I would like to know where I can find a 100 tooth sprocket for # 25 chain. Since I am having trouble getting a front sprocket smaller than 9 teeth, my only other option is to go larger than 89 teeth on the rear sprocket. The final setup would be 9-100 sprockets for about an 11:1 reduction. Note than it doesn't have to be exactly 100 teeth but anything close to that such as 98, 102.... Also note that the bolt holes need not line up with my E-300s as I can have those drilled. Even a split (2 piece) sprocket would be acceptable.
We can custom make a 100 tooth sprocket for #25 chain with an F4 mounting pattern that fits the Razor E300 freewheel.
Here is a link to our custom sprocket order form page:
It appears there would be some clearance issues with 100 tooth rear sprocket and since I am already at about a 10:1 reduction (9:89 sprockets), adding 10 teeth to the rear is similar to just subtracting 1 from the front. I already have an 8 tooth sprocket but am trying to figure out a way to get it mounted. It does NOT have a D bore on it and the bore in too small to go on the motor shaft. If I had a machinist bore it out and make the D bore, the chain would hit the motor shaft and not rest of the teeth properly. No easy solution to get it to work that I know of.
I wish someone would mass produce these 100 tooth sprockets for # 25 chain. It appears the E300s will accommodate it, perhaps with just a little but of modding to make it fit. Even better would be if someone made a motor with a 2:1 reduction built in but without an offset sprocket, then very little change in the stock sprockets would be needed, perhaps just dropping it from 11 front to 9 front to get it to 40% of the original top speed (6 MPH instead of 15 MPH). That should work well offroad.
Also, I noticed with my low "gearing" 9-89 sprockets that I am getting great mileage. That makes sense cuz to go half the top speed takes about 1/4 of the power but I am only going half as fast so the battery "distance" should (in theory) double. I was seeing about 10 miles on a pair of used 7Ah 12V batteries. I suspect using a pair of properly cycled good quality 9Ah batteries instead, 15 miles per charge would be possible on flat pavement with no strong headwinds. That, at about 7.5 MPH top speed (9-89 sprockets), would take about 2 hours. That is much longer than the advertised "up to 40 minutes" on a single charge. It is actually triple (3 times as long).
I would actually like to get 108 teeth so then with the 9 tooth front, that will be a 12:1 reduction with a top speed of about 6.5 MPH (10 kph) on flat pavement.
We can make a 108 tooth sprocket for #25 chain.
Here is a link to our custom-made sprocket order form page where a price quote for this size sprocket can be requested from: