40W Wiper Motors-Possible?

Today I managed to finish a rebuild of my simulator. It previously worked well as a full frame mover but it is now a seat mover with a Kart seat. The motors seem to regularly stall out but I have not done much balancing as I assumed most of my weight would be directly above the pivot. I have seen some motors on these forums with 200W power and 30Nm nominal torque. I did not check the specs on my motors when I bought them but a little bit of research shows that they seem to be 40W motors with a stall torque of 25Nm. Thus, they should be able to handle a max load of about 50Kg with a 5cm shaft. Theoretically, a perfectly balanced system should allow these motors to perform adequately. I think they worked in my previous build because it was quite long and so any error in balancing was minimal relative to the total length. My current build is very short and so even small errors are a large problem and I am wondering if it is possible to balance the rig well enough to get it to work. Has anybody used such low power motors before?

Here is the link to what I think is a spec sheet of my motors
http://www.motors-biz.com/item/800268/Isuzu-Wiper-Motor-with-bracket-NCR-1632-40W-12V-.html

I know that they are not ideal (low rpm is a big one) but I am trying to avoid having to purchase more motors at $100 each as getting them to where I live is expensive.

Thanks for the link but I am already familiar with the idea of moments. Here is a link to my build/showoff thread
https://www.xsimulator.net/community/threads/2dof-kart-seat-mover.9142/

It is like that because the motor on the right cannot move further towards the chair. Should worst case scenario be when the motor lever is at 90-38 degrees? At the level position the angle between the two rods is about 70 degrees. I reasoned that the torque inefficiency would be cancelled by the component of my weight being less. Is this incorrect?
Thx for the advice, I shall move the motor and deal with it being handed through the electronics.