Stihl strimmer repair job

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My dad gave me his two year old Stihl FS55 strimmer for repair the other day.  He was using it and it just cut out and wouldn't restart.  The symptoms immediately suggested an ignition rather than fuel related fault.  With the latter you would expect at least some coughing and spluttering before it finally conked out. 

In the workshop, I checked for a spark.  There was none.  The spark plug was all fine and I disconnected the on/off switch to rule that out.  Still no sparks. The time had come to delve further into the bowels of the thing to locate the problem.  Good old Stihl's (like most manufacturers) have held the strimmer together with "star" or "tamper proof" bolts.  Not my favourite fastener but hey they aren't tamper proof at all and they soon came undone.  The strimmer is basically all held together by the plastic casing and the engine just connects onto the shaft with a couple of bolts and engages with the giant speedo cable contraption which takes the drive to the cutter head.

On inspection, the ignition coil was found to be quite rusty which surprised me for a 2 year old tool which has been kept in a garage when not in use.


Stihl FS55 strimmer in bits
Testing the ignition coil A quick test with the multimeter showed that there was continuity between the low tension terminal (which is used to switch off the engine) and earth.  Oh dear, time for a new part. These things are sealed units and not really repairable.  Armed with a piece of cardboard on which I had written all the numbers off the strimmer and the old coil I went to the local parts place and they ordered a new coil which was 29 plus VAT and arrived within a day or so.  That's quite reasonable.  The last coil I bought for a Honda lawnmower was 80.
Here's the new coil installed on the engine. It took a little bit of fiddling about to get the clearance between the soft iron core of the coil and the flywheel right.  After that it was just a question of rebuilding the thing with all the dreaded plastic casings etc and routing the wiring and throttle cable back into the correct places.

Check out the rust on the clutch housing.  Perhaps a little paint might have been a good idea?

Needless to say the thing is now back in action.

Replacement ignition coil installed on the stihl engine.
It's always a bit annoying when something goes wrong after just a couple of years.  However, it could just be bad luck and hopefully the strimmer will be fine now.  In Stihl's defence the part was a reasonable price and quickly available.