I apologize for the late reply. Here is the list of parts that we discussed for the drivetrain:
20mm axle adapter - FWM-ADAPTER20
freewheel - FWM-205
hardware - HDW-200
axle sprocket - SPR-B48F
motor sprocket - CTE-24364
All of these parts are available on the Bicycle Chain Sprockets page. I checked and they were all in stock.
Our chain length calculator is showing a 55.3 link #410 chain for the conversion, however, I recommend getting a longer chain and to break it down to the right size after wrapping it around the sprockets to make sure that it is the right size. Our #410 chain is available on our #410 (1/2" x 1/8") Bicycle Chain page.
I will start working on the product page for the throttle and reply again with a link to it as soon as it is ready.
This link will take you to the place on the page where the FWM-205 sprocket is: https://electricscooterparts.com/bicyclesprockets.html#5-hole-freewheels
In your photo, it looks like the axle sprocket hub is on the left side of the sprocket which would make it require right hand threads. The photo is fairly dark by the axle sprocket though so maybe I am not seeing it clearly. If the sprocket hub is on the right side then an axle adapter and freewheel with left hand threads would be needed. All of the parts that I listed above are with right hand threads. We can special order the axle adapter with left hand threads if needed.
I can see the hub and sprocket better now and the hub is on the left side of the sprocket. With that configuration, the freewheel and axle adapter with right hand threads are needed.
The four-wire THR-65 will replace the original 5-wire throttle because its two black wires are both ground wires and one of them is redundant and not needed.
The THR-65 has a 64-inch long cable. If you need the cable to be longer then we sell Throttle Extension Cables for that.
11 and 44 tooth sprockets will work, however, they will provide a 25% higher gear ratio and 25% less torque than 9 and 48 tooth sprockets will.
With 11 and 44 tooth sprockets the top speed calculates to 4.85 MPH and with the 9 and 48 tooth sprockets the top speed calculates to 3.64 MPH. So the 9 and 48 tooth will provide around 25% more torque at the rear wheels than the 11 and 44 tooth sprockets will. A 350 Watt motor is not that big for a beach cart or wagon that will be used in the sand so the lower the gear ratio is the easier it will move through the sand.
Yeah, our 24V 350W gear motors are 420 RPM however the gear motor on the Razor Dirt Quad is 500 RPM. Razor had to order their 350W gear motors with a higher RPM than ours to be able to get the quad to go 10 MPH.
That is nothing to worry about. Those type of motors do make some noise when they are running because of the two spur gears that are inside of their gearbox. Once the wagon is outside and on the ground, the noise of the motor should not appear to be as loud as it is on the test bench though.