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compression testing a stihl FS65 trimmer


TreeTrucker's Avatar
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10-27-06, 08:43 PM   #1  
compression testing a stihl FS65 trimmer

Does anyone know the acceptable compression range of a Stihl FS65AVE trimmer ? Thanks

 
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repair_guy's Avatar
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10-28-06, 05:06 AM   #2  
I always look for at lest 90 PSI on no more than the second pull on any 2-cycle engine.90 PSI is the absolute min.

 
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10-29-06, 04:00 AM   #3  
re: compression on Stihl FS65 trimmer

Thanks for the reply. My trimmer runs good, but sometimes it will flood easily when starting it cold or when starting it warmed up. Its kind of puzzling, I thought that the carburator might need to be cleaned. I need to check the spark arrestor screen too. One last question, I'm using a foam type air filter element, should I oil it and squeeze out the excess after cleaning it, of use it "dry" ?

 
Bigwind's Avatar
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10-29-06, 05:46 AM   #4  
Hello all and Cheese: Tree Trucker I think you said your unit runs well but it often >> FLOODS WHILE STARTING<< it. If that's true you probably don't have to clean the carb? You can usually work around this situation very easily. Some two cycle engines will hold prime and you don't even have to pump the bulb at all. So try starting the unit COLD without pumping the bulb. Do that first. If that doesn't work or it's still hard to crank just pump the bulb 1 time and try it, then two, etc. until you find the correct number of bulb pumps that allows for an easy start. Some techs will advise you to go ahead and rebuild the carb no matter what but if it starts O.K. without pumping the bulb why spend the money for a carb kit. You do in fact have a minor problem. There is a microscopic piece of something blocking the vacuum impulse return channel and it is preventing fast bleed down so if you go ahead and rebuild the carb it should fix the the problem and you should be able to crank it normally again. Decisions, Decisions, Decisions? >> COMPRESSION << Repair guy is correct but just FYI I also look for a min. of 65 pounds on the first pull. I have found that if you don't achieve 65 but have 90 on two pulls it will definitely be hard to start and will probably loose enough compression over a short period of time that it will no longer start? They will correct me if I'm wrong but this is what seems to happen to me? >>AIR FILTER:<< I always oil my filters on two cycle engines. Oil it heavy, wrap it in a paper towel or shop rag and squeeze it lightly. The carb on these units can be choked so easily by such small particles it just makes sense to keep your filters properly oiled. I hope this helps! Good luck, Ron!

 
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10-29-06, 06:06 AM   #5  
I omitted the issue of the spark arrester in my previous post. I can't tell you how VERY, VERY, VERY important it is that the muffler be as clean and free of oily buildup as possible. Doing this simple thing will allow 50% of problematic older units to crank without any further repair. Cleaning some mufflers can be quite difficult but you have to clean it or replace it at some point. I'm not allowed to tell you here how to do it easily with 100% effectiveness because it is considered to dangerous. Therefore I Hope your muffler is the type that can be disassembled and you can clean it easily and safely.

 
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