You searched the internet and found that some people are selling a counterweight that can be mounted on a spit. It’s great that you’re doing research before purchasing such an important piece of equipment. A whole pig/lamb rotisserie is a crucial piece of equipment because there can be no mistakes.
Let’s begin. A whole pig or lamb on a rotisserie is not perfectly balanced. The motor needs to overcome the unevenly distributed weight. The critical moment is when the back is turned upwards. That is a crucial situation that the motor needs to handle. Forget about what it says that a “Made in China” 15-watt motor can rotate 90 lbs or a 40-watt motor can rotate 125 lbs. The important information is the torque. Our 110V 40-watt motor with 2.6 RPM has a maximum torque of 20 ft•lb or 27 Nm. That is sufficient for the declared loads, and for our motor, you don’t need a counterweight.
Finally, take a look at this picture. Here, there are at least two mistakes, but our motor did a great job.
The first mistake is that the neck/head and legs are not close to the spit. This creates a significant imbalance, and the meat is not evenly roasted. Bring everything as close to the spit as possible, pull the hind legs all the way back, and tie them to the spit, secure the neck… This may sound funny, but let the pig/lamb on the rotisserie resemble a pouncing cougar on its prey.
The second mistake is that the motor is covered because our motor needs cooling, and covering it prevents that. If you want to prevent the fire from heating up the motor, then place something between the motor and the fire, but don’t cover it. That’s all for now.