Gearbox Ratio

[Deleted Member 4613]

Does anyone know the gearbox trans ratio on these new Chinese belt drive
equipped kits? Is it 4:1 or 5:1? No info in the descriptions of these
4 stroke kits. I believe the drive sprocket is 10 tooth. That's all I know.

New 4-Stroke 53cc Bicycle Bike Petrol Gas Engines Motor Kit Set 45km/h Scooter | eBay

Find many great new & used options and get the best deals for New 4-Stroke 53cc Bicycle Bike Petrol Gas Engines Motor Kit Set 45km/h Scooter at the best online prices at eBay! Free shipping for many products!

www.ebay.com

 

[Sidewinder Jerry]

Do you already have the kit? If yes simply measure the diameter of each pulley then it's just simple math. If you don't have the kit yet the issues you'll have with it will end up costing you more than if you'd simply bought a 4G kit. With this kit you'll know exactly what the ratio is.

Though they're currently out of 4 stroke kits; it be worth the wait for it.

4 Stroke Kit Installation

www.bicycle-engines.com

 

[Deleted Member 4613]

I don't have the kit, that's why I'm asking so I can
make some calculations of speed when I know the
gear ratio.

 

[Sidewinder Jerry]

I don't have the kit, that's why I'm asking so I can
make some calculations of speed when I know the
gear ratio.

You can always contact the seller and ask them. Seems a few others have similar kits. You could ask one of them if the seller in this particular ad doesn't know.

 

[Deleted Member 4613]

Most of these sellers just sell kits in boxes and don't really know much
about the kits, except for what the manufacturer tells them. I wrote to
a seller and waiting for an answer.

 

[Sidewinder Jerry]

With the 53 cc 4 strokes max hp rpm is around 6800 for around 2 hp. Generally 2 hp at best will get you around 35 mph on 26" wheels.

 

[Sidewinder Jerry]

On 26" wheels, you'd need a total reduction of 15:1 to obtain 35 mph at 6800 rpm. That is around the minimum reduction you can take these engines for level ground use only. Even then the rider and bike is going to have be under 225 lbs total weight.

 

[Deleted Member 4613]

I do have a goal. I intend to go with the 53cc and then boost its power
like I did with my 49cc Huasheng which worked like a charm, by opening
fuel jet to 0.026, drilling holes in the air filter cover and using a 7/8
inch exhaust, all of which boosted the power about 15%. With more
power, I could probably bring down the rear sprocket to 41 teeth
for more speed, and maybe have enough top speed and low end
torque. It's all flat ground where I live. I would like to confirm
my top speed with a calculation once I know the gearbox rato.

 

[Deleted Member 4613]

Here's a calculation that could produce 35 mph:

41 rear sprocket
11 tooth drive sprocket
4:1 gearbox
Speed = 6,800/4 x 41/11 x 6.78x 60, all divided by 5280 = 6800/14.9 x 6.78 x 60 divided by 5280= 35.16 mph
I'm sure this looks like gobly-gook, but that the calculation, showing I would need a 41 tooth rear sprocket,
a 4:1 gearbox, and an 11 tooth drive sprocket to get to 35mph at 6800 rpm. Maybe it's too much to
hope for.

 

[Sidewinder Jerry]

Speed (mph) = rpm ÷ total reduction × wheel diameter × ⚻ ÷ 1056.

6800 ÷ (4 × 41/11) × wd (?) × ⚻ ÷ 1056 = mph