In 3500 miles of riding my motorized bike, I have yet to encounter a single pedal cyclist who can even come close to keeping up with me.
Sometimes if I come upon a really good rider, I fool with them a little. I slow down to their speed (which feels painfully slow) to see if they will race me. If so, I stay with them for a while until we get to a good size hill and then I go full throttle and blow them away. When I get to the top, I am continually amazed at how far back even the strongest cyclists are.
ill say i have been passed two times by road bikes once on a straight away i passed up to spandexers and they took it personaly and passed me up but they couldnt keep up for long and turned left on the first street they could find i followed to see how long they could keep up the speed they actually kept ahead of me for a couple blocks and when we came to a red light they were so exausted looking breathing heavily and dripping sweat i couldnt control my laughter these guys trying to prove some sort of point that they can go faster than a motorbike but they cant outlast a motor bike
the second i passed up a road bike and he slowly fell back farther and farther till we hit a nice down hill he took the lead my motor was reved out and like the spandwexers he turned left on the first street he could find
but then again i weigh about 250 and my bike weighs at least 60 or 70 loaded down with supplies and a stock motor with 44tooth sprocket i feel 25 mph is pretty good cruising speed