I had a low rythmthic vibration on my 2012 speedmaster after removing the emissions and adding scepter exhaust.
i never changed the tires on that bike while I had it.
after lots of fooling with the chain. and being quite annoyed. it ended up being a tune issue. specifically an FL map switching issue. sort of the ECU looking at the wrong fuel map at the wrong throttle opening. So it made it hunt and surge slightly. giving the feel of a harmonic.
the dealer had originally thought a MAP hose issue, but that did not fix it. although you might check your MAP lines as they are easy to do. If leaking it would run for crap most of the time.
when you say you added a circuit to not get a engine code light, was that a plug into where the air pump went?
are the O2 sensors still attached to the wire harness?
or did you plug optimizers into the sensor plugs?
have you or the deal plugged into the ECU to see if there are any error codes? THe MAP condition would show then as well.
You could have masked a engine light with that add on bit.
05 speedmaster - 1100cc, 11:1 racing pistons, Carillo rods, thunderbike cams, ported and polished head, 2mm over intake and exhaust valves, Barnett kevlar clutch, scepter pipes, oversize manifolds, 45mm HSR's, TTP stage 4 firestarter
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