It seems like 4-stroke bike engines transmissions are ever-changing- you never know what style of transmission you're going to get. Grubee's, for example, used to come with figure-8-shaped transmissions that required oil, then they changed it to a transmission that only requires a bit of grease. These days most 49cc 4-stroke bicycle engine kits come with only two styles of transmission: single chain transmissions and dual chain transmissions.
Older 4-strokes were run off gear-on-gear transmissions: transmissions that used two gears that ran off of each other to turn the driveshaft and clutch shaft. But now transmissions use a chain
to connect the driveshaft and clutch shaft to move the engine. Some transmissions use a single chain to do this, while other bikes (like the Flying Horse 5G 4 Stroke Bicycle Engine Kit
) use a dual chain.
So what does this all mean? It means that depending on the style of transmission you're using, you might experience some issues between the two. Let's show you what we mean:
Fitting an engine to a bike can be tricky, especially when you're working with a 4-stroke. Single chain transmissions tend to have smaller internal transmission gears, so the cases don't need to be too wide. These style transmissions usually don't require much modification to fit on your bike- just a simple bolt-on operation.
Dual chain transmissions, though, tend to have bigger internal transmission gears, so their cases are often bigger than others. Because of the size, these transmissions often require riders to swap out their cranks
to pedal the bicycle.
We all want a transmission that pulls, and most 4-strokes have better torque than their 2-stroke counterparts. But the size ratio of your transmission gears makes all the difference when pulling your bike.
Single speed transmissions have a small gear ratio from its rear clutch sprocket and the drive shaft sprocket, which works well on downhill and flatland roads because lower gear ratios are necessary for getting good land speed- just like a bicycle's gear ratio. But like a bike, that small gear ratio's going to make it hard to go up hills.
Dual chain transmissions have a higher gear ratio, which makes engines like the Flying Horse 5G 4-Stroke perfect for going up hills. With a lower ratio you may not be able to get up a hill without burning the motor out, but with a higher gear ratio (and sometimes a little pedaling) hills aren't a problem. You won't lose as much speed going up hills as you will with a smaller gear ratio.
No chain means no movement, and with a single chain transmission, you might have just that. Because they're asked to pull a lot of weight behind them a single chain may need constant repair. Most single chain transmissions are asked to take it easy on the throttle, especially when going up hills and during take-off, so they unintentionally might make your bike a little slower.
On the other hand, dual chain transmission chains are reinforced. This allows you to hit the throttle on a hill or when you start the engine and the transmission will be able to handle the force being applied.
Throttle Response and Longevity
4-Stroke bike motors idle by letting the transmission chain and sprockets turn while the clutch flyweight
stays in place. Single chain transmissions have a welded sprocket that mounts to the clutch shaft, which will give you a relatively quick throttle response. This is great when going down hills or on flat land because the throttle kicks in almost instantly and will keep the bike constantly moving to pick up speed. However, the bearings and sprocket do not allow for a smooth ride, which will eventually snap the chain and can even damage the transmission gears from being so rough.
Dual chain transmissions have a clutch sprocket that has a single-speed freewheel
on it, just like the kind you find on a BMX bike. And in the same way, when you stop moving the bike forward, it will idle smoothly, giving you a smooth ride. Although the throttle response is slightly lower than the other, there is more room to work with on these style transmissions, so the gears and shafts can relax a little more.
At BikeBerry, we like to offer Flying Horse 5G 4-Stroke engines with dual chain transmissions because our riders like to climb hills, but are they necessarily better? We think so, but other riders (like those in flat states) would rather choose a transmission that won't make them change their cranks. Whichever transmission you choose, make sure that it pairs perfectly with your bike and your riding style. Trust us, there's nothing worse than being halfway home and your transmission giving out. Nothing