leak or clogged slow speed jet or something, that it would take so long for it to start acting up. I was going to start with ignition system to find problem but im not familiar with troubleshooting on these bikes. Any help with diagnosing ignition culprit (like map sensor, crank pos. sensor, coil, icm) would be great so i dont waste money replacing something thats fine. Thanks!!! 

PS: only mods are Sampson exhaust and hypercharger air cleaner.

Mk,

 In the first place, Idling for 30 minutes is a no no. I don't think the '06  XL's have map sensor, crank pos. sensor, icm. Sounds like the ignition module is breaking down when it gets hot.........A dealer may be able to check it out. The coil wouldn't react that way, when they go, it's usually high RPM that's effected.

 fx: 

i know, i know... but was trying to replicate conditions to get it to act up while looking for intake leaks and such... traffic around here is bad so when it starts acting up it gets tough to keep going.  Anyway - yes, they do have all those wonderfull sensors according to the HD shop manual for '06s, including bank angle sensor which will cut of ignition if leaned over past 45 deg. for certain period. I  can see the map sensor right on top of the intake manifold.  Manual references another manual for troubleshooting those components. I figured someone may know how to do that.  Dealer is last resort. Thanks

MK,

  And another one bites the dust. They actually did that new fangled electronic marvel of modern technology to the Sportsters? Heard they did, but didn't think it was that early.................Those systems on the big twins have their own diagnostic capabilities. Check the manual if there's a way to read trouble codes.

 i don't know the 06 well but my 92 had the same simptoms a few times. i found that a battery post was shorting once. And it had vibrated just lose enough the second time. hope it's that simple...