Stihl BG86 blower muffler mod

[Cujet]

I have 2 Stihl BG86 blowers, (both are non catalyst) one for the FL aircraft hangar and one for my home. While they are about the most powerful hand held gas blowers around, they only make 1HP and are 27cc's. An engine that size should be near 1.5HP. I figured the muffler was probably the culprit. So I pulled the muffler, studied it, and cut a large opening in the middle baffle. I then machined the "tailpipe" nozzle to a larger internal diameter, and machined it for a smooth flow transition.

The result is really interesting. It's sound at idle is quite a bit sharper and louder. But when at full power, it's not noticeably louder than before. Throttle response is considerably better, and yes, it makes more power. I will compare the two blowers side by side when I get a chance, but it's clearly better with the muffler mod.

Interestingly enough, the force from the nozzle is, by feel, obviously faster and higher pressure than before and it shows in the arm-tiring thrust it makes.

 

[BigMoneyGrip]

That was the first thing I did to mine. I also opened up the air box. I retuned the carb and it gins now. I like the raspy sound of the exhaust, too.

 

[tundraotto]

I think I have muffler modded (and tuned carb) on every 2-stroke engine I have. All have improved noticeably - a couple dramatically. They run cooler too.

 

[dlundblad]

I have the BG86 as well. Was very disappointed in it in comparison to my parents BG85. I’ve been thinking about trading it in for the Husky equivalent. I’ll have to look into this.

What did you end up using to machine the muffler?

 

[Cujet]

On the tailpipe nozzle, I removed the screen and drilled it out with a 3/8ths drill bit. Ya can't go much larger without losing the tailpipe. Maybe a few thousandths.

I used a drill bit, to open the baffles inside, then an oval carbide burr to enlarge it.

The muffler has one central baffle. The tailpipe screen locates inside a recess in that baffle. That recess has a tiny hole. That's why when you pull the tailpipe, no additional power results. I drilled that out larger and used the burr to make it about 3/4 inch. But this was still too restrictive. I then drilled a hole in the muffler's internal baffle, directly across from the exhaust port and ground it to as large an opening as I could.

Sorry, I don't have a pic of that baffle mod. But the 2 bolts are in this area, so it's a rectangle about an inch wide and 3/4 of an inch high.

 

[Cujet]

Yes, pulling out the tailpipe now makes it un-neighborly loud and results in even more powa! But even with the tailpipe in, it's now strong enough to blow the medium sized gravel in my driveway, so that's enough. As I really am not trying to relocate gravel, just clear the oak leaves from the driveway. And, yes, it sounds wonderful now.

 

[frankbee3]

Cujet,

I have a feeling that everything in the Florida hangar flies well and runs well. When you're super-tuning leaf blowers, I imagine all the flying machines are tip top.

Do you still have the Cardinal?