Experimenting With A Hybrid Minibike

Added: 2026-05-13

[00:00:00]Hello everyone. In this video, I'm going to take this minibike with a running gas engine and install an electric motor to work together with it. This is more of an experimental build, and it didn't go quite as planned, but I thought I'd make this video anyways to show it off because I think it was kind of interesting. Now, calling this thing a miniike is kind of misleading. It's really a miniike in design only. It's actually quite big. Check out the tires compared to the rear tires on my YFC 450. They're way bigger. Before I saw this bike for sale, I hadn't seen any bikes like this before. So, I did a little bit of research and it turns out this bike is super old. They were made in the 70s. The bike I bought definitely isn't original since it has a Predator 212 engine, but that's probably close enough to the engine that it had back in the day. Now, compared to all the electric bikes I'm used to right now, riding this bike is not a very good experience. It feels like the engine is just roaring and vibrating like crazy, and the bike is barely moving. The bike feels slow because of how big it is and how big the tires are. Having to spin all that mass up to speed definitely takes a bunch of extra power. After this first ride, I also realized why it was vibrating so much. The engine mounts are horrible. As you can see, the engine is bouncing back and forth so bad that it's actually hitting the torque converter pulley on the frame and sparking. While doing this test, I also realized that at max RPM, the rear tire is actually ballooning out and doing a burnout on the fender. So, that's not good. I think it's about time I start taking this thing apart and fixing it. I didn't notice at first, but the motor is actually spaced up on four nuts. This is definitely not helping the vibration problem. Once I chopped off that stock motor mount piece, you can see just how thin this is. It's definitely not strong enough for something like this. Now that I have a blank slate to work with, it's time to introduce some of the electrical components. Here we have a 55 amp controller and a QS90 motor from this electric winch project that I never ended up doing. I don't have a battery to go with this motor and controller, so I'm going to make one real quick. I picked up some of these LIF P4 cells that are 15 amp hours. Once I put 24 in series, it should work pretty well.

[00:02:09]Here's the configuration I decided on.

[00:02:12]Assembling them like this should have it fit perfectly where the original gas tank was on the mini bike. The first thing I did was attach all the cells together with some thick double-sided tape. This should hold the structure and make sure the cells never touch on each other and short out. Next, I determined how I was going to connect the cells together. I had some.5 mm thick copper, so I decided to use that. But when I soldered it on, it started to melt this little plastic piece around the terminals. I wanted to make sure this wasn't going to be an issue. So, I took one of the extra cells I had and drilled out the terminals and totally removed the plastic piece. After doing this, I tried to push the terminals sideways to short them into the case, but they were still locked into place. So, I don't think it's going to be a big issue if I melt that plastic piece a little bit. I went ahead and added some fish paper on the ends of the cells between the terminals to make sure the copper doesn't short out on that side. I then added the rest of the copper connections and the balance wires. After that, I flipped it over and did the other side.

[00:03:10]After I cut out every single one of these pieces of copper, I have to spend some time bending it perfectly flat.

[00:03:15]Another way to do this would be to just use copper braid like that. So, you could skip that whole process. I'm assuming it would also make soldering the cells easier because you would need a lot less heat. After all the soldering was done, I checked the balance wires, then plugged them into the BMS and set all the settings. Now, it's time to put some double-sided tape on each piece of copper and then put a plastic sheet on it. After this, you already know what's next. It's time for some fish paper and electrical tape on all the corners. then some capped on tape and then finally some shrink wrap and hot glue. With the battery complete, I decided to attach the motor to the engine. Next, here's how I did it. I just took two flat pieces of steel and went from the torque converter mounting points on the engine over to the front cover bolts on the motor and then put another piece over here in the back mounted to the gas tank mount. After this, it's time to fire the engine up.

[00:04:10]Having the motor bolted onto the engine like this actually makes it a lot more balanced because normally on this engine, it's super heavy on the cylinder side, which means if it's just sitting like this, it'll easily tip over toward the cylinder. Having the motor on there means the center of mass is actually over the balance point for once. To get the motor to mount this close to the engine, I had to cut into the fan shroud a little bit. I also had to cut a big chunk out of this piece. With that piece on, the motor matches the engine really well. It almost looks factory. With that done, it's time to mount this thing to the frame. I just put a piece of wood here real quick since I just chopped off the motor mounts. I already know that I'm going to have to increase the gear ratio since the top speed is going to be way too high with this relatively small sprocket on this giant wheel. I'm going to do this by installing a jack shaft in this open area right here. I decided to upgrade the motor mount from the single sheet of steel that the old one was to multiple pieces of square steel tubing.

[00:05:09]Before I did the final welds, I made sure to drill all the holes and bolt everything up to make sure it all lines up correctly. These mounts should be a lot stronger than the one that was on it. Here's a look at the jack shaft I'm going to use. This should actually solve two problems. One, the gear ratio, and two, the chain being different on the rear sprocket and the motor sprockets.

[00:05:28]Installing a jack shaft like this also lets you slide the motor left and right as much as you want. However, I don't really benefit from that in this case.

[00:05:36]Now, I don't know what I was thinking at this point because when I installed this jack shaft, the two sprockets that were on it are basically the same size. So, the gear ratio is still way too high.

[00:05:46]But luckily for me, I had a much bigger sprocket I could put on the motor side.

