First of all, this is my first post here and I'm sorry it is going to be a long one.

I bought my bike last week and it was running perfectly and now not so much.

The bike- 2008 Nightster, 1900 miles, rush slip ons, big sucker, power commander 5 from Fuel Moto. Bike is clean as a whistle.

I had been taking some very short trips from home to work, so it is hard for me to remember exactly what preceded the loss of power. It happend shortly after my first fill up. I did use 91 octane. Also, right after the fillup i got denched by rain. Some day after that the bike started popping bad on deceleration and power was down. It would shutter a bit a low rpms.

I thought it could be plugs so i changed them (but didnt gap them). No change. I thought it could be gas cap venting because i screwed the gas cap down way too tight since it was sitting up high. Rode with it loose and no change.

So I drained the tank, put in seafoam, put in 93 octane gas and it seemed to have eliminated the backfiring but power seemed even worse- horrible in fact. I probably rode it 8 miles because i was pushed for time so that may not have been long enough.

So my plan for tonight is to gap the plug or even swap back the old ones- they looked fine. Any other ideas to try?

 

Sounds like maybe you got some bad gas. Also take your air filter off and make sure its not wet from the rain you got caught in.

 

You say you got wet,Some of the connections on the Nightster are not sealed as well as they should be ...so go through them spraying with some moisture repellent spray,also check for water behind the fuse box.
I hope you ar up and running soon,H.

 

The plug gaps could be pretty far off now(not that solves your original problem, but worth checking). Did the intake suck in a lot of water?

 

I changed the plugs back to the old ones because they are fine. I rode it 20 miles and no real change. Next step is to check for water in the intake and fuse panel. I will also try to pull the fault codes. If these don't work i am going to remove the power commander and use the oem settings- just to see if it makes a difference.

It drives like it is partially starved for fuel, air or spark (duh), just don't know which one.

 

Sounds like a tuning issue to me.

 

Hmmmm...good idea, the power commander could have failed. That's the reason my dealer is urging me to use the HD race tuner. There's nothing left on the bike that could be damaged by water.

 

Honestly, all the symptoms fit. Backfiring, crappy performance, sputtering. Sounds like fuel management issues here. The timing is probably off. I would reset the PCV and probably install the maps again. Personally, I think all of those cookie cutter tuners are garbage.

 

I vote for water in the gas.

 

I completely removed the Power Commander- no change. I checked the air cleaner and the fuses- no moisture that I could see. I pulled the fault codes for the ignition- there were none. I am at a loss. I suspect the injectors but I may just take the bike to a mechanic. Very frustrating.