Recently bought a used Tao Tao 110, there is a vibration noise at hi speeds. Could this possible be a bearing issue or something else? Has anyone added a zerk fitting to rear axle housing?

 

Check your chain for tightness. I have found the import sprockets are not 100% true. So if you tightened the chain on the slack side then when you hit the tight side you will feel every link in the chain until it hits the slack side again

 

I will check that, thanks for the advice.