Hey Guys,
I'm starting to tear down an 070. The saw came to me dirty but in pretty good condition overall. The previous owner was a small engine shop owner. I'm unsure what he did to the saw. Something is not adding up so I wanted to give a detailed post so you guys can comment and let me know if this is normal or if you agree something doesn't seem right. Bear with me as this the first thread I've started on the new AS!
I like to give old saws I have no history on a good once over before I try to start them. I pulled the muffler and carb to inspect and then plug in order to do a pressure and vacuum check. I could see scoring on the center of the piston on the exhaust side. When sealed up the saw held 0.5 bars vacuum for over a minute and 10 psi for several minutes as well. I rebuilt the carb and started cleaning/ inspecting everything before pulling the cylinder. I didn't find anything out of the ordinary in the carb or gaskets between carb and cylinder. Nothing to suggest air leak or lack of fuel filter etc.
Exhaust side of piston. Could barely see scoring at sides of exhaust port with cylinder still installed. The center scoring was clearly visible with the cylinder installed. There are some pretty deep score marks on the piston in all areas.
Intake Side of piston. Scoring at sides of intake port. Almost not noticeable with cylinder still installed. No sign of dirt in carb. The fuel filter looks newer style and is intact. The Tillotson HL carb was probably rebuilt within the last 10 yrs or so. The gaskets were similar to the new kit I installed and were in decent shape.
Intake side of piston, clutch side. Scoring aligned with ring pin.
Intake side of piston, flywheel side. Scoring aligned with ring pin.
Mahle 58mm cylinder with heavy machining or sanding lines. The inside of the cylinder was hard to photograph. The surface was dark in areas and shiny in others. Normally the metal transfer areas are the only dark areas. There were well defined dark rings around the ports. I'll try to add a decent pic to the next post.
I checked ring end gap. It varied from 12 to 16 thou depending on the ring and where I measured. Worst was 16 thou for the top ring when I used the piston to move the ring to the centerline of the exhaust port. I couldn't get the ring any higher without taking out the wrist pin.
The rings were marked "ELKO f2"?? Or "ELKO FZ"?? Could these be aftermarket rings?
So what do you think caused this? And where do I go? I have a saw that seems to hold air but has a dead piston and a cylinder that has multiple dark spots (Nikasil removed??). I'm a bit nervous about changing out the top end without finding the problem. I'm thinking the small engine shop owner fixed the air leak, honed up the cylinder (too much), used the old piston and rings and put it back together.
As a side note, the cylinder measured 57.89mm at base. The piston ranged from 57.83 to 57.88mm. All just simple vernier measurements.
Thanks in advance for any insight.
I'm starting to tear down an 070. The saw came to me dirty but in pretty good condition overall. The previous owner was a small engine shop owner. I'm unsure what he did to the saw. Something is not adding up so I wanted to give a detailed post so you guys can comment and let me know if this is normal or if you agree something doesn't seem right. Bear with me as this the first thread I've started on the new AS!
I like to give old saws I have no history on a good once over before I try to start them. I pulled the muffler and carb to inspect and then plug in order to do a pressure and vacuum check. I could see scoring on the center of the piston on the exhaust side. When sealed up the saw held 0.5 bars vacuum for over a minute and 10 psi for several minutes as well. I rebuilt the carb and started cleaning/ inspecting everything before pulling the cylinder. I didn't find anything out of the ordinary in the carb or gaskets between carb and cylinder. Nothing to suggest air leak or lack of fuel filter etc.
Exhaust side of piston. Could barely see scoring at sides of exhaust port with cylinder still installed. The center scoring was clearly visible with the cylinder installed. There are some pretty deep score marks on the piston in all areas.
Intake Side of piston. Scoring at sides of intake port. Almost not noticeable with cylinder still installed. No sign of dirt in carb. The fuel filter looks newer style and is intact. The Tillotson HL carb was probably rebuilt within the last 10 yrs or so. The gaskets were similar to the new kit I installed and were in decent shape.
Intake side of piston, clutch side. Scoring aligned with ring pin.
Intake side of piston, flywheel side. Scoring aligned with ring pin.
Mahle 58mm cylinder with heavy machining or sanding lines. The inside of the cylinder was hard to photograph. The surface was dark in areas and shiny in others. Normally the metal transfer areas are the only dark areas. There were well defined dark rings around the ports. I'll try to add a decent pic to the next post.
I checked ring end gap. It varied from 12 to 16 thou depending on the ring and where I measured. Worst was 16 thou for the top ring when I used the piston to move the ring to the centerline of the exhaust port. I couldn't get the ring any higher without taking out the wrist pin.
The rings were marked "ELKO f2"?? Or "ELKO FZ"?? Could these be aftermarket rings?
So what do you think caused this? And where do I go? I have a saw that seems to hold air but has a dead piston and a cylinder that has multiple dark spots (Nikasil removed??). I'm a bit nervous about changing out the top end without finding the problem. I'm thinking the small engine shop owner fixed the air leak, honed up the cylinder (too much), used the old piston and rings and put it back together.
As a side note, the cylinder measured 57.89mm at base. The piston ranged from 57.83 to 57.88mm. All just simple vernier measurements.
Thanks in advance for any insight.
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