theoldwizard1
ArboristSite Lurker
So i'm pretty good messing with single cylinder 4 strokes engines and carburetors, but 2 strokes with their diaphragm carburetors makes me pause.
This problem has developed over the past few years and now that it is leaf blown season, it is getting annoying. My Stihl BG85/SH85 will not hold max RPM. At WOT, most of the time it is running below max RPM. If I play with the throttle, I can get it up to max RPM for about 1 second and then it falls back. After 10-20 minutes of use it will rev up to max RPM by itself, but drop back. Kind of like a 4 stroke that has a clogged idle/low speed/primary jet where the governor prevents the engine from stalling. This rev up/fall back is very quick, less than 1 second.
When it falls off of max RPM, it just doesn't sound right.
Typical homeowner use. Fresh E10 (if you are going says switch to ethanol free, save the Internet bandwidth and don't say anything), Stihl synthetic oil (maybe mixed a bit rich, 40-48:1). Starts on the second or third pull every time. It idles well.
As I said, I am nervous about tweaking the carb, because it starts easily and still gets the job done. Start by tweaking the low speed or high speed adjusting screw ?
This problem has developed over the past few years and now that it is leaf blown season, it is getting annoying. My Stihl BG85/SH85 will not hold max RPM. At WOT, most of the time it is running below max RPM. If I play with the throttle, I can get it up to max RPM for about 1 second and then it falls back. After 10-20 minutes of use it will rev up to max RPM by itself, but drop back. Kind of like a 4 stroke that has a clogged idle/low speed/primary jet where the governor prevents the engine from stalling. This rev up/fall back is very quick, less than 1 second.
When it falls off of max RPM, it just doesn't sound right.
Typical homeowner use. Fresh E10 (if you are going says switch to ethanol free, save the Internet bandwidth and don't say anything), Stihl synthetic oil (maybe mixed a bit rich, 40-48:1). Starts on the second or third pull every time. It idles well.
As I said, I am nervous about tweaking the carb, because it starts easily and still gets the job done. Start by tweaking the low speed or high speed adjusting screw ?
