Chainsaw problem, Help needed - Houzz- stihl chainsaw leaking gas from vent ,There's an air vent on the gas tank on that Stihl. There's like 6 little holes in a plastic cap. If they get clogged, then no air gets in to replace gas, there's a vaccuum, and it stalls. I had to do a lot of tooloing to get my carb. set up right (260 pro)- follow the book, andWhy Is My String Trimmer Leaking Fuel? | Hunker26/4/2021· Inside the cap is a rubber seal, which can get lost at a refueling stop, causing gas to start leaking. Puncture holes can also come from flying rocks from the cutting head or if you dropped the trimmer against a sharp object. Clean the fuel tank and engine with soap, water and a cleaning rag to help you better determine the source of your leak.