[spuggy]

I like the 2V air-cooled Monsters; simple, classic, well-proven design, easy to work on. Wants frequent (15K/3 year) belt changes, but they're cheap/easy to do.

Dirt cheap used. I bought an immaculate unmolested 900 with 8K-odd miles for 3K. I rate the EFI ones - but before they started using an electronic keys with the immobilizer tied to the ECU and the LCD clocks.

Which limits you to 2000-2002 MY; zero nanny aids, but does give you a good stiff frame (the later ones are stiffer still, no idea why you'd need that unless your last name was Rossi or Fogarty or something), good suspension (great suspension if you spring for the S with adjustable forks and a better rear shock) and brakes so good you'll have to train yourself to only use 2 fingers.

The 900 gives 80 HP (+10% more torque/HP everywhere with a DP ECU/flash, open airbox and DP mufflers - this also restores all the sub-3000 grunt that emissions control robbed you of, makes all thoughts of lowering 1st gear unnecessary and makes riding in town much more fun). You can lift the front wheel on throttle at the top of 2nd just by carelessly rolling it on too fast. Drop the front in the clamps and jack the rear suspension hoop by 1" if you want quicker steering still - stock is not exactly slow...

Riding position is basically "superbike bars with rearsets"; pretty comfortable with any wind to lean on at all.

If you want 120+ HP and nanny aids, disregard everything I said. Any faster than this is outside the "fun" envelope for me. A buddy had a monster S4 and ended up riding his 750SS all the time instead because it was much more fun than trying to keep the front wheel on the ground.

My car has better power-to-weight than the M900, but it's much harder to approach the limits on the Duke, because you'll just be on one wheel or the other.