The Microstar can certainly profit from relubing certain areas. Here are a few lube points that can be easily done. I use a synthetic oil with an extension needle-tube on the end, one of these:
https://www.ebay.com/itm/LARGE-2-oz-Liquid-Bearings-with-EXTRA-LONG-3-needle-BEST-100-synthetic-oil/230963683534?epid=1554654191&hash=item35c68220ce:g:6OkAAOSwfztbURIi:rk:3:pf:1&frcectupt=true
I originally got it for clocks, but it seems like good oil, and the extensions are handy.
Places to clean and lube to fix jerky focusing:
1. With the scope right-side up, remove the top plate (5 screws under covers); you can then raise and lower the inner movable casting that holds the nosepiece turret with your fingers.
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Do not drop the turret after raising it! The inner casting (holding the turret) rides up and down on a cam affixed to the focusing shaft (you can see the cam if you peer down past the neutral-density filter when the scope is upside down). The plastic/resin cam is fragile (the repair of which is my next post) and can be broken if the inner casting is raised and dropped too hard, or if the microscope is dropped; the ball-bearing cam-follower will apparently just punch right through the cam surface:
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You can see two guide ball-bearings, one on the left (fixed) and one on the right (spring-loaded). Check the outer race surfaces of these bearings as you raise and lower the turret. I've seen these bearing races broken or flat on the outer race, necessitating buying new bearings (they are a standard size, so available). Also the surface of the inner casting, where these small ball-bearings bear, might need swabbing with a q-tip w/ solvent (I recommend naphtha), to prevent a gritty feel if dirty. Oil the ball-bearings (they seem to be just shielded, not sealed); check them for excessive play, they shouldn't wobble sideways at all.
2. Go to the rear of the inner casting, and you can oil the shaft and drip some oil into the entry points of the upper linear bearing (it's not just a plastic bushing).
Flip the scope upside down, and lube the lower linear bearing (which is now above the other one) the same way. This is where the extension tube comes in handy. Also oil the cam-follower ball-bearing, accessible with the extension tube, from back near the lamp. Try not to over-oil, excess oil might run all over the cam.
3. Sometimes there is grit on, or a rough surface to, the cam surface that causes a bumpyness when focussing; inspect the cam surface and clean or polish if necessary.
Cam breakage or a messed-up cam surface is for a future post, and is not difficult to fix, but requires removing all of the focus gear, etc., and extracting the cam. Hopefully you don't have any of that. It is common to see, on bottom-dollar Microstar carcasses, messed up cams, missing filter holders, broken bearings, etc.
