How do I change the blade on my Makita MLT100 table saw?

I can't find this saw at Makita; so, generally. Follow all safety precautions. :-)
If the saw is running rough, the first thing I'd check is the brushes for the motor, especially if it has any age. These are fairly inexpensive and will solve a lot of woes. The next thing would be to check the thumb switch, if it has one. This is the switch that allows you to pull the trigger to run the saw, if it's just a button, then check the actual trigger switch to make sure it's working properly as it probably, not always, also engages the brushes to reverse the motor for a second, to slow it down so it stops faster.

So, check the brushes on the motor, if they show any signs of wear, it's probably them. 2nd, check the switch. Please let me know and if I've helped, give me a vote up. Thanks.

I don't have table saw but my guess would be power shortage. Maybe try plugging it in different amp circuit and see if that makes difference.

Did you manage to get in contact with the manufacturer of your saw? They would surely help you with your problem.

Sounds like the motor is wore out! Or maybe the belt if its belt driven

You almost answered your own question.. As you've already discovered, the blade will slowly move as you're feeding stock to cut, so you can either locate the missing locking nut/screw, or buy a replacement from the nearest Toolshop.. Or dig out a 50-75mm machine bolt from your junk box & use this as a temporary replacement.. You'll have to check for the correct thread size 1st as they may differ from country, but I'm sure that'll solve the problem for now..

It likely has too large a blade. It may be a 9.5 inch saw with a 10 inch blade on it. This can go unnoticed until you want to use the router mount or somesuch. Otherwise, it could be debris on the screw base.
anyway, that's where I would start.
Farmerbear at Fixya

i would say the table is twisted then, strip it down first and if you need to "bend!" it back so it works

This link will take you to Makita and display an owners manual where you will see that the saw should have came with the necessary wrenches to change the blade. If they are not available I have used two different methods. Take care with either, that blade is just waiting to getcha. 1. I have clamped a pair of vice grips directly on the blade and let them stop against the saw top to keep the blade from turning or 2. I have levered a peice of soft wood against the blade to keep it from turning. According to Makita the thread is righthand, so you can apply the righty tighty lefty loosey rule to determine which way to loosen the nut. Good luck I hope this helps.

Did you remove the center plate? It has to come out before you can remove the blade. Also make sure that the saw is unplugged before you go any further. If you still have questions contact me and I will do what I can. Also if you would like you can download a schematic of this tool at Makitatools.com just type in your model and look at the schematic. Good luck