Refreshing an old Stihl 038AV

[Mad Professor]

Check your P/C clearance at the skirt w/feeler gauges.

Why are you going to split the cases? Bearings sloppy? Those 038 cranks are pretty durable. Most likely new seals and you'd be fine.

Why don't you want to remove the piston? You can inspect the upper rod bearing/pin, and a new circlip will only cost you $1. Also will make checking P/C clearance easier as well as scraping off old base gasket

 

[Wood Doctor]

I remember six years ago posting a Pic of my 038 AV with its bar locked in a new vise clamp I built for servicing it:

The following day a guy offered me $350 shipped for it. Like a nut I accepted. This saw had more grunt than my MS 361. I still miss it. I replaced the impulse hose, and that's about all it needed.

 

[Pikeshadow]

no issue with the bearings…the crankcase was leaking air - so I wanted to replace the gasket along with the seals to ensure it was tight.
It wont hurt to do the rings too…
That saw is a beauty! I’m looking forward to getting mine up and running again…haven’t used it in 3 seasons.

 

[Pikeshadow]

Got the case split…not sure I needed to replace the gasket, it looked pretty good. But might as well since I was this far in.
I got fuel lines, impulse line and new piston wrist pin c-clips on order, along with a pressure/vac tester….should start getting it back together in a week or so!

 

[Pikeshadow]

Most parts in...New Caber rings on piston, case gasket surfaces cleaned. Ready to marry back up. (I've been distracted by a built-in cabinet/bookcase I've been trying to wrap up.)

 

[Mad Professor]

Trick I learned when I worked at a motorcycle dealership was to use a large flat honing stone and some diesel, to do final cleanup on case mating surfaces. Gets surfaces clean flat and free of any gouges, with just a bit of texture to the surface to hold the gasket well. We did a lot of dirtbikes when motocross was big.

 

[Pikeshadow]

Getting ready to put the case halves back together. I’m scratching my head a little though.
there is a stamped “A” on one side of the piston which I thought is supposed to point towards the exhaust port…but that’s also the same side the ring pins are on, so the ring gaps would straddle the exhaust port if that side is towards the exhaust. (I didn’t get a chance to locate the “A” before taking the piston off, it was pretty well covered in carbon.)
I don’t need to sort that out before the case goes back together necessarily, but didn’t want to start reassembly without a clear path forward.

 

[Mad Professor]

Getting ready to put the case halves back together. I’m scratching my head a little though.
there is a stamped “A” on one side of the piston which I thought is supposed to point towards the exhaust port…but that’s also the same side the ring pins are on, so the ring gaps would straddle the exhaust port if that side is towards the exhaust. (I didn’t get a chance to locate the “A” before taking the piston off, it was pretty well covered in carbon.)
I don’t need to sort that out before the case goes back together necessarily, but didn’t want to start reassembly without a clear path forward.

Ring gaps and pins on intake side. Make sure you center the crank.

 

[Vintage Engine Repairs]

Check your P/C clearance at the skirt w/feeler gauges.

This is so important.

 

[Vintage Engine Repairs]

Ring gaps and pins on intake side. Make sure you center the crank.

This again^^ although there are saws (076 super being an example) that have the pins facing the exhaust port!) double check your manual if in doubt

 

[Pikeshadow]

I got the halves back together and am ready to center the crank and check the P/C clearance. where is the best place to measure the crank to ensure it is centered?

 

[Mad Professor]

I got the halves back together and am ready to center the crank and check the P/C clearance. where is the best place to measure the crank to ensure it is centered?

I check the counterweights to case on each side. It should spin freely

 

[Vintage Engine Repairs]

I got the halves back together and am ready to center the crank and check the P/C clearance. where is the best place to measure the crank to ensure it is centered?

Centring a crankshaft between the cases rarely puts it evenly between the bolt patterns in my experience, I quit bothering on the last saw I did. I have measured multiple bolt patterns, found centre and found it’s actually off what the centre of the crankshaft is when put evenly between the cases. Bearings protrude different amounts on the inside of the cases too from side to side.

Therefore putting the crank bosses evenly between the bearings or evenly between the space of which the conrod rides in the case halves doesn’t always mean the crankshaft is in the centre of the cylinder. Follow the manuals advice which is generally - pull the crank against one side then pull the other on. It’s said for a reason and the crank has a lot of lateral movement, far more than the .5mm space you have either side of the bearing to flywheel boss.

what’s really important is eliminating preload.

 

[Pikeshadow]

After a long break, I finished! (A ruptured Achilles ruins plans for winter projects.)

Replacing the seal and O-rings in the oil pump was a pain.
I didn’t re-run a compression test, but the resistance while cranking it over was night and day. She started right up on the third or fourth pull - cut a few small logs and she pulled hard and went thought them like butter.
The carb is running a bit rich, which makes sense if it was sucking air in through the crank seals and was adjusted to compensate during the last tune up.

I appreciate the help from several folks on this forum. This saw should last me another 30 years…