Why does my redmax ebz8500 blower start fine and run fine for a few minutes and then bog down and rev back up? The carburetor, air filter, fuel filter, fuel lines and spark plug are all brand new.

I had the same problem and it was because my "inlet line" and my "primer line" were on the wrong inputs. The input line (long fuel line with the filter) should be on the double barbed input on the carb. The input lower on the carb. Closest to the bulb. Hope this helps. Ran without problems after that.

Is it doing this during idle, or at running speed? Either way it sounds like its starved for fuel. Check your air filter as engines run on an air/fuel mix, and the ratio depends on the correct amount of air entering the carburetor.

Based on the majority of small 2-cycle engines out there, I would suggest rebuilding the carburetor. It's easy to do and kits are usually $10 to $12. Remove the air filter and retrieve the number printed on the carburetor. Then, look on eBay or visit a local small engine repair shop for parts. Remarkably, there are a very small number of carburetors used on a majority of different brands with 2-stroke engines. So, if you buy a kit based on the carburetor number, don't worry if it's not directly referenced to your particular brand of blower.

Sometimes, you can get positive results by partially disassembling a carburetor and cleaning it with spray carburetor cleaner from Walmart or Auto Parts Supply store. But, if you're going to that much trouble, you might as well replace parts as you go. Over time, rubber seals dry out and plastic reed valves leak by. Recently, my chain saw was acting up. I replaced hoses, filters, spark plug, etc. Even flushed the carburetor with cleaner. Nothing helped. But, once the carburetor was rebuilt, it purred like a kitten. I've experienced the same thing with weed-eaters and other engines, too. Fortunately, 2-cycle engines are not complex and usually easy to fix. Good luck!