I had to plug one of my Bisson tubes for reliable OS 1.60 running. I'm running a 24oz tank, without a pump, and was not getting enough backpressure to richen things up suitably. Plugging one of the tubes did the trick. The stock muffler only has 1 output tube, and the 2 tubes on the Bisson was not providing enough restriction. You may notice that on the Bisson, the tips of the tubes are beveled over to create more restriction. In my particular case, this was not enough. If you need to run your needle out more then 2 turns to richen it up, then I would suggest plugging one of the Bisson tubes. Try it first and see ?

My OS 1.60 now performs beautifully.

> Jim