The engine is on a Snapper 826 snowblower from the mid/late 80's. Luckily for me, it saw very little use from the previous (original) owner and has served me well for the past few years. Last year, I noticed some fluctuating/sumbling at high rpms. It liked to have the choke one just a bit in order to run right. Only after the engine was good and warm, could I take the choke off. Today, I pulled the bowl off the carb and gave it a good cleaning. After getting it all together, I could not get the machine to idle correctly. The idle kept going up and down...without me touched the throttle. That little arm on the block kept moving. I played with the screw under the bowl and the one on the side of the body of the carb. I'm now at a point where it idles good and the RPM stays constant when I move the throttle. The problem now is, it won't run smoothly past say 3/4 throttle. Once it gets passed that point, it stumbled really bad. And sounds like it wants to die out. I'm not sure if I'm running too rich or too lean. Any ideas where to start?