Dual Chain Transmissions Vs. Single Chain Transmissions: Do You Know What's Driving Your 4-Stroke?
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 transmisson-temp1Fitting 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. Torque transmisson-temp2We 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. Chain Strength transmisson-temp3No 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 transmisson-temp4 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.

5 comments

Marvin Harvey

I have had to replace 3 magneto loops and now another one went bad…I ordered an extra one so I can replace it. What the #&@*" is going on?

BikeBerry

“Good afternoon, Marvin! If your magnetos keep shorting you could have one of a few things:
1. The way it’s wired to the kill switch and CDI is somehow creating a short, which is taking out the magneto
2. If there’s moisture build up around the engine (for example, if you ride in cold weather and bring the motor in to a warm area, causing condensation around the engine), some of that water could have gotten on to the magneto, causing a short
3. Some newer magnetos have a thin layer of resin on them, which- if not scraped off before installation- can melt, effecting the wiring on that magneto, causing a short”

gary

I am in the planning stage of a Rear engine 4 stroke men’s mountain bike build-are your only two motor choices the 38cc & the 49cc. ??-Doyo ever get in one of the Rear chain drive conversion kits to change it from Friction on the fear tire wish me luck yall!!

Mike

“Hey I bought a single chain gearbox off BikeBerry a good while ago and the single chain is stretched I was wonder if you could tell me the size type chain that fits on there and if you sell it
Thanks”

BikeBerry

“Hey Mike.

We got you covered! We do see the <a href=""https://www.BikeBerry/2-stroke-gas-motorized-mini-dirt-pit-bike-drive-chain.html#product_tabs_description_tabbed"" target=""_blank"" rel=""noopener noreferrer nofollow"">4-Stroke Transmission Chain. This will be all you will need for the replacement."

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