Step 2: Picking the motor
For the electrically challenged note that it's a motor, not an engine. Engines have 200+ moving parts, and need to be serviced and fed explosive fuel, motors have 1 moving part, don't need servicing and can run on sunlight if you really wanted them to.
So there are a lot of motors around in the ebike world. The one I used on my bike was a Crystalyte 5305. It weighs 12kg and has bucket loads of tordue. Motors have advanced since then, and Crystalyte don't make that motor anymore. In it's place there are a number of other motors. Of course you could also shop at other manufacturers, but if you want good value for money I'd stick to Crystalyte. Whatever you do though, don't buy a cheap geared hub motor from ebay, all that will happen is that you'll get a motor that strips it's gears the first time you actually apply any throttle. Direct drive hubs are far more reliable, and far quieter.
To get to 65km/h, which is of course plenty fast on a regular bicycle, I'm going to recommend the Crystalyte H4065. That 65 at the end there means this motor does 65km/h with a 72v battery in a 26 inch wheel. They also make a H4080, which does 80km/h, but you get more speed for less torque, and trust me, you don't need any more speed. I'd much rather have a lower top end and accelerate so hard my balls ache! The motors with more torque are also far kinder on the controller, so you're less likely to blow up controllers (we'll choose those later) in the long run. Incidently the 5305 I chose was also the motor with the most torque, and I am yet to blow anything up. At least nothing bicycle related!
So how does this motor perform. Well I haven't ridden one, but many people I know have. Here's a couple of videos for you.
Acceleration:
As you can see things get pretty good once you up the voltage. The bike I'm recommending here runs 76.8v nominal, but will spend most of it's time in the 79v range. For those who haven't tried electric power, I can only describe the feeling as being shot out of a giant kettie. It's one long wave of power, and it's always there. Instantly. No gears to change or clutches to release. Sadly this also means that I don't let too many people ride my bike. It's got a 2 from 4 record, half the people to have tried it have been thrown off at some stage. Now I have a power limiting switch...
If you're in the mood for some hill climbing, here's a quick test on a very steep slope:
I use my bike on most of the mountain bike trails, delta park, emmerentia etc, and I've never come across a hill that steep. It's nice to know that if you did there'd be power to do it. It would likely even be easier as I'd approach with speed. All in all I think it's a pretty impressive motor, and you save about 3kg in weight over the bike I've got.
