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ranwell1, Small Engine Technician
Category: Small Engine
Satisfied Customers: 10304
Experience:  Owner of Large Small engine repair business. Over 39 years. Certified both 2-cycle and 4-cycle engines
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I have a stihl fs360 strimmer, it starts and from cold can

Customer Question

I have a stihl fs360 strimmer, it starts and from cold can be throttled up to max. As it gets warm the engine starts to bog down on wider throttle openings, if you held the throttle lever all the way in the engine stalls.
Any ideas.
Ps when it is bogging and you leave it to return to tick over you can get a clean rev out of it once then it bogs again
Thanks clive
Submitted: 2 years ago.
Category: Small Engine
Expert:  ranwell1 replied 2 years ago.
This sounds like the exhaust ports are clogged or the spark arrest0r screen is clogged in the muffler.When this happens, it restricts the exhause gasses from comming out properly .Check the spark arrestor screen to see if it is clogged and if it is clean the carbor frm the scree with a wire brush or replace the screen. It is clean then check the exhaust port. You will have to take the muffler off and look inside the engine exhaust ports and see if it is clean. A clogged screen or ports will cause the bogging down and lack of power.While you are there, look at the piston and see if there is any scoring on the piston. If the piston is scored then you will need a new engine. The scored piston will cause the engine to bogg down and lose power because it is bypassing compression.If none of the above things is wrong, then I suggest that you have the carburetor cleaned and rebuilt as you may just have a dirty carburetor or bad diaphrams.Let me know what you find.Please give me a good rating as this is the only way that this site pays me for my time.
Customer: replied 2 years ago.
Thanks for that, the exhaust is clear, exhaust port clean, piston looks fine.
Could it be the coil breaking down, I.e.once it gets hot. Noticed as I worked on it today that the length of time from running normally to starting to bog down on higher throttle opening reduced significantly
Expert:  ranwell1 replied 2 years ago.

It is possible that the coil is breaking down, but usually when a coil breaks down, it stops producing spark altogether and the engine just shuts off all at once. If the piston and exhaust is ok, then your most likely issue could be the carburetor that is not getting enough gas. It may need to be cleaned and rebuilt. But at this point, we are just guessing what could be wrong, but my best guess is the carburetor not getting enough gas in high throttle or the carburetor is getting too warm and having a VAPOR LOCK. Try using Premium gas and you may find out that that is a big help. All 2 cycle engine should use only 92 octane or higher fuel. let me know what you find out. Please don't forget to give me a good rating for my effort. This is the only way that this site pays me for my time. Feel free to continue contacting me if you need more information.