Stihl trimmer will not start...

[russ71satellite]

I have a Stihl FS55RC trimmer that will not start. New plug, new fuel/oil, I dissassembled carb and cleaned it. I am getting a good, blue spark at the plug. I am getting fuel to the cylinder.

All I can get it to do is spit out of the carb throat. I think it is timing, but I don't see how the timing could have gotten off.

also, if it is a timing problem, how would I go about setting/checking the timing on this thing?

Thanks for any ideas...

 

[Kneejerk Bombas]

I don't know about that specific tool, but two stroke timing is controled by the flywheel position on the crankshaft. It's held in place by a little key that sits in a groove in both the crank and the flywheel.
They do shear, rarely, but they do. I had a blower key shear this summer when my tee shirt got sucked into the blower fan/flywheel.
To check, you need to pull the flywheel.

 

[04ultra]

Pull muffler look at piston and also make sure you clean muffler screen.......




.

 

[Kneejerk Bombas]

Pull muffler look at piston and also make sure you clean muffler screen.......




.

Good call. Those newer mufflers have small openings and fine screens. Then they make them so they don't come apart unless you undo the seam all the way around the muffler. Inside the can they sometimes have baffle plates that have little holes that clog easily, especially if the tool is being run too rich or too slow.

 

[russ71satellite]

thanks for the info, guys. I'll start out by checking the muffler screen and go from there. I'll update.

 

[yo2001]

Not too sure on the trimmer but on my old BR400 had a spark arrester on the end of the muffler clamped on. It would cause the saw to not crank like it should until it took it off.

 

[russ71satellite]

Update....

pulled the plastic shrouds off everything, and when I turn the flywheel, the two "contact points" (for my lack of a better term) line up with the coil when the cylinder is at TDC. I get no feel of a broken key, etc when I rotate the flywheel. It lines up this way every time.

Therefore, that may mean the muffler situation suggested earlier. I have hit a roadblock, though, because I can't get a star tool down inside the muffler enough to remove the muffler. The shoulder of the socket holding the star bit hits the flange on the hole before it can get down into the muffler enough.

Will try to find the right tool so I can remove the muffler.
Thanks for the help, and I'll update more.

 

[banjobart]

You have it, go buy a screwdriver handle T-27 or other size "torx" driver to fit at the hardware. Pick up an entire set while you are there.

 

[Rookie1]

You took spark arrestor screen off to get into there right. Try to start it now. You can see the piston right.If you can see it then there will be no obstructions.

 

[russ71satellite]

Rookie...I guess I may be confused. Earlier in this repair, I did remove a white colored piece of "filter" material from the muffler.

Tried to start after that, and no help. From earlier posts on here, I was under the impression I had to remove the muffler and take it apart.

As far as the piston goes, the only way I can see it is by looking down the spark plug hole.

Should I go ahead and remove/dissassemble the muffler?

Thanks

 

[russ71satellite]

another update...took muffler off. I found one small screen, about one inch square, which was perfectly clean. I have not taken the muffler apart yet. I tried to start it up without muffler on, and it is trying to run, sputtering, etc as long as I am pulling on the rope. At the end of the pull, no running.

So...it seems to be doing more now, without the muffler on, but still no run.

Ideas at this point?
Thanks

 

[treemandan]

You should be able to see the piston with the muffler off, the exhaust port is a hole in the side of the head. Also with the card ass. off you can see it.
If you have fuel, spark and air then you have no compression. Look for stratches on the piston through the exhaust port, muffler off.

 

[russ71satellite]

Yes, I can see the side of the piston, and it seems fine when viewing with the naked eye. Cylinder walls seem shiny also, at least the part I can see.

When I pull the rope, or turn the motor by hand, I feel what seems like normal compression, for what that's worth...

 

[(WLL)]

dump some fuel down the muffler and see if she will fire, if so you are not getting fuel. im thinking you made a mistake while working on the carb

 

[russ71satellite]

I'm getting fuel, because it is getting on the spark plug and I can see it in the cylinder and around the piston...

 

[(WLL)]

i wood think you have an air leak, check the rubber boot behind the carb. inspect the fuel lines fer cracks. if all is good you need to check the crank seals.

 

[OLD CHIPMONK]

It sounds like a flooding problem.First Walbro or Zama carb. ????????? Remove the carb. & fuel pump diaphram. Look at the tang & needle assy. probably bent during cleaning. Next ck. the needle & see if it's tip is pliable or hard. You may need a Walbro carb. rebulid kit for around $14.95. Fuel should not leak past the needle when properly set-up.If the pump diaphram has a space on the inside metal stud make sure the needle tang is hooked to the metal space on the diaphram . If it's a Zama Carb. your gaskets are in the wrong sequence. Good luck !!!!!!!!

 

[OLD CHIPMONK]

I'm getting fuel, because it is getting on the spark plug and I can see it in the cylinder and around the piston...

Definetely a flooding condition. Work on that carb. & it will run again!!!!!!!!!