Puch eMaxi Build

[AGS]

Hi all, I have had some requests to post a build thread, so I would like to share my build with you. It is based on a 1984 Puch Maxi S that I bought from a motorcycle auction in boxes with a registration document so it will be road legal. These mopeds are becoming difficult to find now, especially one that is registered and I didn’t want to butcher a good example so this was ideal for my project.

I have used a QS205 hub motor mounted in a 19” wheel and a MQ CON Sabvoton 72100 controller. The frame needed a rear fender chop to accommodate the wheel.

Here is the freshly painted frame with the rear fender chopped ready for the build. It was pretty scabby and I’m pleased with the result considering it was a rattle can respray in my garage on a cold winter day, so not the ideal environment for spraying a frame. But I managed to get a bit of shine on it with no runs or orange peel using an industrial acrylic spray paint.



The first thing to do was to fit new headset bearing cups and pedal bushes. I’m replacing the pedal assembly with foot pegs.

I also fettled a 40mm plastic push fit waste socket to bung up the air filter hole and made a simple tool to press in the bearing cups instead of hammering them in.











The next job was to fit a new swing arm. Here is a MLM race swing arm compared to the original. The MLM arm has a 130mm dropout and it needs to be 150mm to 155mm to accommodate the hub motor, so I made a jig to cold set one side at a time and to pull the axle flats back to parallel after stretching.

 

[AGS]

Here is a new EBR 83cm front fork assembly compared to the original 53cm forks and a new pair of MKX 360mm shock absorbers compared to the 300mm originals.

The long forks mean a 10cm extended front brake cable is needed. I also have an additional stabiliser, because the mudguard stabiliser is not strong enough on its own for these extra long forks.

360mm on the rear is the biggest I can fit and the shocks will provide 50mm of spring compression before the rear wheel touches the fender. I also have a new chrome mudguard and flat handlebar.



I’m keeping the original front light and I needed to make a couple of shims for the front indicator brackets using 28mm end feed copper fittings with a slot cut in each one so they slide onto the fork leg. I bought 28mm brackets, but they needed a bit of help to clamp tight enough around the fork leg.

The bright orange horn operates at 72V and draws only 250mA, so it’s ideal for my build. I have “crudely” mounted a magnetic brake switch on the front brake lever, but it will work fine for the motor cut out and brake light.







I needed to find a new solution for the tail light after chopping the fender so I made some parts to mount the tail light, indicators and registration plate. The part on the right came with the tail light but I chopped and re bent it to suit my build. I made a cap for the tail light out of a couple of plumbing waste fittings using a small piece of 32mm pipe and a 40mm push fit end cap, cut and glued onto the pipe.

 

[AGS]

2.75” x 19” rear tyre is the biggest that I could get to fit on this frame and swing arm. I also bolted on a SRAM 203mm brake disk. The swing arm didn’t have a caliper mount so I needed to make one using 5mm steel plate. I also made some 1.2mm shims to take up the slack for the axle. The swing arm is built for a 12mm axle and the motor axle is 10mm across the flats, so the shims keep the axle nice and snug in the slot with no slop. I have used a Talaria hydraulic brake assembly because it has a sight glass for the brake fluid and a ball end lever. It conveniently comes with an integrated brake switch.

I also have a 25cm side stand which just about does the job, although there is quite a lean when on the side stand.







I built a controller box and I also bought an EBR frame brace. The frame brace needed a bit of fettling to fit because the holes were in the wrong place, but that was already explained by the supplier, so there was no surprise when I found it didn’t fit straight out of the box. I found a saddle that I liked on eBay, mainly because it was black and white to match the colour theme of the bike. The original seat base was rotten and needed the rear rack fitted to mount it properly and I wanted a less fussy rear end.

 

[AGS]

Here is the auxiliary control panel for head light, tail light, brake light and indicators. It’s just a simple 72V to 12V converter and a bunch of relays.



And this is the MQ CON 72100 Sabvoton controller with a 125A dc circuit breaker. It also has an alarm/immobiliser that works well. It doesn’t completely lock the motor, but it does make it cog and it’s difficult to push the moped when the motor is cogging.



The front indicators need to be a minimum of 240mm apart so a couple of extension brackets were needed. The minimum distance between the rear indicators needs to be 180mm.

 

[AGS]

I made a bottom mount and a battery box that will house a 72V, 150A, 50AH battery.



The birds nest wiring isn’t as scary as it looks and I labelled every cable to make it easy to connect up properly.





The cockpit is pretty full, left to right:

1. Talaria rear hydraulic brake assembly
2. Auxiliary switch for lights, horn and indicators
3. Display buttons
4. Display
5. 12V auxiliary switch
6. 72V ignition switch
7. Magura mechanical brake
8. Full twist throttle.

 

[AGS]

Here is the moped outside parked next to the Greaser and Lotus.




And here are a few photos of the moped parked by the river with the registration plate removed.

 

[guerney]

At last, your Maxi Puch thread! What's it like to ride?

 

[AGS]

Yeah, it rides very well. I’m pleased that the battery hasn’t ruined the CoG.

It’s a heavy bugger though. Now weighs 75Kg, which is about the same weight as a Honda SS50.

The turning circle is a bit of a joke, because I have fitted chopper forks but that doesn’t seem to affect the ride because I have compensated by fitting huge rear shocks.

The standard front brake is appalling. The rear brake is very good, it’s much more powerful than the front.

I have initially set the electronic brake current to 30 Amps, but I may increase it to 50 Amps.

I haven’t played with the controller settings much yet. Regenerative braking is still switched off and so is field weakening.

I have done around 10 miles on it so far and nothing has fallen off yet.

 

[AGS]

Someone on Moped Army has kindly done a makeover on it for me to improve its looks.

 

[soundwave]

Motor Diameter: 10.5 Inches
Motor Case Length: 11.25 Inches
Motor Shaft Length End to End: 12.25 Inches
Motor Type: Brushless Permanent Magnet
Brushes: No
Weight: 150 lbs.
Max Voltage Input: 360 Volts
Integrated Sensors: Encoder, temperature
Peak Torque: 280 Lb Ft Peak (w/150kW controller)
Peak Power: 210 HP Peak (w/150kW controller)
Max RPM: 10,000
Drive End Shaft: 32 spline 35.5 mm
Thermal Cooling: Internal oil pump with water heat exchange
Warranty Period:1 Year

 

[guerney]

Someone on Moped Army has kindly done a makeover on it for me to improve its looks.

View attachment 56664

Why abandon the hiviz advantage of white gloss? I reckon shiny and highly reflective silver would make for a brutalist cool hiviz shape, to stand out against tarmac, and all those many irrationally tarmac hued vehicles. Corroded green coper plating, not so much, and I fear it'd be stolen faster looking like it's been cast in gold.