Older trackball mice use rollers and mechanical insides and over several years the ball can get slow and sticky. Luckily you can restore proper function to your mouse through these steps.
The mouse I will be using for this is a Microsoft Intellimouse Trackball from 1998. This tutorial will work for any other trackball mouse that is made before ~2004. Most made after that don't use the same sort of mechanism.
Step 1: Find and Turn Retainer Ring
When you look at the top of the mouse were the ball is, you will see a ring surrounding the ball. This ring is what keeps the mouse from falling out when you turn it.
You can see a small notch or dot on the ring and one that lines up with it on the body.
Turn the ring counter-clockwise as far as it will turn. The notch on the ring will then be about 30-90 degrees from the notch on the body.
Step 2: Remove the Ball and Ring
You can now turn the mouse over and the ball and ring will fall out. Keep them off to the side for later.
If it does not fall out, tap the ring and ball while its upside down, and make sure the ring is all the way turned.
Step 3: Clean the Main Rollers
When you look down into the hole were the ball was, you will see 2 rollers like in the picture. One of the rollers transfer the ball movement into and electronic signal. The rollers are in contact with the ball so over several years they will get dirty and stop moving properly. This will make the ball hard to turn, and the mouse will track badly.
Take a wooden pencil with a very solid pink eraser. The really cheep ones that have stiff pink erasers on them work best. If you use one with a crumbly eraser you will do more harm then good.
Use the eraser to clean off the roller (the black part of it) by moving the eraser from side to side on it while turning the roller with your finger. The roller in the picture has been recently cleaned so its nice and black but yours will be grey and nasty
Do this for each roller then turn the mouse upside down and tap it to get all the dust and lint out.
Important Note: The rollers can be kind of delicate so take care while cleaning them.
Step 4: Clean Strings and Lint Wrapped Around Axles
You will see on each side of the black rollers there are thin metal axles. They tend to get strings, hairs, and lint wrapped around them.
Take a small tweezers and very carefully pick all the lint and strings off of them. The axles are very thin and can be easily bent so be very very gentle. There will also be a small wire spring on each side so be careful not to touch that.
Again the one in the picture is clean, but yours will have a good sized glob of dirt around it.
After you do that, turn the mouse over and tap it to get the lint out.
Step 5: Clean and Lubricate Bearings
You will see small balls were the trackball sits. In the picture they are red, but some may be silver. There will usually be 4 or 5 of these. They don't actually spin, but they are contact points that the ball moves on so they get very dirty and make the ball hard to move.
Do not remove the balls, If you take them out you will lose them, and its impossible to find replacements for those things.
Use your fingers or a Q tip to wipe of the dirt from around the bearing.
Rub a very small amount of Vaseline on each ball. This will make the ball spin nice and free. Its important to not get any on the rollers or other parts of the mouse as it will keep the main ball from turning the rollers. This is also why its important to apply a very small amount.
Tip: If you have no Vaseline, take a "Chapstick" and rub a bit on your finger, then apply it to the balls the same way you would the Vaseline.
Step 6: Cleaning the Main Ball
The main ball is the one you move to make the mouse on the screen move. Because you are touching it all the time, it will get skin oils, and dead skin flakes on it.
Take the ball and wash it under the hottest water that will come out of your faucet.
Dry the ball off with a cloth, or let it air dry.
The ball must be completely dry before you continue on.
Step 7: Putting It Back Togather
Place the ball back into the hole, then place the ring over the ball so the notch is approximately the same as it was when you turned it upside down in Step 2. Turn the ring back and forth a little until it sinks in flush with the body. Then you just have to turn the ring back clockwise so the rings notch lines up with the notch on the body.
The ball should turn nice and smooth now, and it will track just like it did when it was new.
I hope this helped you breath some life back into one of these things. I like mine much better then new mice even though its 14 years old.