Karla
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- Joined
- Aug 17, 2014
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Completely dissassembled the engine today and the entire chainsaw, so I can give all the parts a thorough cleaning and Inspection. Here are the measurements of the new and old piston & piston ring measurements.
Checking Piston ring wear:
1. Check piston diameter at lowest portion of piston skirt (Use micrometer to measure diameter)
2. Check piston ring side clearance (Use feeler gauges and check clearance with ring installed in piston groove)
3. Check piston ring end gap (Use feeler gauges and check cylinder with piston removed but piston ring only installed into cylinder aprox. ½ inch from bottom cylinder edge)
New Piston & Piston ring measurements:
1. Piston diameter = 1.696 “ or 43.0784 mm
2. Piston ring side clearance = .06 mm
3. Piston ring end gap = .05 mm
Old Piston & Piston ring measurements:
1. Piston diameter = 1.692 “ or 42.9768 mm
2. Piston ring side clearance = .03 mm (tighter clearance due to carbon in ring groove)
3. Piston ring end gap = .23 mm (significantly larger end gap due to piston ring wear)
I will have some pictures of the old piston, on my next post. The old piston really doesn't look too bad, however it did have several good score marks on the piston on the intake side, no scoring on the exhaust side (really clean on exhaust side bur one carbon rub mark). The piston score marks align themselves directly with the piston groove locator pin on the intake side. I have heard of those little locator pins coming loose and scoring the cylinder but can't see how it could score the piston. The scoring marks go all the way from the bottom of the skirt, thru the piston ring, and to the top of the piston. I checked the inside of the cylinder but do not see any corresponding scoring marks in the cylinder wall. I will check the cylinder again tomorrow when I start cleaning up the parts. There is some varnishing of fuel oil inside the cylinder transfer channels but I have not removed the transfer channel covers as of yet, maybe tomorrow. Oh all of the chainsaw parts look good so far but everything really needs a thorough cleaning, The brake handle does have about 1/2" crack thru one side of the handle but can be easily repaired. Maybe I will epoxy that tomorrow too, and then it wil be onto reassembly. I also verified that the fuel tank vent is connected to a vent line that goes to the air cleaner. One of Husqvarna's recomendations were to disconnect the vent hose, unplugging it from the tank vent, and then plugging the vent hose, or buy the special replacement vent hose. Again Not sure how this recommendation will fix a Hot start problem ? All of the bearings look good, and probably won't separate the crankcase or remove the crankshaft, it looks like everything is sealed up good with No leaks. I did remove the flywheel, clutch, and oil pump so I could check for leaks and they really needed a cleaning anyhow. Lol.
Checking Piston ring wear:
1. Check piston diameter at lowest portion of piston skirt (Use micrometer to measure diameter)
2. Check piston ring side clearance (Use feeler gauges and check clearance with ring installed in piston groove)
3. Check piston ring end gap (Use feeler gauges and check cylinder with piston removed but piston ring only installed into cylinder aprox. ½ inch from bottom cylinder edge)
New Piston & Piston ring measurements:
1. Piston diameter = 1.696 “ or 43.0784 mm
2. Piston ring side clearance = .06 mm
3. Piston ring end gap = .05 mm
Old Piston & Piston ring measurements:
1. Piston diameter = 1.692 “ or 42.9768 mm
2. Piston ring side clearance = .03 mm (tighter clearance due to carbon in ring groove)
3. Piston ring end gap = .23 mm (significantly larger end gap due to piston ring wear)
I will have some pictures of the old piston, on my next post. The old piston really doesn't look too bad, however it did have several good score marks on the piston on the intake side, no scoring on the exhaust side (really clean on exhaust side bur one carbon rub mark). The piston score marks align themselves directly with the piston groove locator pin on the intake side. I have heard of those little locator pins coming loose and scoring the cylinder but can't see how it could score the piston. The scoring marks go all the way from the bottom of the skirt, thru the piston ring, and to the top of the piston. I checked the inside of the cylinder but do not see any corresponding scoring marks in the cylinder wall. I will check the cylinder again tomorrow when I start cleaning up the parts. There is some varnishing of fuel oil inside the cylinder transfer channels but I have not removed the transfer channel covers as of yet, maybe tomorrow. Oh all of the chainsaw parts look good so far but everything really needs a thorough cleaning, The brake handle does have about 1/2" crack thru one side of the handle but can be easily repaired. Maybe I will epoxy that tomorrow too, and then it wil be onto reassembly. I also verified that the fuel tank vent is connected to a vent line that goes to the air cleaner. One of Husqvarna's recomendations were to disconnect the vent hose, unplugging it from the tank vent, and then plugging the vent hose, or buy the special replacement vent hose. Again Not sure how this recommendation will fix a Hot start problem ? All of the bearings look good, and probably won't separate the crankcase or remove the crankshaft, it looks like everything is sealed up good with No leaks. I did remove the flywheel, clutch, and oil pump so I could check for leaks and they really needed a cleaning anyhow. Lol.