Mid Sized Cruiser with good fuel economy that can drive a side car?

Hello out there.  This is my first post!  I am interested in purchasing a used bike that is reasonably fuel efficient, has a nice smooth engine (have prostate trouble and must have smooth), and can pull a Velorex side car.  My wife and I plan to take day and perhaps weekend trips and will travel on local and secondary highways for the most part.  I would also like to have shaft drive and a reasonable sized gas tank with a fuel gauge.  Any help would be greatly appreciated.  Cheers,  Dub  

Most cruisers use V-twin engines, which are not smooth. A smooth running V-twin still shudders, shakes and pounds when compared to just about anything other than a single cylinder engine. The V-4 engines can be smooth, but they don't come in the midsized bikes.

Fuel efficiency is usually better in carburated bikes, at least it was before they started using air injection to burn off excess fuel in the exhaust pipes. A carburated two cylinder bike can easily be tuned to get more than 50 mpg even at 70 mph. Fuel injection requires remapping of the FI computer to stop it from wasting gas.

Your requirements seem to be contradictory. Fuel efficiency requires as few cylinders as possible, while smooth requires more cylinders. The smoothest two cylinder engines are the opposed twins, but the BMW R-Series are standard bikes, rather than cruisers.

regards,
Joe  

Not entirely in agreement with you(no surprise there). You are right about the v-twin, lub-dub-pause to slow down, lub-dub... That 1st cyl is always trying to speed it up. Wife had a thumper that got about 65mpg. There was no variance in load between cylinders.
4 cyl bikes like the Magna used to be common, but in the cruiser market, they have been cast aside.
Parallel twin (or the BMW boxer) should be the most efficient since they fire exactly out of phase.
But, back to the sidecar issue, I've seen a Boulevard 800 triked out. It has shaft drive, it should get mid 40s for mpg. I think that's going to be the best you can get, just because of the additional weight, and increased rolling resistance.  

I have heard that the Triumph Thunderbird and American/Speedmaster are very smooth bikes and get reasonable gas mileage.  Perhaps other members have experience with these bikes?  

If you're serious about a sidecar see www.ural.com for info about the only rig available that is designed specifically for sidecar use. Due to the cost of mods required to add a sidecar to a regular motorcycle, perhaps putting up with the cost and operational quirks of a Ural is not such bad idea.