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Chris, Small Engine Technician
Category: Small Engine
Satisfied Customers: 6666
Experience:  20 yrs. experience as ATV, UTV, motorcycle, dirt bike and watercraft technician.
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My Stihl FS310 will not pull over easily. With the plug out

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My Stihl FS310 will not pull over easily. With the plug out it spins easily, as soon as the plug is in it baulks as if there is a hydraulic lock or compression is too high. It will turn over but with difficulty and not fast enough to start.
Valves all seem to be working ok, engine not flooded.
Any ideas please?
Can you tell me some history on the trimmer? Has it been in storage for some time? How long?
Customer: replied 7 years ago.

Strimmer has been in regular commercial use until recently when it was reported as seized up - it was passed to me for checking - it turns over easily with the plug out - no noise or resistance - but baulks with the plug in - there seems plenty of compression with a finger in the plug hole.

Have you tested compression? What were the numbers?


Customer: replied 7 years ago.

I have no figures for compression - I would assume if compression was low it would pull over more easily - not as now when pulling the engine over with the plug in is very difficult.

By putting a finger in the plug hole and pulling the engine over I can feel good compression but that is not my problem - I need to be able to turn the engine over properly as previously

Does it turn over hard with the plug in even if the spark plug wire is off? What did you set the valves to, .10mm intake and exhaust is the correct setting fyi
Customer: replied 7 years ago.

Difficult to turn over with or without plug connector - so probably not timing? I have not adjusted valves as I could not see how they caused the problem - am I wrong?

Sorry for the confusion, you mentioned you DID check the valves. You will need to readjust the valves at this point, that is likely your problem here.






Already Tried:
checked pull cord mechanism - ok. checked valves - seem ok checked exaughst - clear Had carb off but nothing obvious wrong




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