Do It In The Dirt — Electric Dirt Bikes Rock

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A visit to Francisco Shi's workshop is always an education. This afternoon he wanted to show me his new electric dirt bike as well as update me on his Pajero conversion project. He had just got back from a ride; the bike was dirty and being charged. He tells me it was a risky buy. He was worried about the range and the weight.

Just back from a ride. Photo courtesy of Majella Waterworth.

As I am very ignorant of dirt bike riding, he patiently explained the issues to me. He had charged the bike to 100% the night before, but found it only had 50% charge when he took it out for a ride. He will explore this issue and no doubt come up with a solution. The Surron Storm Bee weighs about 10 kg more than his 4 stroke Kawasaki KLX 300 (110 kg). He says it feels like the same weight, but he hasn't had to pick it up yet. "Where do they get these names?" he asks.

Although the power and weight are similar, the Surron only has about half the range — 45 km (28 miles). But dirt bikes aren't built for range. The dirt bike uses the same amount of charge on a hard track as it does on an open track. His petrol bike uses a lot less fuel on an open track. On a bush track, Francisco and his friends average about 15 km/h and ride for about 3 hours.

The Surron Storm Bee is imported from China and costs around AU$15,000. An equivalent petrol bike (with double the range) is around AU$17,000. Almost price parity.

Francisco has big plans for the Surron's battery. He expects that he can increase its range by 60% when he upgrades the 4.4 kW battery to 6 kWh using pouch cells. In fact, he would like to have two batteries, so he can swap partway through a ride — loop around, swap over, and keep going. It's a bit of a Gogoro approach. He and his friends ride in the Queensland state forests.

He is looking into batteries with silicon anodes, which could double his capacity.

The bike takes about 4 hours to charge. Francisco will also explore better/faster chargers. The battery that came with the bike weighs 25 kg (25% of the net weight of the bike). His new proposed battery would be lighter.

Storm Bee battery. Photo courtesy of Majella Waterworth.

We walked over to the subframe being fitted with batteries and motors for his Pajero. Francisco has found motors that fit better within the subframe because the gearing is more appropriate — he no longer has to have an "H" shaped battery pack. It is simpler and more efficient. It also means there is a greater possibility of making a kit for DIY enthusiasts to convert their own Pajeros. He already has some in the 4-wheel-driving Pajero community who are interested in doing this. He found the motors in a brochure from his regular supplier when working on his next project.

Motors in Pajero subframe. Photo courtesy of Majella Waterworth.

As we walked back to the bike, he told me: "When I first got it, I didn't know the range. The quoted range is 100 km at 50 km/h on the road." Francisco needed to test range in the bush-bashing dirt bike world. After riding for 48 km, the battery was down to 3%. "So, realistically, the range is about 40–45 km." He expects that on a motocross track, it will do about 30 minutes of riding.

Francisco rides a Hard Enduro. It's not fast, but it is rugged. Many times, you have to ride slow and make your own track. For this style of riding, the low range of the Storm Bee is adequate. It also has regenerative braking.

He has made some modifications to the bike. The tilt sensor, which turns off the motor if the bike tilts, has been removed. Enduro style riding requires being able to tilt the bike to get around objects. He has disconnected the headlights to save power — no, he doesn't ride the bike in the dark. The bike doesn't need the stand drop sensor either. These items are fitted to the bike to enable registration. Bikes must be registered to ride in the state forests of Queensland.

Some features that are fitted for safety actually make the bike more dangerous on a bush track. He has also turned off traction control for this reason. He explains: "Going up a hill in the dirt, it takes skill to allow the back wheel to slip without losing control of the bike. Essentially, leaving the traction control on, you wouldn't get up the hill. You need good balance and throttle control."

"You’ve taken off the training wheels," I joked.

Today was Francisco's 4th ride on the electric dirt bike, the first time with his riding mates. He says they all wanted a turn on the bike, but he didn't have enough charge to share it around. One member of the group already has an electric car. I asked if there were any disparaging comments. No, he said, they are all mature, it is a serious sport. "Where we go, if you break down, you have to walk out. One rider broke his ankle and they had to send in a helicopter to get him to hospital."

So, what are the differences — apart from the obvious quiet?

I will paraphrase. With a petrol engine, you get the right torque at certain revs and a slow response — so you open the throttle to increase the revs, then slip the clutch. When going uphill, 50% of the time you are using the clutch to stay in the power band. You can't change gears on the way up because you would lose momentum. When he first got the bike, he was worried about the driving experience without a clutch, but with an electric bike, you are in the power band all the time. "Point and shoot," he says.

With an electric bike, the torque is available at low speeds — when you need it. With a petrol motor, there is little torque at low revs, so you have to rev up and slip the clutch — for example, if you are going over a log blocking the bush track. In the same situation with the Surron, Francisco opens the throttle to lift the front wheel and the bike goes over. There is no chance of stalling it.

Some other advantages of the electric bike: no hot exhaust pipe to melt the legs of your riding gear; no easily damaged radiator. He says that when the group got to the top of the hill, you could hear the coolant being sucked back into the newly boiled radiators of the petrol bikes. The Surron has a reverse gear. This makes it easier to negotiate a blocked track. There may be rocks behind — the Surron can reverse over these. In the past, Francisco has had to dismount and push the bike backwards.

An electric trail bike has much less maintenance than its petrol counterpart. Francisco would have to clean the filters and top up the coolant after every ride on his Kawasaki and change the oil after 2 or 3 rides. Every 6 months (about 50 hours of riding), he would clean the valves, and each year change the timing chain. It is worse for two-stroke motors — they need new rings and rebore every 6 months.

With the electric bike, Francisco notes that the drive chain and the tryes wear about the same, but the brakes last longer.

By the end of our interview, the bike was charged to 60%. Francisco says that if petrol wasn't so expensive, he would go for another ride. He tows the bike and trailer behind his petrol Pajero. His wife's BYD Atto 3 could tow a trailer, but she won't let him fit a tow bar. The things Francisco tows would make her car dirty, and she likes to keep it clean.

David Waterworth is a retired teacher who divides his time between looking after his grandchildren and trying to make sure they have a planet to live on. He is long on Tesla [NASDAQ:TSLA].

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