Choppy at 4000 rpms??

[VeryMetal]

I'm experiencing what I can only describe as a choppy feeling at 4000 rpms and just under in 3rd while cruising around. Almost like the bike is choking. Doesn't seem to happen while accelerating quickly through that rev range. What is this caused by?? Has anyone experienced this?

The bike is coming up for it's 12k mile service, somebody mentioned to me that I'd have to check the TPS (which I have determined to be the ECU? Am I right?). I have a chopped air box and after market pipes. To my knowledge it hasn't been dyno'd. Something I'd like to get done soon(ish). On a separate note, anyone know how much it costs to dyno a bike (roughly).

[Speeddog]

TPS is the Throttle Position Sensor, which the ECU looks at to decide fuel mixture and ignition timing.

To really benefit from the dyno, you would need to install a PCIII or similar device so that the mixture can be adjusted.
PCIII's are about $300 last I checked, and likely about the same $ to get a dyno-tune done.

Get your 12k service done first, see if that improves the situation.
And it's best to get the service prior to a PCIII/dyno tune anyway.

[Slide Panda]

I do have a Power Commander and recently was playing with the fuel tables.  One table I tried was lean in a specific range and lead to the bike felling choppy/herky jerking at constant throttle.  But it was smooth as I rolled through that point in the RPM range - so things sound similar.

Just for reference - it helps to know which monster we're talking about.  I could see a 620 lugging a big at lower RPMs where a 1000 or water cooled plant should be just fine

[Zipper]

MY PC III map was $250 about 3 weeks ago at Fast by Ferracci.  Good luck.