Stihl leaf blower leaking from exhaust port

gmann1(Lower Michigan)December 12, 2007

I have a Stihl bg55 leaf blower that at one time leaked gas out of the exhaust port. Upon doing some thinking before I wrote in, I wanted to give the most accurate discription of the problem before I wrote in.

Today I went out to my garage and noticed a very black, sooty fluid that had leaked out of the exhaust port of my leaf blower. Upon examining the stain on the floor, I came up with an almost sure theory that it was not accually gas because it would not had been so black. Iliminating the possibility that it has a faulty needle and seat. If this was the problem the leak would have continued until the tank ran dry. 2. The stain was dry, telling me that it only leaked for so long then quit. The only thing I can think of is that there was a buildup of unburned dirty oil somewhere in the motor. When I went to start the motor it ran just fine throughout the intire powerband with a normal idle. Could someone please tell me where this dirty black fluid could be comming from and how to eliminate this from happening again?

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nevada_walrus(Boulder City)

Unscrew the exhaust outlet from the muffler. You will find the spark arrestor screen is mostly clogged up from carbon build up. It wouldn't be long until it would not run worth a spit.

You need to secure this outlet nozzle and screen in a vice or vice grips, use a propane torch to heat up the screen to red hot and brush off with a wire brush. Do this away from any fuel or combustables as the hot carbon sparks brushed off could set something on fire.

This is caused from running at half throttle, dirty air filter or fuel mix that is old or has too much oil in it.

    Bookmark   December 12, 2007 at 5:27PM
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OR, you had one or more instances of the needle and seat hanging open a little. Raw fuel/oil mix ran into the engine and out the exhaust port and through the muffler, picking up some black carbon. Add 1 oz/gal Marvel Mystery Oil or Seafoam to your 2-cycle mix in addition to the regular amount of oil. This will clean up the whole system and keep it clean. I don't think any repair is required at this time. All 2-cycle mufflers are full of black gunk.

    Bookmark   December 12, 2007 at 9:39PM
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Is Marvel Mystery oil that good?!!!! They have been around like....forever!!! I used in my car back in the hot rod days!!! It is an oil also? Does it has any problem using with Stabil, Mobil Racing 2T or Stihl Ultra?

    Bookmark   December 12, 2007 at 9:48PM
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indy452(NC Kansas)

Hmmmm, I have a BG55 and I'm pretty sure it has a diaphram carb and not a needle and seat type.

Sounds like an overly rich condition, and I'll bet that the stain was fuel. Sounds like too much fuel entering then washing out the exhaust onto the floor.
Whats the spark plug look like? Is it clean or wet and oily?
What ratio of fuel/oil do you run? Should be 40:1.
Have you turned any screws on the carb?

You say it ran good last but has it always?


    Bookmark   December 12, 2007 at 11:25PM
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whizzer75(z7 Al)

Diaphram carbs have a needle and seat.

    Bookmark   December 13, 2007 at 9:15AM
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After reading Neil's response,the problem got me thinking. At one point it ran like crap. No power and no high speed. I then tried adjusting the idle screw and both the High speed and Low speed screws with no results. Come to find out, the spark arrestor screen was plugged so I cleaned it and it ran just fine after more adjusting.I feel at this point it is likely the thing is running too rich and collecting unburned gas and oil in the muffler.It will collect a certain amount until it starts spilling out again. My question is this: Can anyone tell me the factory settings for all three adjustments so the thing runs normal again. I do not live above sea level and no it does not have a catalytic converter.

    Bookmark   December 13, 2007 at 10:01AM
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indy452(NC Kansas)

My bad, I was thinking float type.
Anywho, g-mann I tried sending you a PM but the postmaster keeps sending them back. I have the info from my manual on carb settings. I'll try later.


    Bookmark   December 13, 2007 at 3:47PM
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singlebbl(Raleigh, NC)

Are there any "tricks" to removing and reinstalling the muffler? Or is it just unscrewing the two bolts that hold it in place? I notice that there appears to be some kind of flexible rubber gasket material under the heads of the bolts.

    Bookmark   December 17, 2007 at 3:01PM
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