We have a Stihl FS45 two stroke trimmer that is about 15 years old and has been used quite extensively during that time. My guess would be that it has roughly 150 to 200 hours on it. Over the last few years, it smokes quite a bit and it has slowly lost power during that time. Smoke is bluish, so I'm assuming that's due to the oil in the mix. It still runs, but sometimes after it has been running for 10 minutes or more at full throttle, it will stall out when brought back to idle. I find I often have to squeeze the throttle a bit to prevent it from stalling out when doing a trimming job, especially after it has run for a while. I have also found that the spark plug gets fouled more often and that replacing it or cleaning it will reduce the stalling behavior for a while. However, it still smokes a lot, regardless. I use the Stihl 2-stroke oil with 87 octane 100% gasoline (no ethanol) at a 50:1 ratio of gas/oil by volume. I admit that I have not used 100% gasoline for the entire life of the trimmer; I started using it over the last 5 years or so- before that I used 87 octane regular automotive gasoline, which would have up to 10% ethanol. So what do you think is the cause of this behavior (the stalling combined with the smoking)? Should I look at the carburetor first or is it likely that the piston and/or cylinder are excessively worn? I did buy a new Stihl FS38 trimmer to replace the old trimmer (being that it is 15 years old, after all), but I would like to get the FS45 in better running condition to have an extra trimmer around. That is, as long as it doesn't cost too much money to do so! Thanks for any help / advice!