Hi Kyle,
I tried to copy/ paste some info from someone "in the know", a seasoned bicycle pro (mechanic/retail)? (pics did not go through)
"C" - Thank you again for sharing your knowledge.
Sos not to upset anyone, pm me and ill get you the link.
I say do it right the first time, I wish I did in hindsight.
Good Luck and please post your build updates!
Heres the info (below): --->
"Good" would be something like a basic cruiser, new or used, from a bike shop-- Sun is a brand that most bike shops can get. I don't claim that it is better than other basic cruisers from bike shops, only that it is available just about everywhere, and it's a cut above things like the Huffy Cranbrook. Note that one of the main reasons a cheap bike like this would be qualitatively better than a department store bike is the fact that it has (probably) been prepped by a bike shop, which will support you with warranty service and often with a free tuneup at a later time. Here's the Sun Revolutions, which has a steel frame and aluminum rims and sells for about $200 full retail:
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For ease of mounting a motor, for maximum strength and stiffness-to-weight ratio, etc., a step up from that would be a straight-tube cruiser like the Sun Boardwalk Type R. It has an oversized aluminum frame, but its straight round tubing should make motor mounting more reliable and possibly less complicated than using a traditional curved tube frame. It's a heavy duty bike intended for rental fleets, and it comes with the 12ga spokes that seem to improve reliability with rag joint sprockets (although they do not improve upon 14ga spokes for pedal bike use).
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Either one of the above bikes would need a front brake added to be complete and safe at motorized speeds.
Worksman and Husky industrial (and the on again, off again Schwinn Heavy Duti) bikes are a mixed bag. Their frames are sturdy steel, their components are MB-ready, and as far as I know they are built up by people who care that they work properly. But the frames all feature double top tubes that crowd your engine and limit mounting options, and some of their tubes are curved. Their stock brakes are all inadequate. Of the three, I think the Schwinn combines a straight seat tube and down tube with a little more room for the engine, and thus would be the best choice. But it costs more than the other two.
All of the above-- all cruisers, basically-- come in only one size. That makes about as much sense as one size of pants for everybody. If you are very close to average size, it isn't much of a problem, but if you are short or tall or oddly proportioned, you're out of luck.
Bike shop quality mountain bikes and city bikes come in multiple sizes. There is a huge variety to choose from, so you can be picky about details. For motorized bike conversion, you want to bias towards a steel frame with plenty of room inside the front triangle, straight round tubes, and simple rugged construction. Fortunately, all these things put you in the lower price ranges.
A cheap suspension fork is a liability. Either get a good hydraulic model or stick with a rigid fork.
When you combine a steel frame with a rigid fork and simple, rugged construction, a lot of your remaining choices are single speed mountain bikes. These have all the virtues of cruisers but few of the drawbacks. They have two strong brakes. Many of them come with disc-ready wheels, so you can bolt a sprocket right onto the ISO rotor mount with no rag joint and no runout. Here is the Redline Monocog 26, a good and no-nonsense example of the breed:
It's easy and cheap to swap a cruiser style handlebar onto a mountain bike if that suits you better.
If you like having multiple gears, you can save money and get an even roomier home for your motor kit by buying a pre-1990 (pre-suspension) vintage steel MTB with a level top tube. These bikes are all very durable, and they offer the biggest interior space in the front triangle you can get for any given frame size. They have more laid-back and cruiser-like geometry than modern mountain bikes, and you can often find them for less than $200 in roadworthy condition. Here's a 1985 Mongoose ATB, which is typical in most regards:
"Best" in my opinion for a motorized bicycle conversion would be something like a modern steel single speed MTB or an '80s steel MTB, but equipped with a NuVinci, Shimano Alfine 8, or other disc compatible wide range internal gear hub. To this you could add a Sick Bike Parts shift kit for maximum performance, or a Manic Mechanic rotor mount sprocket for maximum tidiness and simplicity. You'd have a bike that was a pleasure to ride with the motor off-- but safe, robust and efficient under motor power. If cost were not a major factor, I'd have a bike shop build some seriously heavy-duty wheels with chunky double-walled aluminum rims and 13/14ga butted spokes, and I'd use a pair of top quality linear pull brakes with Kool Stop pads and brake booster arches.
