Hard-starting Stihl - But I know the problem

[sritzau]

Hello,

This is the second time I have had the same problem with my Stihl 026 and I am looking for some advice as to what I may be doing wrong.

The symptom is that the saw won't start. After trying a bunch of easy things (new gas, clean the air filter, etc) I removed the plug. I found that the spark gap end of the plug was kind of black and oily looking and that there was a slight buildup of grime between the plug and the engine. By just cleaning up the plug, cleaning away he grime, and re-inserting the plug the saws starts up and runs fine. The first time I had the problem, I thought that the plug might not have been in there tight or that the vibration may have loosened it somewhat, and that the grime had just collected in that gap. The second time it seemed to me that the plug was in there plenty tight, but there was still some buildup of gunk.

Like I said, it's the second time I have had the problem, although the two occurences were a year apart. I have had good luck with the saw, and would like to know if I am causing the problem so that I can stop doing whatever it is I'm doing.

Thanks,

Steve

PS - The saw is completely stock, and I'm running it with the prescribed 50:1 mix, usually with Husky 2-stroke oil since I used to pass a Lowes on the way home. I don't think I swapped the (probably original Bosch) plug between the two occurences. The oily-looking build up on the end of the plug may be from cranking the engine unsuccessfully. I might have cranked it 10 times before admiting I had a problem. I know after 5 times that I have a problem, but for some reason I still pull...

 

[CaseyForrest]

Sounds like you need a lightly hotter plug, or you may be running to rich. Does the saw smoke alot while its running?

 

[sritzau]

It does smoke some but I don' know about a lot. After these incidents it smokes quite a bit. I don't have an adjustable carb. I wonder if my air filter is not passing enough air?

Thanks,

Steve

 

[skwerl]

have you ever opened the muffler outlet? Sounds like flow is restricted, spark screen is probably clogged.

Pull the muffler, remove the screen and make the outlet hole about twice as big as it is now. Then replace the screen and put it back together after cleaning everything up. Clean up the exhaust port while you have the muffler off, be careful not to scratch the piston or drop crud into the motor.

 

[shadyg]

You could try to run a 40:1 mix for a while. ( this would lean it out a little )

 

[stihltech]

problem

Before we start modifying anything, we must have a problem free motor.

I would look at the basics first.

Air: filter clean, choke shutter spring hooked, no other restrictions.

Fuel: fresh, proper octane, carburetor clean and working properly, lines in good shape, vent working.

Exhaust: check the screen, cylinder port and muffler for obstructions.

Spark: Open a plug gap way up, should be blue and bright.

Compression: Give it a rope test.

IF all of these things check out, now lets open the exhaust and readjust the carburetor.

I am not against modding, but you have to have something to work with first.
This is a problem that should not be happening to any saw.

 

[skwerl]

It would be simple to just lean out the high mix screw, except it's a fixed jet carb. I was suggesting something that would normally require more fuel usage in a normal saw. Modded mufflers typically require richening up the carb a little, this one is already (permanently) adjusted for it.

 

[WRW]

If the carb is adjusted while any of the restrictive conditions exist that stihltech mentioned, when that condition is remedied the saw will run lean. Modifying the muffler would have a similar effect, but the muffler cannot easily be readjusted.

Since the owner wonders about the filter being restrictive, I would recommend giving it a good cleaning and burning the carbon off the muffler screen. Every other tank of fuel is a good enough interval for cleaning the filter, in my limited experience.

 

[skwerl]

If the carb is adjusted while any of the restrictive conditions exist that stihltech mentioned, when that condition is remedied the saw will run lean.

WRW, the carb is not adjustable unless you take it apart and swap jets. There is no easy way to adjust the fuel mixture. Since the fuel mixture is fixed and the saw is plugged up, I merely suggested unplugging it and then opening it a little more so the saw can make use the extra fuel being administered by the FIXED JET carb. If you can't tune the carb to the saw, then tune the saw to the carb...

Obviously my advice would be different on a saw with a real carb. In this particular case, the muffler can be adjusted easier than the carb.

 

[sedanman]

If there is more oil then there is less fuel so yes, it does lean it out a little, very little.

 

[WRW]

WRW, the carb is not adjustable unless you take it apart and swap jets. There is no easy way to adjust the fuel mixture. Since the fuel mixture is fixed and the saw is plugged up, I merely suggested unplugging it and then opening it a little more so the saw can make use the extra fuel being administered by the FIXED JET carb. If you can't tune the carb to the saw, then tune the saw to the carb...

Obviously my advice would be different on a saw with a real carb. In this particular case, the muffler can be adjusted easier than the carb.

The non-adjustable carb is why I (actually, stihltech said it first) recommend insuring the filter and screen are clean before modifying the muffler. I would recommend the same if it were an adjustable carb.

I know you aren't a fan of the fixed jet carb, me neither, but hopefully the problem started with just a dirty filter causing incomplete combustion and creating the problem of a dirty screen, negating the need for modifications.