I know this topic has been discussed before, but none of the discussion have the strange problem I sit with.
First a little back round I have a similar saw as your Wen that has been modified beyond its wildest dreams, I made a stand out of 1/8” x 2” angle steel frame, as I can’t weld it was bolted together spring washers were used and two nuts with Red Loctite applied to lock them in place to prevent any movement. 4” from the ground a shelf was fitted again ensuring the legs can’t move out, on the shelf is two 88 pound concrete pavers adding to the security of no movement at all.
Now the coin test was done and the coin fell over between 3/4 and full speed which does not concern at all as I don’t cut at those speeds, so now I add a Foredom Foot Pedal, and the strange things happens, the saw is set to full speed, but when I use the foot pedal I have vibration, take the foot pedal out no vibration, so coming from the electrical industry ( heavy current) not understand electronics I started thinking even though the saw speed control is at full speed and the foot pedal is now controlling the speed is there no some form of conflict between the speed control devices. Removing the foot pedal and setting the saw speed to my preferred cutting speed which is between half and three quarter speed mo vibration at all.
So is thre anybody in the community that can throw some light as to what the problem could be.