ElectricScooterParts.com Support Center

I can run some gear ratio calculations to see if that setup will work. I will need a little more information on order to run these calculations.

What is the diameter of the tires?

Will the vehicle be run on flat ground only, or need to climb any hills or inclines?

Approximately how much does the vehicle plus driver weigh?

I ran some gear ratio calculations.

The 47 tooth rear with 13 tooth front sprocket setup using a 350W motor and 9" tire results in an 18.55 MPH top speed. This gearing should be okay if the scooter is used on flat ground, it would not have much torque for climbing hills or grades though.

With a 500 Watt motor the top speed would be the same, maybe a little faster, and the hill climbing ability will be better with the 500 Watt motor than with the 350 Watt motor.

If the scooters will be used off road or for a lot of stop an go driving then the temperature of the motors should be checked for a little while after the sprockets have been changed to make sure they are not running too hot.

The Razor E300's original motor is 250 Watts and has a 7mm x 8mm D-bore where the sprocket mounts. I checked and the largest motor sprocket we have for the original motor is 11 teeth. You mentioned using a 350 Watt and 500 Watt motor and since these are not original motors I do not know what their shaft sizes are where the sprockets mount. In order to figure this out you would need to remove the sprockets and measure the shafts where the sprockets mount onto these motors, also note the shape of the old sprocket bores. The sprocket hole interior diameter dimensions and shapes of most electric scooter motors are shown below.

Once the sprocket hole shape and size have been determined then the sprockets available for that motor can be determined. The motor sprockets that we have available for #25 chain are available here, and for 8mm chain are available here.

The Razor E300 scooter's rear wheel sprocket mounts onto a freewheel so any of the sprockets we carry that mount onto a freewheel can replace the original. I checked and we have sprockets that mount onto freewheels for #25 chain available in sizes between 55 and 89 teeth on this page. We also have sprockets that mount onto freewheels for 8mm chain available in sizes between 44 and 54 teeth on this page.

There are more sprocket size varieties for #25 chain than for 8mm chain so it is most likely that #25 chain would be used. #25 chain is a suitable size to use for 500 Watt motors so you could definitely still use that size.

If you install larger sprockets than the original ones then the chain will need to be longer. We have a chain size calculator that can be used to determine the new chain size when sprockets are changed at this link: http://electricscooterparts.com/chainlengthcalculator.html

Please let us know if you have any questions.

The item # SPR-844 44 tooth sprocket that we sell which fits the Razor E300 scooter is for 8mm chain. In order to use SPR-844 an 8mm chain and 8mm motor sprocket would need to be used along with it.

The smallest sprocket for #25 chain that fits the Razor E300 scooter is our item # SPR-2555 which is a 55 tooth sprocket. This sprocket could be used with a #25 chain and motor sprocket.

Chances are the the item # SPR-813 13 tooth sprocket for 8mm chain will fit the 500 Watt motor but not the 350 Watt motor due to their different shaft sizes. Most 500 Watt motor have an 8.5mm x 10mm double D-shape shaft size and most 350 Watt motors have either a 7mm x 8mm or 8mm x 10mm D-shape shaft size.

Please let us know if you have any questions.

We do not currently have sprockets with more than 11 teeth that will fit the 350 Watt motor. The sprockets that we have with 7mm x 8mm D-bores which will fit the 350 Watt motor are only available for #25 chain. We might have sprockets with more than 11 teeth that will fit the 350 Watt motor in the near future though. This will be adding a lot more motor sprocket sizes to our store later this year.