Things You'll Need:
- Find part number and go to a lawnmower shop and get the rings. Id recomended a new crankcase gasket as well. You will need a ratchet tool and bits and possibly a drill with drill bits.
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Step 1
Remove the lawnmower blade and all parts supporting the blade. Also drain all oil from mower using oil plug found under mower. You might have trouble removing the metal piece that supports the blade. I had to drill it off but becareful because it needs to go back. You cant open the engine with it on the crankshaft so make sure nothing is on the crankshaft after.
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Step 2
Remove the top cover connecting the pull rope to the top of the crank shaft exposing the magneto. Also remove gas tank.
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Step 3
Remove the engine from the body by loosening the bolts on the bottom of the body. Open the cylinder piece where the spark plug is exposing the piston and valves. This gasket can be reused so dont buy a replacement.
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Step 4
Turn engine upside down start removing the bolts holding the bottom piece to the upper piece. It is possible to use the same gasket if you are careful and dont break it.
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Step 5
To remove the bottom piece you might have to turn the crankshaft untill the bottom piece comes off all the way set it aside.
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Step 6
Now the inside is exposed. The gear connected to the crankshaft is for the timing and should be left inside but if needed will have to be removed. Their is another piece on the top of the timing gear becareful not to loose it.
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Step 7
Locate the piston rod connected to the crank shaft by 2 bolts. Remove the 2 bolts and set them aside along with the other half of the piston rod piece. Now remove the piston by pushing it out of the cylinder. Do not remove the piston rod from piston because it makes more work.
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Step 8
Note how the old rings are installed. Carefully remove the old rings and check for cylinder wall damage fine scratches are ok. Start with the bottom ring the lubricationg ring and put the other springy piece on first then carefully work the lubricating ring on the piston. Now carefully apply the other 2 rings to the piston working from bottom to top.
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Step 9
Now the fun part put the piston back in the cylinder. With a cloth rub clean oil on the entire cylinder wall. I just push them in one at a time. You can get a tool to compress them because they expand. Tighten the rings with fingers and push them into the cylinder one at a time. Next line up the piston rod and reconnect to the crank shaft with the 2 bolts make them tight but dont break the rod.
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Step 10
If you need to fix the timing thats kind of easy but requires concentration. First note what way the crank shaft rotates when you pull the rope. Then set the piston up as if it is compressing the mixture. Bring it down slightley make sure it will push the crank shaft the correct way turning it the same direction the rope does when you pull it. Next continue slowly bringing piston down untill it is about to come back up. Take the timing gear and make sure the exhaust valve opens when the piston starts coming back up. Then carefully check after exhaust valve closes and piston starts going down and make sure the intake valve opens then closes when piston is about to come back up. This time no valves should open untill the piston comes up to compress then goes down powerstroke. When it starts to come up the exhaust valve should open. If all is good the timing is correct. Replace the gasket with new or use the old one not ripped or broken and make sure everything is in place and lines up you might need to turn the crank shaft again to get the cover to go on. Dont move or adjust the timing gear again. Start tightening the bolts hand tight securing the bottom cover. Replace the piston cover. You can watch piston movement to double check timing if you wish, before replacing cover.
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Step 11
Reattach engine to body. Put new oil to proper level. Then attach the top cover again. Attach blade and parts. Gastank. Reconnect to carb and try to start. Might need starting fluid and lots of pulling. Check for exhaust indicating good compression and proper timing. My mower took lots of adjusting to get it working after i canged the rings. Take you're time with this so you wont have to reopen the mower as many times as i did.
