How to change the flint on micro torch roburn mt-770

If this is a Gas jet torch lighter it probably doesn't have one. It uses an 'electronic' ignition which doesn't need a flint. These "piezoelectric' lighters can last for 10 or more years with no problems.
If it is working correctly you should hear a 'click' when you press the button. Gas 'torch' lighters tend to run out of gas more often as the flame burns more fuel at a faster rate to produce the 'Jet' flame. If it isn't lighting properly try refilling it first. These are generally considered a 'cheap' lighter so if refilling doesn't help you could just buy a new one.

"easy-to-use piezo electric ignition"

No flint.

It uses compression of a crystaline material (the click) to generate a spark. Could be dirt has fouled the striker or poor electrical connection between the piezo crystal and the spark gap.

There are 3 common problems:
1. Faulty Ignition. You can try to ignite the flame with a different source of ignition to verify a faulty ignition and eliminate the other issues below.

2. Clogged Nozzle. Compressed air around the nozzle may help free any debris in the nozzle that may cause the problem

3. Incorrect fuel. Some butane may be low quality and difficult to ignite. Try a different source of fuel

There is no flint.
It uses a piezoelectric igniter. Not really replaceable.
Point it at yourself at arms length and see if you can see a spark when you press the button to start it.

to little air - air holes blocked up

I have the same problem

Could be due to the fine gauze in the nozzle becoming clogged due to maybe not using good quality gas refills?.

try to open up the part where the spark would come from. there should be a screw on the bottom or top to open it. This is where the flint would be.

The flint is probably worn down or it broke (you can buy new flints at pretty much any convince store around they are i believe $1-2 for 5 of them.

replace the flint and you will have a spark.

Hi. Get a piece of very fine wire, hardware store is a good source, and run it into the nozzle. Chances are that the nozzle is clogged. Once it is hissing again it will ignite unless you also need a new flint. J.

Google vintage lighters---vendors often have a repair shop