Stihl FS-55 Valve Adjustment

[Buckeyeman]

Was that with the throttle held open? If so, it's low. That will cause problems with low speed running and starting.

No, I did not have the throttle open. I didn't know you had to.

 

[Buckeyeman]

Cylinder reed valves used to be common on motorcycles. Sometimes they'd have windows in the intake skirt of the piston to increase intake duration (when the reeds allowed).

Now most have the inlet going directly to the cases.

The reeds I have seen in older small power equipment were really inefficient compared to motorcycle reed valves. But the motorcycle V shaped type take up more room. On a motorcycle that's not much of a problem but on a chainsaw or string trimmer, space and weight are the biggest factors. The piston port intake takes less space than a good reed valve. On an engine that has a limited operating rpm range (i.e full throttle all the time) the piston port can make just as much power.

I watched a Youtube video on my exact model, and they said it does not have a reed valve.

 

[Buckeyeman]

When you had muffler removed could you look into the cylinder bore to see if it was scratched? Since you say is old just another thought on things to check.

95 PSI sounds like on low side but like you not sure what it should be.

Does this model have primer bulb? If yes does it fill with gas? Reason for asking is that I have gotten lines swapped and that doesn’t work very well…

Any way you can put your hand or piece of plastic across intake on carb to see what type of vacuum you are getting? Careful you don’t suck the plastic into the carb?

Was the carb from Stihl or chinese clone?

Yes it does have a primer bulb, and yes it fills with gas. Part of the new carb. The carb was a Stihl. I adjusted the carb, and it seems to be running okay. It use to die and not idle. Idles fine now. Now I just have figure out the hard start. I'm leaning towards a coil.

 

[Buckeyeman]

Was that with the throttle held open? If so, it's low. That will cause problems with low speed running and starting.

No I did not. I can do it over and see if that changes things.

 

[Buckeyeman]

FWIW, on the larger FS models -occasionally a weak coil will make them have a bugger of a time on a cold start.

That's what I was thinking also. I'm gonna pick up a coil and see if that helps. It idles fine now that I adjusted the carb. Just hard starting. It is a 2002 model that I bought new. The Stihl dealer couldn't believe how nice it was, and in excellent shape for it's age.

 

[oldnslo]

Is it hard starting both cold and when hot? Can you check spark cold and when engine and coil are hot. Sometimes heat will make electronic ignition coils weaker so might repeat might help point towards a possible cause if spark changes noticeably with temperature.

 

[Buckeyeman]

Is it hard starting both cold and when hot? Can you check spark cold and when engine and coil are hot. Sometimes heat will make electronic ignition coils weaker so might repeat might help point towards a possible cause if spark changes noticeably with temperature.

It seems to be fine when it's hot.

 

[oldnslo]

Since fine when hot and problem cold have you confirmed choke is closing fully.

Have limited experience with Stihl but it seems like every 2 stroke I have ever used had its own procedure to start.

This one prime 3 times and pull and running, next one prime 5 or 6 times to get it to maybe start, next one choke a couple of pulls and then half choke a couple and running.

I believe stated plug not getting wet so would point towards not flooding from excess fuel.

 

[kozal01]

Try not using the primer before starting it cold, my FS55 used to hate when I used the primer

 

[Buckeyeman]

Since fine when hot and problem cold have you confirmed choke is closing fully.

Have limited experience with Stihl but it seems like every 2 stroke I have ever used had its own procedure to start.

This one prime 3 times and pull and running, next one prime 5 or 6 times to get it to maybe start, next one choke a couple of pulls and then half choke a couple and running.

I believe stated plug not getting wet so would point towards not flooding from excess fuel.

I know what your saying. My Stihl blower, and edger I do not have to prime at all and it starts right up. I'm gonna check for a vacuum leak or any loose bolts.