Fixing a major oil leak in the McCulloch EM250 chain saw
My EM250 chainsaw had a serious oil leak. So, I decided to repair it
myself. First, I had to buy a tamper proof screwdriver set in order to
take the chainsaw apart. (There were two tamper proof screws securing
the two halves of the yellow plastic shell together.)
After taking it apart, I discovered that the plastic hose from the oil reservoir tank had broken into many pieces. I also discovered what appeared to be a small oil filter inserted into the outlet of the oil tank; and the filter had a metal fitting for the plastic hose. From the oil tank, the plastic hose disappeared underneath the flywheel.
I then removed a retaining ring and a big washer and removed the flywheel. Under the flywheel, there was a small spring loaded oil valve or oil pump. (I think it is an oil valve that opens or closes as the flywheel comes up to speed thus allowing the flow of oil to the chain. I think the flywheel moves along its shaft to open or close the valve. The spring loaded shaft of the oil valve is in direct contact with the back side of the flywheel. I don't think it is an oil pump because there is not enough movement of the flywheel along its shaft to perform as an oil pump.)
From the oil valve, another plastic hose (also broken in many pieces) is
routed to the back side of the chain saw where the hose plugs into a
fitting. As oil enters this fitting, the oil goes through a small
channel in the black plastic base and comes out through a small hole
where the oil goes into the guide rail for the chain. The guide rail
must be aligned properly with this small hole.
To replace the broken plastic hose, I used small rubber tubing (approximately 1/4" OD). I did not use the oil filter with the rubber tubing; I just inserted the tubing through the small hole in the bottom side of the oil tank. I had to cut two separate pieces of tubing to fit; one from the tank to the oil valve, and one from the valve to the fitting on the back side of the chainsaw. To install the second piece of tubing, I had to take the chainsaw guts out of the yellow plastic housing. (Be careful as you remove the various parts; take pictures to help you remember where the parts go. And save all parts removed for later installation.
After putting the chainsaw back together, be sure to adjust the tension on the chain according to the manufacturer's recommendations. Use the tension adjustment screw at the base of the guide bar.
To understand the principle of how a chainsaw oiler works (in general terms), I recommend this YouTube video:
http://www.youtube.com/watch?v=kmUkieIP-vw
After taking it apart, I discovered that the plastic hose from the oil reservoir tank had broken into many pieces. I also discovered what appeared to be a small oil filter inserted into the outlet of the oil tank; and the filter had a metal fitting for the plastic hose. From the oil tank, the plastic hose disappeared underneath the flywheel.
I then removed a retaining ring and a big washer and removed the flywheel. Under the flywheel, there was a small spring loaded oil valve or oil pump. (I think it is an oil valve that opens or closes as the flywheel comes up to speed thus allowing the flow of oil to the chain. I think the flywheel moves along its shaft to open or close the valve. The spring loaded shaft of the oil valve is in direct contact with the back side of the flywheel. I don't think it is an oil pump because there is not enough movement of the flywheel along its shaft to perform as an oil pump.)
To replace the broken plastic hose, I used small rubber tubing (approximately 1/4" OD). I did not use the oil filter with the rubber tubing; I just inserted the tubing through the small hole in the bottom side of the oil tank. I had to cut two separate pieces of tubing to fit; one from the tank to the oil valve, and one from the valve to the fitting on the back side of the chainsaw. To install the second piece of tubing, I had to take the chainsaw guts out of the yellow plastic housing. (Be careful as you remove the various parts; take pictures to help you remember where the parts go. And save all parts removed for later installation.
After putting the chainsaw back together, be sure to adjust the tension on the chain according to the manufacturer's recommendations. Use the tension adjustment screw at the base of the guide bar.
To understand the principle of how a chainsaw oiler works (in general terms), I recommend this YouTube video:
http://www.youtube.com/watch?v=kmUkieIP-vw
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Thanks much for this posting. I have the same issue and am in the process of repairing it. Questions: a) What is the correct ID and OD of the oil tubing; b) what prevents oil from leaking from the insertion hole on the oil tank?
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