Disassembling an engine is performed in the following format:
– Remove any clutches and pulleys off of the crankshaft
– Drain the oil from the engine
– Remove the blower housing by loosening the three bolts that hold the blower housing in place. (Typically the three bolts are mounted in the lower section by the blower and one in me cylinder head.)
Note: it is not necessary at this point in time to remove the flywheel. Typically the flywheel only needs to be removed if the crankshaft has been damaged excessively.
– Remove the cylinder head bolts. Typically there about seven or eight cylinder head bolts. Be sure to keep the cylinder head bolts in the head and placed in a secure place. Note: putting the wrong cylinder head bolts on the engine or putting the improper bolts in the wrong hole hole locations can cause stripping of the head. Care and attention must be given to make sure that the correct bolt lengths are used.
– Remove the end case bolts. Typically there are about 8 to 10 bolts holding the end case or site cover on me and engine block.
Note: typically the end cover will not just pop off because it is being held by the crankshaft bearing and the end seal on the crankshaft. Careful prying and light tapping of the end case may be needed to remove it from the crankshaft. If any prying is to be performed to use three screwdrivers, not two and not one. The reason for this is that prying the cover can cause damage to the seal and to the seal faces when prying into the crack between the crank case and the cover. It is more viable to lightly tap using a block of wood and a hammer on the side of the oil filler section.
On vertical engines sometimes the end cover can be removed by holding the flanges on the end cover and have someone lightly tap the crankshaft with a block of wood. Be very careful when doing this and make sure the engine has a place to drop into such as a bucket of rags, otherwise damage will occur to the engine when it drops.
Be aware that the end cover can suddenly release when it is being pried loose.
– Gently remove the end cover from the engine. Be aware that the camshaft may fall out of place and come out of the engine of suddenly. Be prepared for oil spillage and for the tappets to fall inside the engine case.
– Remove the camshaft and the tappets.
– Loosen the connecting rod bolts and remove the connecting rod cap.
Note: the edge of the bore on the engine should be scraped clean using a fine piece of sandpaper. The purpose for this is that the edge of the bore can have excessive carbon buildup on it. If this is not removed it can score the pistons. So, the removal of this residue is recommended.
– Gently slide the piston up and out of the bore by pushing on the bottom of the connecting rod with your finger.
– Examine the bore for score marks and for excessive wear on the bore. Typically in order to get an accurate assessment of the bore a micrometer type tool will be needed. Since most of us don’t have those kind of tools a preliminary observation of the bore can be performed before the piston is taken out of the engine. The piston can be slid side to side inside the bore and this will give you an assessment of how much slop there is inside the bore.
– If the connecting rod had score marks on it, the crankshaft will need to be removed. The flywheel can be removed at this time, and then the crank shaft can be slid out. (On engines with points care must be taken to remove the points system, otherwise the point activator can be damaged when the crank is removed. It will get caught and shear off a portion of the activator mechanism)
The crank journal typically will have imbedded material on it from the connecting rod. This will need to be sanded off using a very, very fine sand paper (emery cloth, like a finger nail file) and gently remove any aluminum residue. This can be accomplished readily by feel. If there is any bump feelings, the surface is not clean enough. Your finger can feel the surface irregularities.
– Remove the carburetor and access the valve retainers by removing the PVC valve. Typically two screws hold the PVC valve in place.
- Remove the valve retainers. There are typically two types, the two piece type and the single retainer type. Both can be removed by holding down on the valve and using two screw drivers (or a needle nose plyers) push up on the retainer by prying down. The retainers will then be able to come loose. It does take some doing and patience is required. Be sure not to scrape the side of the valve stem.
- Take a file and gently remove the bur off of side of the valve so that it will slide out. Do not force the valve out or you will destroy the valve guide.
- Remove the valve and examine the valve surfaces, both on the engine and the valve itself.
Bottom line, when disassembling an engine remember how all the pieces came off and store them accordingly. If you question whether you are going to put it together properly, then take pictures. With today’s digital cameras you can take instant pictures of almost anything and it is well worth your time.
Assembling the engine has its quirks, especially when putting the piston back in place. Next time we will discuss what to do once you have the engine apart and how to reassemble it properly.