I did both, in stages. Couple months ago, I put a 33 tooth pulley on Belle. The performance is as you read, the MPG was roughly the same. Then a couple weeks ago, I installed the euro gears. Again, performance you have read about. MPG? Unknown yet. The tank came off, so I lost the trip numbers, and then the Rostra went on, again losing the trip numbers. I think it may be *slightly* better, but that is mathematically induced. Before the changes, I would ride 100 miles, the odo would read 110, so MPG would be high. Now 100=100, so it would fall off some. This is balanced by the engine working less, and being more efficient.
Agree on Excedra's. I have about 1k miles on mine and already see the wear on the rear. Darkside is next.
The rostra is on and working. Not smooth at all, surges real bad at low speed, with magnets. It may need a longer actuator arm, I am not sure. Posted for "wiring help", but it apparently isn't common enough for much to be out there.
Rubber side down.
1976 KZ900A4 (restoration project)