cleaning the bearings
As you can see in the image above, the bearings can be seen inside the handle when looking from the bottom opening. Dust and debris may build up in this area causing the grinding inside the handle. Using compressed air can blow out any dust particles inde the handle.
lubricating the bearings
Once the dust ahs been removed from the bearings, we can proceed to getting a can of lubricant such as WD40 or bike chain lubricant and spray/apply inside the handle. This should penetrate the first and second set of bearings.
maintanance
Lubricating oil may seep out of the top of the handle. Clean this part and you are all done. After a few sessions the handle will regain the spin back up.