I noticed on your Manchester Vac's website that you sell the Carbon Brushes for the YDK Motor.
I would love to know how, after soldering them into the old holders and refitting to the motor, you get these to work without sparks flying everywhere.
I'm not using duff motors either. I'm using motors that work ok with the old Carbon Brushes in but on checking them they are very short and will need replacing soon. The armature is also okay on these motors but despite trying I cannot get these new Carbon Brushes to work without sparks flying everywhere.
It is even more baffling as I have in the past replaced Carbon Brushes in Washing Machine Motors etc but never had a problem with Sparking afterwards.
I have also bought the Dyson Repair Book but it doesnt mention about changing the Carbon Brushes in there.