My 11224VSR is working but has lost most of its hammering power.

hi
the main driver from the motor spindle is worn

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#1 Check your brushes & brush springs - you will have to remove the switch handle completely to access both brushes
#2 Visual of the armature - is it black / burnt or does it have raised segments?
Most likely it will need an armature if it has run for any length of time with bad brushes.
The armature comes out the front of the motor housing so you need to remove the gearcase to access it. Armature 2610003331 for Bosch Power Tool eReplacement Parts Carbon Brush Set

special grease is used not oil order number 1 615 430 001 is the right grease for it

If you mean the front striker pin you will need to remove the circlip up inside the spindle. You can see it through the two little holes just above the spring.

Its usually a problem with the selector knob... depress the button fully and turn it passed the selection markings and pull it out to remove it

If both functions, hammering & drilling, work correctly on their own but not together your selector knob may be the issue. On the back of the knob is a driver pin that moves the necessary parts to make your tool drill, hammer, or both. If it isn't moving those parts to the exact right place, one or more of the functions may not work. Try moving the selector halfway between positions and see if the gun hammer-drills. If it does you have problems with the selector or drive pin. If it still does not you may have internal parts problems that can only be diagnosed by working on the tool with the knowledge of how it works and how everything inside should be.

You could have lost one teeth on the gear wheel . Once it is rotating the system will not miss the lost teeth, until you loose some more teeth then you will loose power and the drilling will become jerky and might even stop on applying pressure

Must use an SDS style bit.
INSERTING:
Clean the insert shank end of the accessory to remove any debris, then lightly grease with a light oil or lubricant Insert accessory into the tool holder through the dust shield, while twisting and pushing inward until it locks automatically into place. Pull outward on the accessory to be certain it is locked into the tool holder.

REMOVING:
To remove an accessory, pull and hold locking sleeve backward and pull bit forward. All accessories should be wiped clean after removing.

Please rate this answer of it's helpfulness. Good Luck and have a great day. Jeff

If it is an 1199, forget it. Replace the brushes and do NOT use for hammering. It is a design problem. My unit was repaired 4 times and hammered about 5 holes each time before same failure.