so you're telling me i can drill and tap the threaded section of my muffler and it won't be leaky? i just see it leaking out unless i carefully dremmel the threads off around the hole ... need a tight fit right? anyway the screw on thing just seemed like it would help keep the pressure cause its smooth on top.. i really don't know what to do
No, not the threaded section. When the muffler is fully screwed/attached to the engine, look to where the exhaust and muffler are connected. Tap just to the outside of it. The theory is to inject the smoke oil where the exhaust gas is hottest (i.e. as close to the engine exhaust port as possible). Secure the nipple with JB Weld. This is essentially the same technique I used on my muffler. You will not have any leaks. I'm sure someone will chime in soon and can upload pictures of this. This muffler is for a 2 stroke but the location of the tap is similar on a 4 stroke-right outside the attachment point: