Hello! First of all i would like to say hello to everybody. I'm Alberto, i'm 44 and i live in Roma, Italy.
I own a Dyna Street Bob 2006. I'm not english language native, so i'll try to do my best.
My bike got an issue i really can't understand.
Bike starts ok, then i go around a bit.
After a while, when i am still i.e. at a stoplight the RPMs go a little bit high all themselves, when i try to half or full throttle, the engine cuts off almost switching off, so i have to be careful to move again, like releasing the clutch and giving 0.1% throttle. Eventually if i give too much throttle the engine definetely switch off.
Then to restart it i have to run a lot the starter and i have to give full throttle. The engine got difficulty to restart, i have to full throttle while running the starter. It stutters, looks like it is starting, then nothing, 3 or 4 times and then finally it ignintes again. I can smell a strong fuel scent, and mufflers spit a black smoke for a while.
Usually when i feel the RMPs going high, if i stay stop and wait, the RPMs will go down again and everything is ok.
After this happens, also after restarting the bike, the engine stutters a bit, then when i go like 50mph everything seems fine.

What i have done so far: 2 full tank cycles with octane powered fuel.
Replaced sparks.
Replaced fuel pump and the small filter.
Replaced IAC.
Replaced TPS.
Cleaned air filter.
Replaced Speed Sensor.

But you know, problem still might be about these components.
No error codes in DIAG.
Just some days ago i got a P1356 (Rear Cylinder No Combustion) error, but i don't think it is related, looks like more it is a consequence.

Bike got open SE mufflers, open filter, and hand tuned original ECU. After these mods bike was perfect. Problem i described is happening after 2 years, out of nowhere.
Bike got big 95.000 km, but i maintain it like it is an oracle, oil change every 6000km, always indoor garage, ecc... ecc... you know, we are HD bikers.

I am really going crazy with this and i don't know what to do.
I thanks anyone who could have some clue. Really appreciated.
Bye!

 

Have you tried checking for intake leaks?
These bikes can do some odd things if the battery connections are not tight and clean. Especially the ground cable connection. I would also load test the battery. I know these are basic simple things but they are often overlooked.

 

Thank Nevil for the suggestions!
Intake is clean and functional, filter clean and replaced new IAC. By "leaks" i don't really understand the meaning, like the air can't get inside well? Or there is dispersion and scatter after entering the filter? (sorry i don't speak english natively)
Battery changed some weeks ago, bike starts like clockwork, should be ok. Only thing is an USB connection attached, but there is a switch on off, anyways i will try to cut it off from the circuit.
Thanks again.

 

Intakes can leak where the manifold flange meets the head. To check, first warm up the motor. You can use a propane torch (unlit) or something like throttle body cleaner. With the motor idling, being careful not to spray into the air filter area, move the gas or spray around the flanges. If there is a change in the idle you have a leak. You can probably find some videos on line which might help visualize this process.