I just got finished getting an OEM 038M cyl to fit on a 038S case.
The base of the cyl has enough room on the case so no grinding of either was needed to clear the case. I WAS concerned about this because Stihl mentioned that grinding the case was sometimes necessary when fitting a 038S cylinder on a 038 case (NOT what I’m doing here but similar). This is the first one of these I’ve done so keep it in mind, it MIGHT not be a general theme......
The bolt pattern is a little tighter on the 038S than the 038M, more so front to back than side to side. Thus you need to grind (slot) the holes at an angle as the hole differences are greater apart front to back than side to side (e.g. not 45o}. I ground the slots for each hole by ca. 0.045” (front to back) and ca. 0.025” (side to side). There are still plenty of surfaces between the slotted holes and the bore (0.20”) for the base gasket to get a good seal (stock for a 038M was ca. 0.25”).
The outside cyl area just above where the bolts seat also needed to be ground back to allow the bolt heads to clear the cyl when being screwed in. I did this by grinding, and the slotting of the bolt holes, with a Dremel tool and carbide bits.
In one of the four holes it was difficult to get the T27 torx driver through the cylinder fins and into the bolt head. I opened up all the holes through the fins slightly with a 7/32 file (readily available! you can speed this up by chucking it in a drill or just drill them out if you have a drill press).
I did not do this work, at work, so a Bridgeport to slot the bolt holes/drill, would have been nicer, but is not needed. You really just need a Dremel and proper bits to take back the cyl surface (vertical surface that interferes with bolt heads screwing in) so the bolts can seat against the cyl base and to the slot the holes themselves, a 7/32 file will fix the T27 torx clearance, slot the holes (base at the cyl/case) with the Dremel.
In fact you NEED the Dremel to get the bolt heads to fit. One more thing, a dial caliper (0.01”) to compare/measure original cyl holes to where you grind the slots. It’s about a 2:1 ratio length (front to back) to width (side to side) that you take in grinding the slots. No rocket science here! The cylinder now bolts right on!!!
P.S. sorry I don’t have pictures. It’s not together yet as am putting together the odds and ends for a good work saw (i.e. ground the bar rails level/square at work using the 90o belt grinder (nice but abused 20” Sthil ES bar……). I will when I can then compare this with another conversion using the Tecomec 038M cyl assy. On another 038S……
P.P.S. When I do get pics it won’t be a “pretty boy saw” , e.g. all painted all up and you can eat off it…….I’m going to work it!, all internal will be spotless before assemble though. Best M.P.!!!
The base of the cyl has enough room on the case so no grinding of either was needed to clear the case. I WAS concerned about this because Stihl mentioned that grinding the case was sometimes necessary when fitting a 038S cylinder on a 038 case (NOT what I’m doing here but similar). This is the first one of these I’ve done so keep it in mind, it MIGHT not be a general theme......
The bolt pattern is a little tighter on the 038S than the 038M, more so front to back than side to side. Thus you need to grind (slot) the holes at an angle as the hole differences are greater apart front to back than side to side (e.g. not 45o}. I ground the slots for each hole by ca. 0.045” (front to back) and ca. 0.025” (side to side). There are still plenty of surfaces between the slotted holes and the bore (0.20”) for the base gasket to get a good seal (stock for a 038M was ca. 0.25”).
The outside cyl area just above where the bolts seat also needed to be ground back to allow the bolt heads to clear the cyl when being screwed in. I did this by grinding, and the slotting of the bolt holes, with a Dremel tool and carbide bits.
In one of the four holes it was difficult to get the T27 torx driver through the cylinder fins and into the bolt head. I opened up all the holes through the fins slightly with a 7/32 file (readily available! you can speed this up by chucking it in a drill or just drill them out if you have a drill press).
I did not do this work, at work, so a Bridgeport to slot the bolt holes/drill, would have been nicer, but is not needed. You really just need a Dremel and proper bits to take back the cyl surface (vertical surface that interferes with bolt heads screwing in) so the bolts can seat against the cyl base and to the slot the holes themselves, a 7/32 file will fix the T27 torx clearance, slot the holes (base at the cyl/case) with the Dremel.
In fact you NEED the Dremel to get the bolt heads to fit. One more thing, a dial caliper (0.01”) to compare/measure original cyl holes to where you grind the slots. It’s about a 2:1 ratio length (front to back) to width (side to side) that you take in grinding the slots. No rocket science here! The cylinder now bolts right on!!!
P.S. sorry I don’t have pictures. It’s not together yet as am putting together the odds and ends for a good work saw (i.e. ground the bar rails level/square at work using the 90o belt grinder (nice but abused 20” Sthil ES bar……). I will when I can then compare this with another conversion using the Tecomec 038M cyl assy. On another 038S……
P.P.S. When I do get pics it won’t be a “pretty boy saw” , e.g. all painted all up and you can eat off it…….I’m going to work it!, all internal will be spotless before assemble though. Best M.P.!!!
