coming home from a ride, bike lost some power, still running fine, idles fine, starts fine, plugs look good. Did a compression check, the rear cylinder is down a few psi, but do not think thats the problem. the fact that the power loss was sudden, leads me to believe something mechanical, maybe fuel pump, compression relief?, anyone have any guessses on what I should check, its is a 03 anniversary, thanks in advance.

 

Are you running a peripheral tuner or is it the factory computer?

 

It is the old screaming eagle brown box tuner, plugs read good, not wet, both are consistent burn. Runs great till you really roll into the power, doesnt stumble or sputter, just down a sizable amount of power

 

Might be that tuner.

 

Is there any way to test or run a diagnostic on these?

 

Probably, but I do not know for sure. Remove it and do a short test run.