Stihl 042AV reincarnation

[Overlooker]

Before:

After:




I stripped it down far enough that I could pressure test the crankcase and observe the oil seals as I sprayed them with soapy water. All good. I replaced oil, fuel, and impulse hoses, fuel filter, and a plastic guard on the inside of the sprocket cover. I ultrasonically cleaned and rebuit the carb and repaired broken kill-switch wires. I cleaned and repainted the guide bar and spent way too long freeing up rusty links in the chain. The most time, however, was spent removing 25 years of accumulated caked-on oily sawdust throughout the saw.
Bottom line: it runs, idles, and cuts!! However, it's running a 20 inch bar and weighs 3 lb more than my other 20 inch Stihls. But I'm happy as a lark to add another running vintage Stihl to my herd! Thanks for watching! O

 

[Vintage Engine Repairs]

Great saw! Just a word of caution, a pressure test is not the correct method to test oil seals.

Pull a vacuum of about 15inhg / 7psi and rotate the crank shaft a number of times and see if it drops.

Also, ideally you would use a block off plate to seal the intake side, instead of rubber which can hide an aging or warped intake manifold.

 

[stihltech]

The #1 failure is the crankcase gasket.
Blows out the bottom. The pressure test will tell you that . Vacuum test is a must for seals.
I would check the case screws under the clutch. They loosen and then the gasket fails. The cure was torx screws of the same size with the teeth on the back. I know I have at least 2 in storage with exactly the same issue. Was a pretty common repair in the 80s.
Also check the oil supply hose from the tank to the case. Right behind the muffler. Gets a little warm back there. I do not know where to get one at this time. NLA for at least 20 to 30 years.

 

[Overlooker]

Thanks VER and stihltech for the guidance. Fortunately, my 042 is starting, running, idling, and cutting very nicely as it is. I might be able to take what I've learned from the two of you and finally get my vintage 020 running like it should. It runs but not like I'd like it to. O

 

[Vintage Engine Repairs]

No worries, upload a video of it running some time, you can’t beat the sound of old muscle - here is the oldest stihl I’ve owned, late 50’s early 60’s 07. The air vane governor spring has lost its tension so it’s constantly closing the choke and running pig rich , but cool none the less.