I've had this Puch Moped for nearly a decade. It's followed me to multiple houses, and in all that time I've never managed to get it running. At this point I've rebuild or replaced everything related to the drivetrain, fuel delivery, ignition... it just doesn't want to cooperate.
And even if I could get the thing running, it makes a peak of 2HP. At 8500' above sea level that's effectively about 1.6HP (as a general rule of thumb, a naturally aspirated engine will make about 20% less power at this elevation due to reduced air density). 1.6HP isn't quite enough to carry ~80lbs of moped and ~220lbs of rider and gear up the 8-10% inclines we have in the area.
Even if I could get the gasoline engine running, I'm limited in how much performance I can eke out of 49cc's of displacement. But there's another way! With the widespread availability of electric swap kits for standard bicycles, I have a plethora of options for improving the performance of this moped, while also shedding weight. Plus, these kits allow for a ton of flexibility. I have the option to retain pedals, I can go FWD/RWD or even AWD, I can add more robust electrical components (better headlight, brake lights, turn signals, even a horn).
I've been researching various options for years, and finaly settled on a swap kit. The BAFANG BBS02B is a 750W mid-mount motor designed to drive the rear wheel of a road or mountain bike. The kit comes with a handlebar-mounted display, integrated brake circuit, and a 20Ah battery @ 52V. It can also power secondary devices easily, via a 5V 500mA USB port. Plus, the whole kit weighs about 15lbs - much lighter than the ~40lbs of engine, transmission, exhaust, carburator, and filter box.
There are a few key features of this kit that really drew me in:
At this point, I'm still in the disassembly stage. Once the moped has been fully disassembled, I'll strip the old paint and use my HVLP gun to lay down fresh paint. I'm hoping to replicate the original Puch burgundy for the body, and maybe leave the front fork and rear suspension a different color. I'll also take some measurements from the original motor mounting area so I can work on developing brackets to mount the BAFANG motor. I do have another Puch moped with some usable parts, so I'll start stripping that one down as well. The final product will be a combination of parts from both mopeds.
Additional items include:
Construction is complete, and the moped runs!
My original thought was to strip all of the paint, sandblast the frame and major components, and then apply a fresh coat of paint. However, the patina of the moped really started to grow on me. There's something cool about the old burgundy paint and its collection of scuffs, scratches, and other minor damage. Plus, I may need to make other modifications (damaging fresh paint in the process).
With the new goal in mind, I started construction of a bracket to mount the BAFANG motor. The Puch engine and transmission mount to the base of the frame with three long bolts which pass through both sides of the frame and the engine/transmission case. The BAFANG motor attaches to a tubular bottom mount (pretty much universal on pedal bikes). So, my custom bracket needed three holes to mount to the frame, plus a tubular bottom mount for the new motor. I did most of my prototyping with cardboard here (ask your local gas station for some empty cigarette cartons, the carboard is sturdy and easy to cut).
After a few iterations, I settled on a shape that would fit nicely, complement the style of the bike, and be relatively easy to cut with just an angle grinder. The bracket got a few coats of flat black Rustoleum paint to prevent rust and hide the bare metal. In the interest of simplicity, I used six bolts to "clamp" the bracket to the sides of the frame. This results in an extremely sturdy bracket which can support the entire weight of the moped. Although the material is thin, most stresses are distributed along the plane of the bracket. Although it's not visible in the photos, I also added a small bumper to the front of the bracket to keep the motor precisely positioned. This ensures the motor won't rotate and change the chain length, which could cause problems.
I also needed to create a new chain for this application. While a standard bike chain would have worked, I was a bit concerned about longevity with the total weight of the bike and rider. The Puch's engine drive train is much stouter and was still in good shape. It was also a bit too short to fit with the huge front sprocket, so I grabbed a few links from a second chain and lengthened the original one until I had something that would work. Fortunately, both the rear wheel and the motor can be adjusted slightly to take in slack, so I was able to get a good fit with barely any deflection. I was a bit worried about this part, but the sprocket on the original moped wheel and the sprocket on the BAFANG motor were compatible!
With the motor mounted, I ran a few tests. My sprockets lined up perfectly, so no need for additional shims or spacing. I made sure that everything rotated freely, and lubricated the rear wheels I tested all the wiring and controls to make sure the display and throttle worked and reflected correct values. While doing this, I also adjusted the wheel size in the BAFANG configuration. The controller uses a simple hall effect sensor to detect wheel rotations, but it was preconfigured for a 26" wheel. These wheels are 22", which would limit my top speed to about 21.2mph. At some point I will make some additional configuration changes to the motor, but for now my goal is to get the bike running.
In addition to the motor and battery kit, I needed a few extra parts:
Most of these were simple bolt-on pieces, but the seat deserves a special mention. I like the cafe racer style, so I went with a long saddle instead of a standard bike seat. However, most of these are designed for use on motorcycles, not bikes/mopeds. As such, I decided to modify the original seat base so I could mount the new saddle directly to that. This required a few cuts with the angle grinder, and some extra metal to support the seat. The modified seat isn't terribly pretty (I mis-measured a few times) but it's very sturdy and easily holds my weight. There's an extra pin which prevents side to side movement (or more accurately, rotation around the mounting post) which was a concern of mine due to the longer seat and additional leverage. I also mounted the battery right in front of the seat, which helps keep it from moving as well.
The finished product (well, without the headlight)! Did it meet my expectations?
I still have some loose ends to tie up here, mostly related to cable management. I'm also going to add a brake/running light on the rear. The shocks definitely need attention, as they're way stiffer than they should be (probably rusted). For now, the project is mothballed until the snow melts a bit and I can really test it! I'm also considering building one of these for my partner, but giving her the 750W motor I used and purchasing a 1000W motor for myself (she weighs about 70lbs less than I do, so she'll still have a great power to weight ratio).
Website coded by Delta Sierra, all content copyright Delta Sierra (unless otherwise noted). Hosting provided by Neocities.