Tuning 021

[sir1]

So I picked up this 021 for cheap. No previous history is known. Saw was pretty clean. It ran fine for a while now having fuel issues?

I "went through" the saw
--Fresh fuel (high octane with stihl oil for 5 gal can)
-Clean spark arrestor screen (minimal build up)
-Spark plug (cleaner and has spark)
-Air filter
-Clean saw
-Check fuel filter
-Piston on the exhaust side is not scorn

Saw fires and runs. But feels "weak" Stihl guy said its because its a baby 021, only 35 cc. I tuned the card by ear to the best of my (poor) ability and it ran. I had to have it idle high otherwise it would eventually die.

Stihl guy "fine tuned it" in about 60 seconds said it was abt 1/4 turn off. Problem is when I went to limb with it the problem got worse after about 30 min of cutting. Now instead of just higher idle the saw dies when letting off throttle. I tuned up the idle a bit. Now the saw sounds like it is revving up and down. With occasionally dying. This is worse than before.

Only other thing I can think of is when you first squeeze the throttle it actually sounds like the rmps/power drops almost like "bog" for a second, then it takes off.

Card issues and cylinders issues are my weakness. What next? Compression test, diaphragm/suction test? Carb rebuild?
Tnx

 

[altair]

I'd start with a decent carb clean and diaphragm etc, using proper carb cleaner and letting it soak...maybe it has old fuel which has gummed up and now starting to block the carb some. Or try a cheap replacement carb. If it bog when you give it a rev from idle, turn out the L screw on carb a quarter turn.

 

[HarleyT]

Inspect the fuel line above the tank, you will likely see cracks when you bend it.

 

[sir1]

Inspect the fuel line above the tank, you will likely see cracks when you bend it.

When inspecting the fuel line should pull and inspect all the lines or or just the above tank? I think it has a vent line, an in-tank line and possible another?

 

[sir1]

I'd start with a decent carb clean and diaphragm etc, using proper carb cleaner and letting it soak...maybe it has old fuel which has gummed up and now starting to block the carb some. Or try a cheap replacement carb. If it bog when you give it a rev from idle, turn out the L screw on carb a quarter turn.

In the shop I have Penzoil Gumout Fuel Injector/Carb cleaner. It was given to me. Not sure of age. Never opened. Is this a good product? Stupid question but could you be more specific what exactly is a carb clean? Spray cleaner into carb and run or disassemble everything?

I've rand dozens of tanks of new clean fuel through it already in the last few weeks. Is it possible to still have old fuel somewhere stuck inside?

Thank you

 

[Rockjock]

I suggest you remove the carb, disassemble it and give it a good cleaning with new gaskets. While the carb is out check the fuel line, and also the tank vent. To clean the carb you can use an ultrasonic cleaner or spay it with a good quality carb cleaner and let it sit. Some have had success immersing it in gas for a few days to clean up the varnish. The reassemble it , new fuel line if needed and begin again. That should sort it out for you.