I AM ENCOUNTERING PROBLEM ABOUT DC

Jal
You need to provide some more information. What type of motor it is - shunt, series or compound? The figure 1.25V across armature does not make sense. You are saying that the motor does not rotate so the given voltages are at standstill. Is it a compound motor with a high resistance connected in series with the armature? Please check field and armature currents as well and post data.

KJB

Suggestions:
1. Check or clean commutator. There are some good postings in this Forum with references.
2. Measure voltages at the motor terminals. They are supposed to correspond to the motor rated voltages.
3. Check motor winding coils resistance/impedance for continuity.
4. Check brushes, braces, etc. for their correct positions and quality.
5. Make sure that the shaft load is as designed, and that there is not any overload.
This may be just a start with more to follow.