Bought a Stihl 024 Frankensaw on eBay for $61

[John Lyngdal]

Just thought I needed a project saw with a future of being a loaner saw, so I bought what was listed as an 024 on eBay for $61 plus shipping. If it was a total piece of junk, I could part it out and recoup the purchase price.
The description was:
"1- Used STIHL 024 Power head / No bar or chain
Unit for parts or repair. Low compression , believed to be scored cylinder.
Fairly clean machine, appears to be in decent shape overall."

Indeed the unit looked like an 024, with the lower cylinder cover profile as compared to an 026. Then again the cylinder cover badge was missing. First thing I pulled the spark plug and measured the compression, about 160 psi. Lower than factory new, but still respectable. Next step, off came the muffler to look at the "scored cylinder". A few marks on the piston, but the cylinder wall was perfect. Oddly I could see the top of the piston drop clearly drop below the exhaust port. Out came the digital calipers to measure the bore diameter, it was 44mm and not the 42mm spec for the 024 saws. So at least the saw had a 026 cylinder on it, and I could see the Stihl and 1121 markings on the base of the cylinder so it's clearly an OEM cylinder. Back of my mind I'm wondering if this was a 026 cylinder installed on a saw with an 024 crankshaft, so next I measured the squish. It was a fat .056" or about 1.4mm, while the stroke difference between the 024 and 026 is 2mm. Next I looked for a cylinder base gasket, and it was clearly present, so clearly the saw had a 024 Super or 026 crankshaft. Time to take a look at the top of the cylinder more closely and compare it to an 026. Bingo. Bubba had worked on the saw and to make the cylinder cover fit after the 026 jug was installed he removed a portion of the cooling fins on the top of the cylinder.

Based on the air filter, I'm guessing that this saw was was a 024 Super that had a 026 cylinder installed on it. Just wouldn't have made any sense to the put 024 parts on a 026. Tach tuned the saw and it pulls a 18" bar with a .325" chain at over 14,500 rpm before I added another 1/4 turn on the high needle and dropped it down to about 13,500. The saw still has issues as it idles rough and starts hard. Going to run it for awhile and see if that improves and if not I'll rebuild the carburetor. Time to order a new air filter and plastic parts to make it right.

 

[drf255]

I like it.

Interested to know if it's a super crank or not. Sure sounds like one. Or the guy swapped all the plastics onto an 026 case and jug.

Look at the flywheel and see if the fins look archaic or smooth like your 026. The 024 flywheels have choppy little fins that will make you wonder what they were thinking.

Remember, the stroke different is 2mm, but that's 1 up and 1 down, so there's only gonna be .040 difference, not .080.

I'm interested in swapping a 26 head to a non super 24 and seeing what happens with some porting and machine work.

Here's the flywheels. 26 on left, 24 on right.

 

[John Lyngdal]

Thanks for the tip about the flywheel. Just checked and it's the version on the left you identified as one from an 026.I'm wondering if they used the 026 style flywheel on 024 Super saws or if the previous saw owner replaced this part as well. The more 026 parts I find, leads me to believe that this was an 026 all along.

Thanks for pointing out that the 2mm stroke difference is 1mm up and 1mm down. So a .056" squish keeps the possibility of the plain 024 crank shaft as a possibility. When I pull the jug I need to see if the gasket is a 0.5mm or a 1.0mm thick part. Deleting a 0.5mm base gasket would drop the squish to about .036" which while still on the fat side, would still be a step in the right direction.

 

[drf255]

They do make a .040 gasket as well.

 

[John Lyngdal]

a .040" gasket is the same as a 1.0mm gasket.

 

[drf255]

a .040" gasket is the same as a 1.0mm gasket.

Yes.

I'm simply pointing out that you may indeed have the fat gasket. The shortblock of your saw may certainly be all 026, but the confusion continues here.

Late 026/260 can have about .016 squish with no gasket, but your jug is early 026 with no casting for the decomp plug. Early ones usually come in around .009 squish with no gasket.