This Yamaha Blaster atv has been sitting for awhile and won’t start. There is a good chance that the carburetor is probably dirty. The two stroke gas, as with any gas, gets bad after time and starts to cause buildup in the carburetor. The carb will be removed and cleaned out, so that it will start well again. Even if this or any two stroke engine will run after sitting awhile, there is a chance of build up of bad gas that could cause it to lean out and possibly even ruin the engine. So if your not sure how clean the carb is, it’s cheap insurance to clean it. The carb is located behind the engine.
The two stroke exhaust pipe is a very important tuning tool of a two stroke engine. A stock two cycle engine is usually tuned to make reasonable power across the power band. Aftermarket pipes are called expansion chambers because of the way the pipe expands in the center. A 2 stroke engine has a very strong exhaust pulse that occurs as the piston passes the flat top of the exhaust port. The quick pressure pulse moves quickly down the pipe and creates a shock wave as it exits the end of the pipe. Part of this strong pulse wave travels back up the pipe and if timed correctly bounces off the piston as it travels downward.