The best way to modify a Ryobi chain saw is by adding more exhaust channels to the muffler. This will allow greater airflow, which will keep the machine cooler. Cooling down the parts means your chain saw will last longer and its fuel efficiency and power will increase. This can be achieved with a few hand tools.
Purchase a muffler modification kit. You can find these being sold on chain saw websites such as Arborist Site. Some hardware stores also stock them as do chain saw outlets.
Remove the old muffler using your drill and screws. The screws can be located underneath the muffler and are fairly easy to get out. Note that some muffler modifier kits do not require you to remove the muffler, but instead to drill the modifier into place on top. Check your kit instructions first.
Clean the parts inside the chain saw with diluted ammonia. Use one part ammonia for every 10 parts water, or a cup of ammonia for a gallon of water. Rub lightly with a soft bristle brush dipped in the solution. This will often increase performance and prevent damage to the engine later. Wear protective gloves when handling ammonia.
Install the muffler modifier. Most modification kits will require you to take off the old muffler and attach the new one. Some only provide a replacement exhaust valve or provide an attachment that you drill into the muffler.
Test your Ryobi chain saw to ensure the muffler has increased airflow to the engine. It should be significantly louder than before. Also test if its cutting strength is improved and if the chain saw body stays cooler than before.
Installing a modifier may void the warranty. Check with your supplier first. If unsure, take the chain saw to a professional, who can modify it for you. If you do not attach the new system properly you can destroy the machine. Always use ear protectors when working with a chain saw. The noise of the chain saw will increase significantly after the modification.