Joe, I never found a difference with it in, or with it out. I assume it has something to do with creating a venturi effect, or modifying it. I didn't even know I'd forgot it, until I saw it laying on my bench. Ran it like that anyway. No difference. Did some work on the engine later, removed the carb and installed that piece, again, no difference. (I am not a Briggs expert)
I removed one on a 3hp. It was basically a stock engine other than exhaust, timing advance and jet increase. I was disappointed in the throttle response. I worked with it for awhile and wound up changing the carb out for another stocker. I know on engine with a little more work done it's supposed to benefit. Hopefully I'll be finding that out on my Taco 5hp shortly...
Sent from my iPhone using Tapatalk
Sent from my iPhone using Tapatalk
Here's a link where we were talking about this awhile ago. Note that not all pulsa jet carburetors came with the mixing spiral. I am fairly certain one was not present on my Raptor, which is far from stock.
I have found a trick to remove the spiral on Briggs carbs. I have found placing the carb in the freezer and letting it get frosty cold will cause the spiral to contract, and it will pull/fall right out on its own. To replace the spiral, freeze just the spiral and it will slide into the carb, once it warms up it should (in theory) stay in place.