Stihl FS45 Trimmer Issues

[raffy]

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!

 

[jeepman3071]

Are there any adjustment needles on this carb or is it non-adjustable? I'd start with a good cleaning and adjustment first. Even though it is older I wouldn't assume it is worn out. I have a Makita 2-stroke weed trimmer that is from 1996 and still runs awesome even after lots of use. More smoke could just mean it is getting too much fuel.

 

[WyrTwister]

That would be my guess , too . Clean the carb real well ( do not know if carb kits are available ? ) . Then try to adjust the carb . I have a Sthil string trimmer , too , that I seldom use because I have to mess with it to get it to start & run . I do not know , it might run better if I would use it more ?

 

[JohnnyJohnson]

The problem with that when string trimmers get that old the parts are really getting hard to find. I know because I have a 25 year old Shindaiwa. You might try a little higher octane. I use 93 octane premium in mine. But after even 25 years my Shindaiwa barely smokes and is a two cycle. Big issue is do you drain it every year when you're done for the season.

 

[jeepman3071]

Originally Posted by WyrTwister

That would be my guess , too . Clean the carb real well ( do not know if carb kits are available ? ) . Then try to adjust the carb . I have a Sthil string trimmer , too , that I seldom use because I have to mess with it to get it to start & run . I do not know , it might run better if I would use it more ?

Using it more helps to burn the old fuel out, but the best case is to dump out the fuel and run it dry before storage.

 

[raffy]

Thanks for the responses! I'll also admit that I typically do not drain the fuel from my trimmer and blower at the end of the season, although I always drain the gas/oil mix out of my Stihl chainsaw after using it because I use it so infrequently. I think I will start draining out the fuel from the other 2-strokers like that from now on! I do ALWAYS put in PRI-G fuel stabilizer into all the gasoline our small engines use (4-stroke and 2-stroke). I will check and clean the carburetor and yes, they do have carb kits available for the FS45 engine (in fact, I can get a whole new carburetor with all gaskets on Amazon.com for roughly $15 to $20 shipped!). The carb is adjustable and has needles for idle and mixture. I hate messing with those but there probably are good videos on YouTube or elsewhere on the Internet that describe how to do it.

 

[Astro14]

Smoking, stalling, fouled plug. Sounds like it's running rich. I've got the same trimmer. I've found that: 1. stabilizer doesn't help much. Tru-fuel works well for long storage. 2. Ethanol in regular gasoline causes degradation of fuel lines and parts. I would try cleaning the carb and adjusting it to run a bit more lean. For $20, if it's a Stihl part (not some knockoff junk) a new carb is worth a try.

 

[rekit]

Could the rings be worn out? Compression down? That is a lot of hours. I run a 2 stroke chinese RC airplane engine. 20cc. The original ring was crap and not uncommon, so there is a guy that makes proper rings for these. World of difference. Before it turned over so easy you would check that the spark plug was even in LOL.

 

[Patrick0525]

Originally Posted by rekit

Could the rings be worn out? Compression down? That is a lot of hours. I run a 2 stroke chinese RC airplane engine. 20cc. The original ring was crap and not uncommon, so there is a guy that makes proper rings for these. World of difference. Before it turned over so easy you would check that the spark plug was even in LOL.

Please posts link of the guy who does custom rings for air cooled engines?

 

[Linctex]

Originally Posted by rekit

Could the rings be worn out? Compression down? .......original ring was crap and not uncommon, .... World of difference.

THIS. Everything you described points to a bad rings or rings. Not fuel mixture.

 

[Audios]

Ive had pretty good results with a good shot of techron mixed in with each tank or so. First starts in the spring have never been an issue with my 7 year old echo. I do run premium fuel, although in NJ theres a good chance its anything up to E15, and mixed in Stabil in the 5 gallon can.

 

[das_peikko]

Originally Posted by raffy

The carb is adjustable and has needles for idle and mixture. I hate messing with those but there probably are good videos on YouTube or elsewhere on the Internet that describe how to do it.

It's called setting the fuel / air mixture ratio. The ideal mixture ratio for most engines is 14 parts air to 1 part fuel. Modern fuel injected engines use a variety of sensors informing the computer on which way to adjust the mixture. Carburetors rely on humans for this adjustment. It's the biggest variable there is because air density changes daily.

 

[Mr_Joe]

Did you mention the spark arrestor? Cleaned or removed?

 

[raffy]

Thanks for the comments, everyone! I do have an extra carburetor for this trimmer (brand new), so I will probably install it and see if that helps first - and of course I'll have to adjust it but YouTube has some good videos on how to do that. My Stihl doesn't seem to have a spark arrestor, just the muffler (which only reduces the noise a little, LOL!). I think only the California trimmers had spark arrestors back when I bought it; maybe they all do now. I now only use 100% gas as I mentioned earlier, but didn't for the entire life of this unit. I strongly recommend using only 100% gasoline for any outdoor power equipment. It's just not worth having ethanol precipitate out, absorb water, damage seals, and otherwise cause problems. More people in my locale seem to be wising up to that notion, as more local gas stations now offer 100% gasoline than ever have before around here.