Readers & Their Rides: 1979 Yamaha FZR 250 Gets Electrified

1979 Yamaha FZR 250

Over the last few years, we have been happily showcasing the incredible ingenuity that e-bike enthusiasts have shown in building electric bikes. From the random odd bird to the professionally executed examples, we’ve seen some truly wild and innovative and beautiful designs. Most recently we came across this unique electric motorcycle build from a South African reader named Justin Cox. 

Justin started with a 1979 Yamaha FZR 250 that he found in 2013 for a mere $400. It had a blown engine, so to make it rideable, he’d have to at least replace the engine. Justin had a better idea—he wanted to convert it to electric and dubbed it “EVlyn.”

The final piece was a solid piece of aluminum stock that he cut down with a saw, then drilled out to bolt the motor and pinion gear on.

 

He started tearing down the bike, finding plenty of broken and stripped bolts along the way, and plenty of dirt and grime everywhere. The gas tank was rusted, so he scrubbed the rust off of it inside and out, even though it would be replaced on the bike just for show.

While he had the bike apart, he tidied up the wiring to go with what he was planning to do.

THE HEART

Replacing the engine with an electric motor was the first order of business. Of all the options on the market, he went with an 11-kW Motenergy DC brushed motor, capable of up to 23-kW peak. He ordered a 72-tooth rear sprocket and a 12-tooth pinion gear to offer a 6:1 ratio. That 12-tooth would later be swapped for a 15-tooth pinion, which lowers the crazy acceleration and ultimately offers 110 kph (68 mph).

To mount the motor pinion, he started with wood to position it and make sure it would clear the swingarm.

 

He first positioned the motor and pinion gear with a placeholder piece he made out of wood to ensure the pinion and chain would clear the swingarm. That worked, so he then remade that piece out of a solid piece of aluminum stock that he cut to size with a jigsaw and then drilled out for the motor mounts and pinion gear.

When prototyping the battery box, Justin used what he jokingly called CAD, which stood for “cardboard-aided design.”

 

THE SOUL

Justin’s original plan was to use industry-standard 18650 lithium-ion batteries. When he started assembling them, there were just too many, and that was going to make it way too expensive, as well as too large.
He’d heard about lithium-titanate (LTO) batteries. 

When he got the battery box back from the engineers he had fabricate it, he bolted it in temporarily and realized his dream was actually coming true. It went to a paint shop to powdercoat it black.

 

LTO batteries are supposed to be safer and have a life cycle of up to 20,000 charge cycles, which comes out to 54 years’ worth of charging if you use a full charge every day. They are massive; each cell is the size of an aluminum drink can. Interestingly, this comparison would come in handy as Justin started prototyping the battery compartment for the bike.

 

“To start prototyping, Justin used what he affectionately called ‘CAD,’ or ‘cardboard-aided design.’” 

 

Justin had no formal training with electronics, and this was something that could be scary with the amount of electricity needed. Fortunately, he learns quickly and had a friend who was instrumental in helping him with this project. To start the prototyping process, like many other e-moto designers, Justin relied on a CAD design (more affectionately known here as “cardboard-aided design”)! The prototype battery case was originally made out of pizza boxes, duct tape and aluminum cans.

From there he had dimensions to send to a fabricator to make an aluminum case. He had double-checked his measurements down to the millimeter with an actual CAD program. When that came back, he retested the dimensions with the actual cells. His tolerances were too tight to line the case with rubber insulation. He shipped that off to the powder-coater.

ALL THE OTHER

While he waited on that, his batteries and BMS (battery management system) had arrived. He tried to make his own BMS with an Arduino (a small, programmable computer), but that proved unsuccessful, so he went with a 450-amp Alltrax controller, which he mounted on an aluminum plate to act as a heat sink.

There’s a 2-kW charge system for the bike.

 

He balanced all the batteries and connected them to create a battery that puts out 85 volts, using bolt-on busbars that he covered with shrink-wrap and a balancing wire attached to each cell. The whole system puts out a lot of heat, so he has several fans to help cool the BMS and motor.

While waiting on the batteries, he prototyped the battery case from cardboard and used aluminum cans as stand-ins. They were the same dimensions as the batteries.

 

He wired in a solid-state relay that was connected to the kickstand. Even when the system is powered, if the kickstand is down, the throttle won’t respond. This way, if anyone touches the throttle when the kickstand is down, the bike won’t launch forward. This is a real concern with electric motorcycles, because you can’t tell that they’re on because they don’t make any noise.

The final piece was the 2-kW charger, allowing the bike to charge fairly rapidly. It can charge off of their standard 230-volt electricity.

This solid-state relay is connected to the kickstand for safety. When the kickstand is down, the relay prevents the throttle from engaging, so nobody accidentally touches the throttle and launches the bike.

 

This will give you an idea of just how big these 66160 batteries really are!

 

HOLY SAVINGS, BATMAN

Total cost for this build was $400 for the bike, $1250 for the motor and controller kit, and $1700 for the battery. That’s an electric motorcycle for $3350. Even if you ignore the cost of labor, that’s an electric motorcycle for less than the price of many electric bicycles on the market, and nearly $10,000 cheaper than an entry-level, street-legal, OEM electric motorcycle. 

At first he thought he’d use industry-standard 18650 Li-ion cells. This would have taken way too many.

 

Justin did several slow, careful test runs as he finished the bike before opening it up for the real fun rides. He now has the very first electric bike conversion that’s fully licensed in South Africa. He is, as he should be, very proud of what he’s created. Now, what’s next?

The finished battery pack with the cells, busbars, shrink wrap and balance wires all in place.

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