020AV

[ssm1699]

Ok, so I have been going through all my saws and servicing them, amongst other things. I have had my Stihl 020AV for several years and finally decided to do a comp test/check the piston through the exhaust port. The only trouble I have had with this saw in the time I have had it, was a melted pulse hose or fuel line, can't remember. Got it as a non-runner and needed a carb rebuild. The comp test gave me 125 psi and the following picture is what the piston looks like through the exhaust port. Would you guys pull it apart or just run it? Not a hard starter and has had plenty of power since I got it, with a 14" hard nose stihl bar and 1/4" pitch chain. The plug looked like it could be a hair richer, so I opened the adjustments a tad. No vac leaks or pressure leaks, that I have found.

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[singinwoodwackr]

I'd take it apart, new rings, clean off the transfer in the cylinder and carefully clean up the piston...unless there is more damage than what can be seen there.

 

[Ax-man]

Doesn't look the best but new rings for sure if they are available . 38 or 40 mm ?? If rings are not available I would leave it alone if the saw runs good .

 

[ssm1699]

Just pulled it down to no covers on it. I am assuming it is a 38 mm based on the casting numbers on the cylinder, Mahle 38zn4. I was kind of thinking tearing it down anyways, for the simple fact that I checked the squish on it and it is at .053". It has a green paper base gasket on it, so could do a base gasket delete on it, along with clean up the cylinder and piston, put new rings in. I think I have a line on rings and possible piston. Just needed to know the diameter first. I knew there was the 2 options for diameter.

The other question on whether the cylinder is even worth the work, found that the spark plug hole has been heli-coiled. I don't have a problem with them. But if I can maybe get a different cylinder that is in better shape, for not a whole lot, might be worth it.

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[singinwoodwackr]

The 0lder 020 that I fixed up is a 38mm and there were no new pistons out there but found a pristine used one for cheap on Ebay. rings were available as well. Cylinders usually clean up nicely...mine did...just took a little time.
I wound up with not quite $100 total into it including buying it for $35. With a muffler mod it is a decent little saw. Refurbishing the old bar took the longest.
I do, however, like the 020 Super I found better

 

[Ax-man]

If cylinder says 38 mm on it then yes you have an older 020 . Parts are going to be hard to find. for a 38mm. The 40 mm super 020 came out later . I have no clue what the squish is on an 020 but .058 sounds like a lot. Personally I wouldn't delete the base gasket for a variety of reasons . Do what you think best but you might not be happy with the saw afterward provided you can get a good seal between the crankcase and the cylinder.

A 40mm top end will fit onto your saw if your looking for more power. Your carb will work but the super had a different carb and there was a slight difference in the case holes to adjust the carb for a super compared to the older av model

 

[ssm1699]

Yes, I definitely have a 38mm p&c. I just pulled it apart so that I could see what everything looked like inside. The cylinder actually looks really good, given what the piston looks like. From the looks of the coat of oil on everything, definitely have a good mix and richness for carb settings. The funny thing is I have found way more 38mm parts, than the 40mm parts. This is the piston and cylinder from my saw. The last picture is the best shot I could get of the exhaust side of the cylinder.

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[singinwoodwackr]

Hm, motor oil used for mix?
The cylinder looks good...will cleanup fine.
That piston might even be salvaged once you get all the crud off of it.
Definitely new rings
If me...
Clean everything, re-ring and run it.

 

[ssm1699]

Kind of what I was thinking for repairs. I have been running stihl orange bottle at 40:1 and 92 octane e-free, through it and all my saws. I won't run any lower octane because of this saw in particular. I was running lower to save cost on fuel, but found one day after some hard use, the fuel was boiling in the fuel tank. Changed to the 92 and that quit. The only other constant probelm I am having is that it is melting the impulse hose. When I got it, the hose was tygon. Replaced it with tygon again and tried to make sure it stayed away from the cylinder, but found a melted hole in it last night on tear down. What is everyone using for impulse lines on these???

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[jltrent]

Like said cleanup, slick off piston and new rings. The piston looks lean scored so I would make sure it gets more lube/gas. IF you have a tach that would be great as you can set it just under spec on RPM s. I have worked on a couple of those, not much fun.......