Tattoo Machine Troubleshooting 
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Needle Bar Rubs Tube Troubleshooting Answer # A140
Problem	Machine bogs down.
Because	The needle bar is rubbing inside the tube.
Check	a) Position of the needle bar on the nipple of the armature bar and b) Position of the armature bar.
Why	Needle bar rubbing causes reistance.
Cause	Needle bar too far forward.
Remedy	Push onto armature bar or move armature bar back.

Also see  needle insertion in tube.