The KTM SX-E 5 is a fully electric 50 SX-sized kids racebike. It’s powered by a 5.0kW peak power electric motor housed in a chromoly frame that is fitted with a fibreglass infused plastic subframe that can be fitted in five different positions to adjust the height of the bike. Along with the adjustable seat height, the SX-E 5 also has six different ride modes that allow you to tone down the power or turn it up to full power mode. The SX-E 5 can suit a wide variety of rider levels and is a great introduction into the electric market. The only real down side to the SX-E 5 is the fact that in order to buy it you either have to rob a bank or remortgage your house.
My son is racing in the 50cc division this year at our local clubs and while he is on a petrol-powered 50cc bike he is always drawn to the electric SX-E 5s he races against, and points them out before mentioning he wants one. While they are nowhere near as popular as the petrol 50cc bikes around the tracks, I anticipate a growth in their popularity and we are already starting to see more and more of them.
As a mechanic who runs a workshop specialising in performance work, it has taken some time for these machines to start trickling through my door. In the beginning, everyone would head to the dealers for warranty and service work, but as these bikes are becoming older and more popular, other workshops are starting to see more and more of them, and we have had to do our research to keep up with the tech to be able to service them. Over the last 12 months we have compiled some info and firsthand knowledge, while also asking SX-E 5 owners what they thought about the bike, and if there are any common problems they have seen.
Electrical Faults and Error Codes
Even motorcycles equipped with petrol engines have high-tech electrical systems. These electrical systems are smart enough to be able to detect faults and give error codes that can be deciphered. The SX-E 5 is no different – it is able to detect system faults with the motor, charging system and even the control board to alert the rider to any issues. The KTM SX-E 5 manual gives you a code list so you can go and check what code you are receiving and how to correct it. Unfortunately, many of these fault codes on the SX-E 5 are brought on by water or moisture getting into electrical components. The battery, motor and control module are all sealed units however in harsh conditions or when pressure washing, water can still make its way into components where it is not welcome and can cause issues. In many cases the water gets into the control module which if dried out in time can be all good, but if left to long will cause corrosion and often lead to parts needing to be replaced to rectify the problem. With all this being said a KTM 50 SX petrol-powered bike is one of the highest-maintenance motorcycles ever built, and plenty of examples often blow stators due to water and corrosion, so I wouldn’t necessarily say this model is better or worse than the SX-E 5 in the electrical department.
Battery Charging Problems
All of the battery charging problems I have encountered with the SX-E 5 relate back to a dirty connection on the charging cable. These cables need to be clean and dry, especially the electrical connections. I have seen issues from not charging at all to error codes because of mud and water in the charging plug. In one instance, I saw someone who blew the fuse because he tried to charge the SX-E 5 with water in the charge connection, and another who could never get the battery to fully charge in his shed but in my workshop the it would charge completely. In the end we figured there must be an issue with the power source in his shed not being high enough to charge the SX-E 5, and if he charged the bike in his house he had no issues.
Overheating Concerns
Environmental conditions can have a significant impact on the SX-E 5. High temperature days with kids riding the bike at low speeds or in soft terrain where the bike has to work hard will cause the SX-E 5 to run hot. I’ve also noticed that when the batteries are on the way out the SX-E 5 tends to run hotter than normal. It’s also important to remember the SX-E 5 has coolant and it needs to be checked and changed periodically.
Water Ingress Recalls
To my knowledge this recall dates back to the 2021 models as a number of bikes off the production line may have been missing a battery vent valve. If this battery vent valve is missing then water van enter the battery and cause a short circuit. If you have a 2021 model and you are unsure if the recall has been checked and rectified, then contact your local KTM dealer to clarify the bike’s status.
Motor Failures in Wet Conditions
This is usually noticed by the system turning on but the motor not working which is usually followed by a fault code. It is possible for water to enter the electric motor even though it is sealed. I would strongly recommend not washing this bike with a pressure washer as it is possible to push water past the seals, and the water will either cause a short in the motor or corrosion that will eventually lead to a failure. I would also recommend replacing the o-rings and seals on the motor periodically as these motors are expensive to replace.
Throttle Faults
The throttle is electronic on the SX-E 5 and like any other bike it is often the first thing that jams in the mud and dirt in a crash. This can allow water and mud to get into the electronic circuit in the throttle and cause corrosion or shorts. The throttle is something I recommend taking apart and cleaning after any wet-weather riding as any water that sits in there can play havoc. Generally, a throttle fault will not allow the bike to move and will give you a fault code indicating a throttle malfunction.
