My Modifications

Springs, Grips, Pegs, Risers, etc.

Prior to purchasing the bike, I was given the opportunity to ride it for a day at our club's practice grounds.  Overall it worked well for me.  I knew a few simple changes would improve the bike for me substantially.  

The thing that bugged me most was the rear brake pedal – too far inboard and too high.  But that's not a problem unique to the EM, I had to extend the pedal tip 20mm outboard on my OSSAs too.

Next were the suspension springs.  The prior owner is a big guy and had installed stiffer springs at both ends.  Fortunately, that's an easy swap to return to standard.  There's only one spring in the front, and the rear does not require a spring compressor.  While things were apart, I took the opportunity to lube the suspension pivots and Anti-Sieze some fasteners.  I set the spring preloads at their minimums based on experience with other trials bikes.  I left the rebound clickers set at standard as that seemed a reasonable starting place for the initial testing.  After the next evaluation ride, I fully opened the “end of stroke” valve at the bottom of the left fork leg.  This took some of the harshness out of the last 25 mm of travel.  Unfortunately, I forgot to install the customary fork travel O-ring and ended up with a zip-tie.

The bike did not turn as well as I expected so I slid the fork tubes up in the triples about 6 mm.  This resulted in 10 mm being exposed above the top clamp.  The effect of all these changes left an already low skidplate with even less ground clearance.  In fact, the lean angle for the side stand was now quite precarious.  For me, the only real use for a side stand is moving bikes around in the garage, so I may eventually remove it completely.  I suppose some lighter suspension springs may be in the bike's future too.

Mostly for comfort, I installed my favorite Jitsie Grip footpegs.  These are wider and “grippier” than stock.  Likewise, the stock handgrips were swapped for softer and larger-diameter Progrip 699s.  These are streetbike grips that I use on everything (although not without modification on trials bikes).  Finally, I machined some homemade bar-end sliders out of acetyl plastic with retention hardware copied from Enduro Engineering's Bark Busters.  This helps ensure I won't scrape my hands on trees and the throttle won't stick open if I plant that bar-end in the dirt.

Most of my other trials bikes needed bar risers for comfort.  The ePure Race seemed comfortable without them, but Cindy convinced me to try them.  So I raised the bars 16 mm and do like it better.  Strangely, it also seemed to steer better – or at least more familiarly.

Unsurprisingly, the levers required some repositioning and adjustment to suit me.  I also removed the LED lights along with their DC-DC converter (which makes 12 volts out of battery voltage) and the associated wiring.  This simplified the wiring ever so slightly and removed that source of battery drain.

Coulomb Counter

I purchased a DROK coulomb counter via Amazon for about $31.  It is intended to give a real-time display of voltage, current, instantaneous power, and total watt-hours. 

But I don't care for it at all.  About the only good thing is that it has a Hall effect current transducer.  Thus, it was a simple matter to install this transducer on a battery cable by temporarily removing a pin from the Anderson connector.

2023 Modifications

Below is a summary of modifications made as I gained experience with the bike.   Most are discussed in detail elsewhere.

• Installed a softer fork spring.  Tech sells three different progressive springs.  Besides standard, they offer one softer and one stiffer.  As a lightweight rider, I immediately benefited from this change.   However, the standard rear spring is working well for me as I tend to land primarily on the rear.  

• Installed an adjustable fork compression damping valve.  Again, of extra benefit to a lightweight rider.  This is mostly for comfort.

• Increased rear spring preload.  This had a profound effect on how well the bike turned.  I found raising the fork tubes in the triple clamps insufficient.  Increasing the rear preload tends to tip the bike on its nose and aids in turning.  However, taken too far, it can adversely affect front ground-clearance and jumping ability.

• Made a tungsten-copper flywheel weight.  I felt sure I would appreciate more motor inertia.  It was a large amount of work, but well worth it!

• Configured controller's regeneration input to provide a small constant “engine braking” effect off-throttle.  This yields a more familiar feel - something akin to an ICE bike in 3rd gear.  A small positive side-effect is that it yields about a 1% increase in range.

• Robust battery side covers.  I can't take credit for this one, it was done by the prior owner.  There is a section describing them in detail. 

2024 Modifications

After much testing, I started the 2024 season with modifications that provided the best compromise performance. 

• Re-installed lanyard kill switch.  As much as I dislike wearing a lanyard, I decided it was in the best interests of safety to do so.  I've given many people the opportunity to try the bike, and it just seems like a wise precaution.  It also somewhat acts as a key.  I suppose my ultimate solution would be a tip-over kill switch as implemented on street bikes and the Montesa 4RT.

• Settled on a regen solution.  The lanyard kill switch got in the way of my preferred regen solution (a bicycle thumb throttle).  I've gone to a fixed 1-volt regen implemented with a potentiometer.  This gives a desirable amount of regen braking on closed-throttle that emulates an ICE bike.  See the section titled Regn Experiments to read all about it.

• Shorter gearing.  Installed a 10T front sprocket from the 2024 Comp model.  A detailed discussion can be found in the section titled Mechanicals.