Stihl FS45 weed trimmer

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Old 04-15-16, 05:37 PM
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Stihl FS45 weed trimmer

I had to give up on one due to the cost of diagnosing/fixing was getting to close or more than a new one.

It will become a winter project just to satisfy my curiosity and perhaps learn me a thing or two.

When I got to it I could not get fuel to prime through the bulb. Checked all the fuel lines and filter..all checked ok. New carb, would prime, but same result, not even a burp let alone a bark even with starting fluid in the cylinder or the carb.

Compression is 120 psi. Even went so far as to check the flywheel key. It has good spark even under compression. Tried mixture settings all the way from 3/4 to 2 turns out in steps.

Not even one bark.....

My counter part Mech also went through his motions and had the same luck as I did so....looking for ideas.
 
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Old 04-15-16, 06:49 PM
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Tried another spark plug? Spark arrestor been checked?
 
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Old 04-15-16, 06:55 PM
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Spark arrestor was a thought of mine too. If it has an NGK plug that would be one of the first things swapped to eliminate that possibility.
 
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Old 04-15-16, 07:13 PM
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Forgot to mention the spark arrestor, with it cleaned and removed same result.

Pretty sure we got a Champion plug, tried a couple but no NGK.
 
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Old 04-15-16, 10:10 PM
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Try with the exhaust completely off, the throttle wide open, and a dribble of gas into the cylinder. If it doesn't try to start then, it's either flooded or has a timing issue.
 
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Old 04-16-16, 01:34 PM
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Get a new spark plug, NGK BPMR7A. I have a FS-46 that acted the same way. Have a good one. Geo
 
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Old 04-17-16, 08:32 AM
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It had a bosh in it originally, also tried champion, ngk and oregon plugs, all test good with inline tester but no go with any.
My partner in crime did have it at one point spitting fuel out the exhaust...??? Will try removing the muffler, then dig further into the timing issue which is the only thing the two of us could figure must be the problem.
 
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Old 04-17-16, 06:21 PM
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If the crankcase is soaked it may be flooding the whole time. Try blowing it out with compressed air into the plug hole while you crank the engine slowly. Then try to start it with a few pulls and the throttle wide open. If still no pops or promises, disconnect the fuel lines from the carb and try again with the throttle open several times until it starts or you become convinced it won't . I had one just a few days ago that did this to me, it was a FS74. It didn't really look flooded but it would not start with the fuel lines connected.
 
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Old 04-18-16, 04:35 PM
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I got a Troy Bilt weedeater last week and did not want to pop at all I took the crank cover off and it had water in it. No scoring on piston or cylinder. I had a carb to put on it. After cleaning the crank case and re assembly it ran great.

The bottom shaft was junk so I put a husky shaft and line head on it. Now I can't sell it cause my wife claimed it ~!~!
 
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