| Lawnmower Engine Repair -- Engine Disassembly |
From "Weekend Mechanic"
episode WKM-104 |
|
|
|
advertisement
|
With the engine removed from the riding lawnmower, the external engine components can be removed to get to the heart of the problem -- the internal combustion chamber. Engine Disassembly - Unbolt and remove the upper engine housing (figure A).
- Unbolt and remove the muffler (figure B).
- Unbolt and remove the carburetor.
- The next external component to come off is the flywheel. The bolt that secures the flywheel (figure C) is installed extremely tightly. For this particular engine, the torque spec for this bolt is 65 foot-pounds. Some special procedures are required for safely removing the flywheel.
- Since the flywheel can rotate with the crankshaft, install a strap-wrench around the flywheel (figure D) to hold it steady as the bolt is loosened and removed.
- Using a long-handled wrench for plenty of leverage, loosen (figure E) and remove the flywheel bolt.
- With the flywheel bolt removed, loosen and remove the bolts that secure the fan (figure F).
- Important: To remove the flywheel from the crankshaft, a specialized tool known as a flywheel puller is required. Removing the flywheel without this tool could cause damage. A flywheel puller is an inexpensive tool, costing about $5.
- With the fan bolts removed, attach the flywheel puller into the bolt-holes and tighten the bolts to loosen the flywheel (figure G).
- With the flywheel loosened, remove the puller and carefully lift off the flywheel (figure H).
- With the flywheel removed, the engine can be stripped further. Begin by loosening the alternator retaining bolts and removing the alternator (figure I).
- Next, remove the coil (figure J).
- Flip the block upside down on the work surface to access the oil pan. Unbolt and remove the oil pan (figure K).
- With the oil-pan removed, unbolt and remove the cylinder head.
- Remove the cam shaft.
- Remove the valves (figure L).
- Disassemble and remove the piston-rod assembly (figure M).
- Carefully lift out the crankshaft (figure N).
- Finally, remove the piston and piston rod from the engine cylinder. If it needs some loosening, tap the piston gently with a non-metal hammer (figure O ).
- With the engine disassembled, the inside of the cylinder can be checked for wear to determine what kinds of repairs will be required. A telescoping gauge is the best tool for measuring the cylinder bore to determine the extent of engine wear.
- To use the telescoping gauge, cock the spring mechanism, lock the gauge indicating the diameter of the bore (figure P), and gently rotate the gauge out.
- With the telescoping gauge removed, use a dial caliper obtain the exact bore measurement (figure Q).
Our measurement indicated that the bore was significantly worn. To refurbish the engine, the cylinder will need to be re-machined to increase the size of the bore. An oversized piston will then be used to replace the old one. In the segment that follows, the re-machined engine will be re-assembled and outfitted with the necessary replacement parts. Weekend Mechanic Factoid : The average life of a lawnmower engine ranges from 500 to 1,500 hours of use.
RESOURCES :
The Haynes Small Engine Repair Manual
ISBN: 1850106665
Author: Curt Choate, John H. Haynes
Haynes Publishing Group
Chilton's Small Engine Repair Up to 20 Hp
Model: 0801983258
Author: Kerry A. Freeman
Nichols Publishing
Small Gas Engine Repair
Model: 0830641424
Author: Paul "How to Troubleshoot" Dempsey
| 
)
)
)
)
)
)
)
)
)
)
)
)
)
)
)
)
)
