Łucznik Sewing Machine Engine and U-118/1 Speed Regulator: Overheating and Humming Issues

The motor with the regulator is on the Łucznik sewing machine, but it doesn't matter. U-118/1 pedal (foot switch).

The problem is that the machine is over 20 years old and when you press the pedal, gently or to the max, it often happens that the engine starts to hum and starts only after turning the rotor by hand.
The problem is the same after removing the strap in the machine, i.e. removing the mechanical load. Even on the removed belt, the engine is very heats up and makes a different noise than usual.
What I did:
- initially lubrication and cleaning of the entire machine (after no effects, removal of the transmission belt - mechanical decoupling)
1.Engine:
- checking the brushes, springs, brush holders (large stock of brushes)
- commutator cleaning
- tightening of connections
1.Regulator / pedal
- checking the foot switch (visual carbon resistors OK, capacitor without leaks)
- pedal resistance starts from 640? and goes smoothly to zero (on the pedal on the plate, minimum 800? ;)

My questions:
Does the capacitor in the pedal have a starting or anti-interference function? Could it happen that a capacitor has dried out for more than 20 years?
What could be the reason the engine starts 5 smoothly ok then starts humming and OK again? Why is the engine very hot after 1.5 - 2 minutes despite the lack of mechanical resistance? Can the motor have a shortcut on the winding?

andrzejac83 wrote:

Why is the engine very hot after 1.5 - 2 minutes despite the lack of mechanical resistance?

Do you have a problem to measure the current consumption with an AC ammeter at idle speed and compare it with the rating plate? If I am not mistaken, there is 90W / 05A there

I suspect a damaged rotor in the engine.

What is the function of a capacitor in the pedal? Starting or filtering for the engine?
Could it be the cause of engine starting / humming problems and engine warming up?

After taking it out, it turns out that the capacitor has poured out, and the photo is attached. Instead of 0.1 uF, it is measured at 0.075 uF. Could this be the reason?

Thank you for your attention regarding checking the motor current. I understand that more than 0.5A will mean damage inside the motor (lower resistance of the rotor / stator winding)? Can I measure the current in front of the pedal or behind? In my opinion, it does not matter, provided that the pedal is pressed all the way and the carbon resistors are bypassed by the metal plate in the pedal housing? I'm not wrong?

What does the engine or the regulator heat up quickly? If there is a problem with starting and you need to spin the wheel from the motor, it is the motor's fault, even if it makes a strange noise, check the condition of the bearings and commutator.

Added after 45 [seconds]:

It's best to disassemble the engine and show photos, although not everything is visible with the naked eye.

This capacitor is anti-interference and replace it with the same. If the engine heats up and lacks power, it is defective.

Norwidus wrote:

What does the engine or the regulator heat up quickly? If there is a problem with starting and you need to spin the wheel from the motor, it is the motor's fault, even if it makes a strange noise, check the condition of the bearings and commutator.
Added after 45 [seconds]:
It's best to disassemble the engine and show photos, although not everything is visible with the naked eye.

The engine heats up.
The rotor turns slightly, no resistance. Commutator is not burned out, brushes OK.
The engine, despite the passage of years inside, seems to be in great condition.
As in the week, I will buy a capacitor and it will not help back with photos.
I'll do a motor current measurement and maybe how will the stator windings succeed