FS56 RC puzzle

S

SHB

Active Member
On morning my FS56 RC weed eater started fine, but would bog down when attempting to throttle up, was fine the evening before. So I assumed that the high speed jet was clogged or maybe the spark arrestor. Dismantled the carburetor, inspected, removed the high speed jet, ran carb cleaner through the hole, checked the fuel screen, didn’t really see anything, spark arrestor had carbon, but wasn’t clogged - cleaned it anyway.
Put it back together, seemed to run normally most of the time, but it would occasionally bog down, had to fiddle with the throttle to keep it running. Took it apart again, decided to get a carburetor kit, maybe the diaphragm was dried up or I had damaged it. Turns out a new carburetor cost about RGS same, so went that way.
Left the machine sitting in the shop with a carburetor removed for a couple days until the new one arrived, installed it & put everything together.
Went to crank it, wouldn’t turn over - stuck. Took the rear cover / recoil starter assembly off & tried to turn the end of the crank manually - nothing. Tried a pair of channel locks, barely moved it. Removed the plug, still stiff. Removed the muffler & looked in the cylinder, didn’t see much, put some Kroil on the exposed piston, it got easier to turn. After a couple of minutes it turned over easily. Put it back together, I started and now runs normally. What the heck caused it to lock up? I always use the Stihl oil, one bottle/gallon. And how does one adjust the high speed jet?
 
SHB said:
On morning my FS56 RC weed eater started fine, but would bog down when attempting to throttle up, was fine the evening before. So I assumed that the high speed jet was clogged or maybe the spark arrestor. Dismantled the carburetor, inspected, removed the high speed jet, ran carb cleaner through the hole, checked the fuel screen, didn’t really see anything, spark arrestor had carbon, but wasn’t clogged - cleaned it anyway.
Put it back together, seemed to run normally most of the time, but it would occasionally bog down, had to fiddle with the throttle to keep it running. Took it apart again, decided to get a carburetor kit, maybe the diaphragm was dried up or I had damaged it. Turns out a new carburetor cost about RGS same, so went that way.
Left the machine sitting in the shop with a carburetor removed for a couple days until the new one arrived, installed it & put everything together.
Went to crank it, wouldn’t turn over - stuck. Took the rear cover / recoil starter assembly off & tried to turn the end of the crank manually - nothing. Tried a pair of channel locks, barely moved it. Removed the plug, still stiff. Removed the muffler & looked in the cylinder, didn’t see much, put some Kroil on the exposed piston, it got easier to turn. After a couple of minutes it turned over easily. Put it back together, I started and now runs normally. What the heck caused it to lock up? I always use the Stihl oil, one bottle/gallon. And how does one adjust the high speed jet?
Click to expand...
Take the muffler off and get it red hot with a torch to burn out the slag carbon buildup. I have recovered many 2-stroke engines by doing this.

If exhaust cannot get out, fresh air cannot get in for the carburetor to pull in fuel efficiently.
 
mikehouse said:
StarTech,could the piston have scoring on it? Just wondering?
Click to expand...
To check compression on a 2-stroke I remove the muffler and check condition of the piston, rings, and cylinder. You are looking for scoring and go by experience as to what is excessive or acceptable. A compression test can also be performed.

When I worked on other brands besides Stihl, Husqvarna, Echo, and Redmax, I would see several machines a year that were pooched because of low compression.
 
On especially Stihl they lockup from too carbon.

Best de-carbonizing fluid that I have used is the AC Delco Top Engine Cleaner. I did try another cheaper version and it failed miserably.

With the piston above both intake and exhaust port, fill the cylinder with the cleaner and let sit over night with the spark installed. Next morning clear the cylinder then try starting. When it starts it going to smoke heavily until all the carbon is burned off.

Now this stuff is not cheap or easily found. Stihl does have their own version but most dealers don't carry or even know it exists.

Now if the PNC is scored then its time for a new PNC.
 
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