EM 5.7

Acquisition

A confluence of circumstances caused us to buy a used Electric Motion 5.7 in September of 2021: Cindy got tired of kickstarting her Sherco 200, I wanted to experiment with electric vehicle technology and a nice one came up for sale.   

We drove 1600 miles, one way, to buy the bike.  It was 100 degrees in Texas when we arrived.  The best thing about the trip was that it was easy to lay the bike on its side in the back of an SUV - no need to tow a trailer.  I would not have wanted to do that with a used ICE motorcycle without a lot of prep/draining of fluids.

 EM 5.7 Specifications

I could not find any official specifications published by EM for the 5.7 models.  The following was compiled via internet searches.

Top Speed: 55 kph (34 mph).  

Battery: 48-volt, 25 Ah lithium-polymer which stores 1.2 kWh (thirteen nominally 3.7-volt cells in series). 

Ride Time: 60 to 160 minutes.

Weight: On my scales, the bike weighs about 166 pounds (75.5 kg) and is very front-heavy.  Sadly, the 70 kg (154 pounds) spec I found prior to purchase was incorrect.  It was for the EM 5.7 “Sport.”  That version came with a smaller 16 Ah battery and superior/lighter forks.  I think it was probably a first attempt at making something suitable for competition.  I suspect the intention was for the rider to have a spare battery or two.

Motor: Brushless DC, 5 kW nominal, 10 kW peak made by Golden Motor in China.  

Motor Controller: Kelly KEB48601.  This is an inexpensive ($300) Chinese controller with freely-available configuration software.  It has a 140A continuous current rating and is good for 340A for 30 seconds.  It can withstand up to 60 VDC and weighs a bit over 4 pounds. 

Power Modes: Novice, Trek, Trial (Wet), Trial (Dry).  

US MSRP: $7600 in 2013 (the year the 5.7 was introduced).

Finally, what does “5.7” mean?  Originally, I assumed it meant 5.7 kW, but since the French use a comma as a decimal separator that now seems unlikely.  A very early brochure indicates that the initial (13-cell) battery is rated for 5kW continuous and 7kW peak.  So even though the motor may withstand 10kW peaks, the real power limitation is the battery (or more precisely the BMS, as that is what's actually performing the limiting). 

Early Riding Impressions

Cindy immediately liked the EM as well as her Sherco 200, even though it is quite different to ride.  She thought the differences would improve her riding.  I found that to be true when I got my 4-stroke Montesa as it forces (allows?) you to learn different techniques.  Cindy found the 5.7 to climb “her size” slopes better than the Sherco.  It was equally adept at bumping over logs, but good rider positioning was critical, otherwise, it stopped dead.  Riding at slow speeds and pausing requires better balance.  She found not having to kickstart it a joy!

The bike has a high center of gravity.  The skidplate is 1.25 inches higher than Cindy's Sherco.  The “seat” is 2 inches higher.

We both found the regenerative braking button awkward to use if you also have one finger on the clutch lever.  This was the first thing I planned to fix.

One of the bigger disadvantages I can see with the clutchless EM is not being able to blip the throttle.  I do that frequently at very slow speeds to help keep my balance.

For me, the hardest thing about riding a trials bike without a mechanical clutch is how to generate lift without velocity.

One of the maintenance advantages of the EM5.7 is the availability of parts from other than the normal dealer network.

Vibration-less running is spooky and very pleasant!

Because there is no “neutral” the bike requires more effort to push than something with a gearbox.  No problem in the garage, but a real PITA if you actually must move it any distance.  Parking on a slope is a problem because there's no way to “leave the bike in gear” so it can't roll away.

Although not silent, it is much quieter than an ICE trials bike – especially at large throttle openings.  After listening to various electric motorcycles in videos, I did not care for the sound.  But it is not fatiguing and I quickly became accustomed to it.

The front forks are lightly sprung (which is probably okay for us lightweight riders) but my initial feeling was that there was insufficient compression damping.

I had great difficulty jumping logs with it.  I tend to use the clutch to “shut off” after cresting a log.  This thing just stops dead.  I expect my idea for a progressive electronic clutch will help.

It does not turn tightly.  The steering geometry seems wrong.  The front wheel “pushes” (slides out) in sand.  I will try moving the forks up in the triple clamps.

The rear wheel can easily lose traction.  The motor controller runs in “torque” mode.  This can cause a rapid increase in wheel speed if the load is removed (i.e., getting air).  The controller can also run in “speed” mode, but I don't think that would be appropriate at all.  There is a “balanced” mode that presumably melds both torque and speed.  I tried it and found it to be unpredictable – not at all suitable for trials.  I quickly returned it to torque mode.

Although it climbs simple hills well, I failed badly on more difficult loose climbs.  This was partly because you can't “blast off” at the bottom of the hill with a clutch dump and gain momentum early.

I definitely did not want to even attempt my most difficult obstacles with it.  Of all the trials bikes I've ever ridden, the EM 5.7 is the one I feel least confident on.

When coasting (zero throttle) down a long downhill, if you open the throttle slightly it slows down (that's a weird feeling).

Overall, my initial impression was that I can improve it quite a bit.

Power Modes

The four power modes are selected via a 3-position rotary switch in a box located above the battery.  These positions are labeled, “Novice, Trek, and Trial.” Novice is completely useless.  Presumably, it's intended for someone with very little motorcycling experience.  Trek is slightly better, but I can't see ever using it.  That leaves Trial which is further modified by a typical handlebar “map” switch.  Map 1 (wet) is the small rocker button and Map 2 (dry) is the larger button.  I remember it as the big button for big power.

Eventually, I'll remove the 3-position rotary switch box entirely.  I may relocate the map switch out of the way to clean up the handlebars.  My Montesa 4RT has a similar switch that I removed, which permanently selected the high-power setting (as we don't care to ride in the wet anyway.)

Trails versus Trials

I must say the 5.7 is really in its element ripping down the loop trail.  That extra half-inch of soft suspension is a plus.  It's surprisingly comfortable for a trials bike.  The lack of vibration and noise is very appealing.  It's also nice not to have to shift (trials bikes are meant to be difficult to shift to prevent inadvertently doing so).  I find myself going faster down the loop trail than I normally would (which is probably a bad thing).  But it's pretty easy to top it out, and I have doubts about the claimed 34 mph top speed – at least after the battery is somewhat depleted.  I'll probably fit a bicycle speedometer to see what's happening.

One-Year Update

As of this writing, Cindy has owned her 5.7 for a bit over a year.  She's quite happy with it – especially since my last improvement to regenerative braking.  She gave me the highest possible compliment saying, “You've made a motorcycle out of it!”

Cost of Electricity

In one year of ownership, the total electricity cost has been just $6.58 (based on a rate of 16.8 cents per kW-hour).  This amounts to about 57 outings and about 50 charges.  A few of those charges were part of battery capacity testing.

I kept a spreadsheet of energy replenished on the DC side over the year.  The battery has accepted approximately 34 kWh on the DC side.  By also recording the AC-side energy consumption, I calculated the charger is about 87% efficient.