# Craftsman Leaf Blower Run problem



## KenMitchell (May 18, 2011)

I'm working on a Craftsman leaf blower for my neighbor. The problem is that it dies when the choke is opened completely (normal run position). It cranks fine with the choke on but when I switch the choke to full open the engine dies after running a few seconds, unless I almost close the choke back done. It continues to do this even after a good warm up period.

I've check to make sure the muffler is not restricted. It has a Zama carb. I have replaced the diaphragms and checked the needle valve and its adjustment which appears to be ok. I have not removed or adjusted either of the mixture screws (don't have the right tool). The only other symptom it seems to have is that there seems to be more oil than normal coming out of the exhaust.

I have ran out of ideas. Anybody got a suggestion as to what is causing this?

Ken


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## paulr44 (Oct 14, 2008)

There are a number of reasons a 2-stroke will run and die without choke.
1. Bad fuel pump diaphragm (okay, so you put a new one in)
2. Clogged fuel filter.
3. Collapsed fuel line.
4. Restriction in carburetor (rebuilding a carb. doesn't guaranty success).
5. Vacuum leak.
6. Worn piston skirt.
7. Intake gasket on wrong, preventing crankcase impulse from operating fuel pump.
8. Warped intake manifold, preventing crankcase impulse from operating fuel pump.
9. Low compression, resulting in blow-by, preventing crankcase impulse from operating fuel pump and in general failing to sustain combustion.
10. Enough diseases mentioned, onto a likely symptom...

Most likely, there's a restriction in the carburetor by the mixture screws i.e. main jet area. Without the special tool to turn the mixture screws, you probably won't be able to clear the restriction. Usually turning them in 1 turn, then backing them out 2 turns, running the engine and returning them to the orginal position will allow the restriction to clear for larger CC engines. Smaller CC engines often will require the screws be removed, the jets cleaned with an ultrasonice cleaner and/or a carb. cleaning spray, blown out lightly with compressed air, and the screws reinstalled to original position. As a professional I cannot advise you alter the screw setting as this is considered tampering by the EPA and subject to massive fines. Not likely a homeowner would be nailed by the emissions police, but I've heard of them checking units at dealerships in CA.

Be careful with SOME carb. spray cleaners and most 2-stroke carburetors. If they contain xylene, a nasty caustic poison that's great at cleaning gum in carbs., they can curl diaphragms and check valves. Some small CC carbs. don't have check valves, and can be cleaned out without worries.
Paul


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## KenMitchell (May 18, 2011)

Hi Paul,

Thanks for your detailed response. I was able to obtain the special tool required to adjust the mixture screws on the Zama carb. I removed the mixture screws and sprayed Gumout through the holes. I replaced the mixture screws and it cranked fine and after I adjusted them, it seems to be running fine. I'm not sure if there was an obstruction in one or both of the mixture ports or if it was just out of adjustment, but it seems to be ok now.

Only problem is that the pollution level here in south Georgia will really go up since I touched those mixture screws! Please don't tell the EPA.

Ken


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