Rear chain adjustment for Razor MX electric bikes.
Razor MX Chain Adjustment
If you have upgraded your Razor MX motor then you probably have discovered that your chain is no longer straight and needs adjusted. A lot of people complain about the chain jumping off the sprocket. This is pretty dangerous, especially if you have upgraded your voltage. My sons bike is going over 30 mph after his upgrade and I didn’t want him to loose his chain at a high speed.
Most aftermarket motors for the Razor MX bikes are the same size for the housing, but the output shaft varies in length. See photo below.
What You’ll Need
- Angle grinder with grinding wheel (rough sand paper or a file can be used as an alternative)
- Vice or plyers
The Fix
I’ve read a lot people trying to modify the rear sprocket. This is harder than it seems because of the design of the rear hub. Its not something you can just shim out with washers. You can also modify the output shaft but this is also not an easy undertaking because you will need to make the sprocket closer to the motor. This is a keyed sprocket design so I wouldn’t recommend modify this part. The best way is to modify the wheel spacer. You can easily shave off a small portion of the spacer to move the wheel into better alignment. You will need to add a washer to the opposite (left) hand side along the wheel spacer to make up whatever material you shaved off on the opposite wheel spacer. This will require you to adjust your rear brake but there is a built in adjustment screw so you will have plenty of room to move the rear caliper over.
Results
This fixed the chain alignment issue. The wheel is still square with the bike and in perfect alignment. The axel sets the alignment and everything works great. I’ve upgraded the rear brake and it doesn’t have the built in adjustment like the stock brake. It still works and fits perfectly. I’ll write an article about updating the brakes in a future article.
