this is a newbie question, is it possible to reduce the engine size of a H D bike?

i mean like buying a fatboy with 500cc engine?

 

No, just buy a Harley Street 500...

 

Well you could take one of the spark plug leads off ! lol...b.

 

No! Why do you ask? Tell us more.

 

technically yes you can. but it will be $$$$$
back in the last half century, there were one lung sportsters and BT's. there were sportsters with one 1200 jug also.
afraid of too much power??? install a throttle stop of reprogram the rev limiter to a lower value. truth be told, go buy a honda of your required size, they mastered this world before hd cut their teeth.