Outdoor Power Equipment and Small Engines - Engine backfire and black smoke

I am trying to fix a chipper shredder engine that wouldn't start. I am not sure on the specifics other than it is a Husky engine. The machine is something that would be purchased at Lowes or HD for home use. My initial diagnosis was old gas, so I took apart the carb and cleaned everything out and replaced the old gas. I also changed the oil, cleaned the air filter and checked the spark plug. After putting it back together I gave it a squirt of engine starter and voila we had it running. At lower idle speeds the engine ran fine, but when I pushed it up to full throttle I started getting black smoke and backfire. I adjusted the carberator by turning the the adjustment screw out until the idle decreased and then in until the idle decreased and then moved the screw to the halfway position (which was pretty much where it started). Still no luck. The engine will start and idle fine, but I can't get it to full throttle without the backfire.

Any ideas?

Thanks, Mike

After reading some other threads, I realize that there is probably a high and a low adjustment screw. This might explain why I have it running good at a low idle and not at full throttle. Is there an easy way in general to identify which screw is which?

Thanks again, Mike

Hello Joking777!

I'm assuming the machine is made by Husky, correct? There is no engine made by Husky that I'm aware of. You probably have a Briggs and Stratton or Tecumseh on it. Find out what model# and HP engine you have so we can give detailed instruction.

In general, the high-speed adjustment screw is on the bottom of the bowl nut. Not all engines have one. The symptoms you describe could be caused by a partially closed choke, misadjusted or bad float, restricted air filter, carb problems, etc...