The difference from shit to Holy shit! just the sound is different from Mikunis 41's seem to be over kill unless you have a "worked" motor. I love my 39's.I have a 1117 motor worked on by Schnitz Racing or so I was told all that stuffed into a 600 frame makes things very interesting. Downsides, ther'e gas hogs and you'll have to run a Pingel Petcock, and there's no choke so you'll have to come up with a method starting her up on cold mornings.
Bobbychet
Bobbychet