no start leaf blower

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  #1  
Old 10-22-06, 10:02 PM
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Question no start leaf blower

I have a Stihl BG 75 leaf blower that won't start. It has compression and a good spark but even when primed with fuel in the cylinder it won't even pop or fire. I am wondering if the spark could be out of time because of a sheared flywheel key? How do I get at the ignition module on this machine to check? Any other ideas as to what might be the problem?
 
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Old 10-23-06, 02:55 AM
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Although it is possible, it is unlikely that the flywheel key has sheared. I'd be concerned with carbon build-up in the exhaust system (Muffler, spark arrestor screen or exhaust port) or possible piston and/or cylinder scoring. Either way, removal of the muffler would be in order. Whether it be to inspect the exhaust or the ignition components, you would simply need to remove the rewind starter assembly for access to such.
 
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Old 10-23-06, 05:52 AM
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A massive air leak into the crankcase can also cause a problem like you describe, check the seals on both sides of the crankshaft. I have seen this problem on several different brands of trimmers and blowers in the past where one or both seals are loose and not sealing good or when one or the other is torn.
 
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Old 10-23-06, 09:23 AM
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Thanks

I understand what is being said about crankcase leaks being a potential cause of a no start condition but I would have thought that priming the cylinder with a little fuel would have at least got the engine to pop. I will check the muffler etc for an exhaust obstruction which would be a problem. If all else fails I think I will need to ensure that the ignition is in time. On other engines that I have worked on the flywheel is just behind the recoil mechanism. On this machine it appears to be on the other side and access is mysterious. Any hints on how to get there on this particular model?
 
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Old 10-23-06, 09:52 AM
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If the air leak into the crankcase is big enough no amount of priming will cause the unit to pop, keep in mind that 2-cycle engines rely on a sealed crankcase to draw and feed air and fuel into the cylinder. I have had blowers with the crankshaft seals that have come out that would not give any hint of starting until the seals were reinstalled or replaced.

The flywheel is under the blower fan assy., while it is possible it is very unlikely that the key is sheared, unless some thing like a rag or shirt tail was sucked into the air intake, or for some reason the flywheel has come loose.
 
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