After removing the bolt carrier from the rifle…
From the J.A.Freeman AK47 / AK74 Website
How to change handguards on AK rifles
TOOLS NEEDED: Vise or Quick Clamp,hammer,rubber/wood/rawhide mallet,screwdriver,punch,adjustable wrench,padding for vise jaws(old leather belt,rubber,rags,etc..).
After removing the bolt carrier from the rifle, look on the right side of the rifle below the rear sight. There you will see a lever,move it up and you will notice it turns the gas tube retaining pin.
It has a flat side on it that once it is lined up and down the gas tube can be removed from the rifle by pulling up on the back end of it. Here is the lever in the correct position to remove the upper handguard.
As you can see from the above pic that the gas tube is larger on the rear end and has a flat on each side. Notice the retainers that hold the wood on are open on the bottom. Once the wood is rotated 180 degrees on the gas tube it can be pulled off.
There are 3 ways to get the wood off the gas tube.
Put the rear of the gas tube into a vise with the gas tube upright in the vise,clamping on the flats on each side of the rear of the gas tube. Then with your hand rotate the wood 180 degrees and pull it off.
Clamp the wood side ways in the vise. Then use the adjustable wrench to turn the gas tube 180 degrees and pull it off the wood.
If you don’t have a vise hold the wood in one hand and use the adjustable wrench to turn the gas tube 180 degrees and pull them apart.
Reverse the above process to apply the new upper handguard to the gas tube. I have found in changing the handguards on a couple of dozen AK type rifles that using ways #1 and # 3 will work 95% of the time.
A Quick Clamp can be used in place of a vise to hold the gas tube.
Changing the lower handguard:
Notice in the pic below the small lever on the right front of the lower handguard.
It is connected to a pin on the metal lower handguard retainer. The pin is flat on one side so the lever must be upright or all the way foreword to allow the retainer to slide foreword on the barrel. Use a screwdriver to pry the lever up. Some retainers are pretty tight on the barrel and might require being tapped with punch/hammer to get them to start moving. Once the retainer is pushed foreword on the barrel till it is stopped by the gas block on the barrel. Then the lower handguard can be pulled forward and off the rifle. The lower handguard has a tang of wood that goes into the front of the receiver. Some rifles lower handguards have a metal spacer that attaches to the wood tang. So you don’t want to do any up/down,side to side pulling on the lower handguard. I have found that holding the lower handguard with one hand and hitting the rear sight block with a rubber mallet will remove it easily. Once the handguard is replaced slide the metal retainer on to the wood and rotate the lever into the down position.
Some lower and upper handguards will be loose after changing out the wood. 1/8″wide x 1″long strips can be cut from a coke can or tin can depending on low loose they are and inserted between the retainers and wood.