[00:05:50]I had to take a big notch out of the frame to get this sprocket to fit. I guess I could have just spaced the bushings up a bit, but I think this will be fine. At this point, I went and test rode the bike and it was working fine besides the throttle. It was so mushy and I had to twist my hand a full 180° to even go full throttle. I ended up ripping the little crimp end off the throttle cable. And after driving the bike back by using this little lever as the throttle, I realized I should just take the governor out of this engine.

[00:06:17]That way, the throttle will feel a lot better to use and the engine can unlock its full potential. Before I made my YouTube channel, I used to work on a bunch of go-karts and minibikes. So, this isn't my first time removing the governor. I already know the strategy.

[00:06:30]The first step is to take the gas tank and the whole intake setup off. After that, I need to take off this side panel, but it's going to be a bit more annoying since I have the motor mounted to it. I just took the side panel off with the motor all in one go. After that, it's time to get this governor arm out. I like to just cut the top off and then slide it down. It's way easier than trying to fiddle with it forever. After that, I installed a bolt with a lock nut to plug that hole and then used some needle-nose pliers to rip out that governor wheel. I then started reassembling everything. And then I realized I didn't have another normal cable throttle. So, I'm going to try and control it with an electric throttle. To do this, I just need to control the little butterfly valve inside the carburetor with a servo. I did this by welding this little piece of metal on.

[00:07:14]Then, I can take the little servo hat piece here and stick it right on. To mount the servo to the carburetor, I took this little piece of metal that already had a convenient rectangle cutout and then drilled some extra holes for the carburetor and the two bolts.

[00:07:28]Now, it can go on just like that and control the butterfly valve. However, now the airbox doesn't fit since it hits the servo. So, I'm going to make that a lot smaller. Here's what I came up with.

[00:07:39]I just chopped the airbox up until it's basically just a 90° adapter and then bolted the air filter straight onto it.

[00:07:45]It even holds the choke lever down so it doesn't fall off. I didn't even mean to do this, so that's a welcome surprise. I went ahead and set the servo to the idle position so I could fire the engine up to make sure it still ran right with the new air filter. But right when the engine fired up, the motor wires started sparking like crazy. I forgot I still had that chain on connecting them. It turns out the motor wires were shorting out on the exhaust enough to melt them a little bit. Now that I know the engine still works, it's time to connect that servo to an electric throttle. I just grabbed an Arduino Nano and then started connecting some wires to read the throttle and to drive the servo. I don't even need any extra circuitry. It's just soldered straight to the Arduino. To generate the analog throttle signal to control the controller, I do need two extra components, a resistor and a capacitor in series between the signal and the ground. To convert the PWM to an analog signal, after that, all I need is power, which I'm getting from the power bank I made in the drone video. Here's a quick look at the code. It's pretty basic.

[00:08:52]After a quick test and slapping everything on the bike, it was time to give it a test ride. And before you say anything, yes, I know running the motor like this with no fan guard on it will cause it to overheat after a while.

[00:09:04]Don't worry, I only rode for about 5 minutes.

[00:09:22]The main feature I wanted out of this build was the ability for the engine to die whenever you didn't need it and then fire right back up when you hit the throttle. And it seems to work perfect.

[00:09:32]However, the throttle is now even worse than before I broke the throttle cable.

[00:09:36]It definitely could be improved a lot by rewriting the program, especially if you could read the RPM of the engine.

[00:09:42]However, I just don't want to go through all that hassle. No matter how you program it, it's always going to have a bit of a delay because that servo just isn't very fast.

[00:10:02]Also, did I mention the brakes are absolutely abysmal? It feels like they're barely doing anything. It's super sketchy with this weird throttle that I'm working with. The brakes on this bike are these tiny drum brakes.

[00:10:14]I'd be surprised if these even worked very well when they are brand new. The funny thing is that's probably as spetos with how old this bike is. Another negative is that I think this motor will definitely overheat being this close to the engine. Having it this close really reduces the cooling capabilities of both the engine and the motor. At least the battery and controller wouldn't overheat since they're in the front being blasted with fresh air. After doing this test ride, I really lost all motivation to work on this project. I had a bunch of ideas of stuff to do where you could take off the rear chain and then run it as a generator with an inverter and power stuff. Or you could run it as just electric or just gas or just have electric kick in on the low end for torque and have gas take over on the high end. But I just have other stuff to do. I really don't want to do this. So, I guess I'll keep this electric stuff to use in a future video. I think a hybrid build could be super awesome. However, doing it like this isn't the best. The gas engine and the electric motor aren't similar enough. So, forcing them to always spin the exact same RPM really limits their capabilities. I think building something like my electric go-kart that also has a gas engine like this with a manual clutch would be super fun to do since you would have the extremely fast acceleration of the electric motor that isn't limited by the centrifugal clutch on the gas engine, but you would also have the added power and noise of the gas engine. Having the gas engine and electric motor separate would also allow you to use each one independently, which would be a very interesting feature that would kind of allow you to have two go-karts in one.

[00:11:45]If you think this would be an interesting build, then let me know. I definitely could make it happen.

[00:11:50]Anyways, that's it for this video. I have multiple other builds in the works, so stay tuned to this channel or check out my Discord for sneak peeks of what I'm working on. Thanks for watching.