If you're into mods in significant $$ to raise the MPG:
1. Get an old cam that's lost some of its lift. More than 75000 miles ought to do it.
2. Use the HM341 pipes, or at least add some back pressure if you have aftermarket pipes. This will cut hi-end HP, but it will boost midrange torque, which is where most of us ride, anyway. Then, you can lean down the mainjets a step or two, which will also improve the MPG.
3. Get Dyna hi-output coils, like their 3-ohm units. Be sure to add resistors to them if you do, or the added electrical load will lose the MPG benefit in other ways, and cause electrical headaches you may not want.
4. Run a standard headlight (not halogen) and 1034 taillight bulb to reduce electrical loads. These use HP, too.
5. Make sure your chain is REAL smooth, and the sprockets, too. Keep them lubed.
6. Add PSI to your tires, but not too much (or you will reduce tire patch size). The best rule: start with the PSI on the bike's label, then ride it about 10 miles until the tires feel warm. Read the PSI then. If it rises more than 2 PSI cold-to-warm, then add 2 PSI and try again, next day. When you reach the "magic" 2 PSI rise, you've found the perfect pressure for your ride, weight, and tire contact patch size. This varies with every tire, rider and bike, so only you can make this test work. While you're at it: look closely at your tires. Too large a tire size will drop MPG like trying to hold warm Jello in your hand. Stick close to the recommended sizes for best results.
7. Someone else said I should add this, so I'm trying to NOT make this an "ad": use the Transistorized Ignition. It does improve MPG a bit, but on my bike it's only about 1-3 MPG, depending on the traffic (but, I always keep mine in pristine tune, too). Generally, the Dyna "S" will not improve MPG over a well-tuned bike, but the Dyna III can (and possibly some of the newer digital ones).
