We have an Ariens snowblower with a Tecumseh engine, and this unit has had an uneven idle since it was brand new. However, it starts on the first pull, even in the winter, and it settles down and works well when it is loaded. The manufacturers of small engines have been trying to reduce emissions since the 1970's, and they are all going to carburetors that run on the lean side, compared to equipment built before. Given that this engine is 17 HP, it likely has two cylinders, and there is a possibility that one of the cylinders runs a bit more lean than the other. This would result in an uneven idle. Cleaning the carburetor should help, but you might never succeed in getting it to idle as smooth as a fuel-injected car.

Thanks ericwi. It is a single cylinder and it was running too lean. The carb cleaning made little difference with the idle mixture as we found it, 1.5 turns out(with a plastic cap restricting movement). We went a 1/2 turn in and it made it worse, too lean. 1/2 turn out made it purr like a kitten. So at 2 turns out it runs great. We had to set the idle down a little bit, but no more popping. Needless to say, we learned more than we needed to about B&S OHV engines, although the head gasket was leaking oil from the push rod galley and needed changing.

" Could the compression release be randomly cracking the exhaust valve at idle "

I see you have solved your problem but just as a point of information, the answer to your question above is NO. In the first place, the compression release works on the INTAKE valve, more but will leave it at that.

Walt Conner