Cleaning of Engine Parts Should Always be Practiced During Engine Overhaul and Disassembly

When you remove the engine cover to replace the clutch disc or change the oil filter, have you ever taken a peek inside the engine and been surprised? Most of the engine parts are cast aluminum parts. So, they are supposed to look like the "silver" color of the aluminum surface. However, the inside of the engine I looked at was sooty and almost completely black. This is thought to be oil stains accumulated from the engine oil. If the engine is so black, the functional parts inside must be black as well. If the engine is in good functional condition, it's fine, but if you have to disassemble it, or if you just can't stop thinking about it, you should completely disassemble the engine, inspect each functional part, and clean the dirty parts as much as you can.

The interior of the engine gets dirty without even knowing it.

For example, the engine that you bought at the internet auction or garage sale. However, there must be many Sunday mechanics who have experienced that the inside of the engine is dirty and black. It's not just the external dirt from oil leaks and oil seepage, but also the dirt from neglecting to change the engine oil, which makes you wonder about the internal condition of the engine.

So, I disassembled the engine into pieces, and the contents were amazingly black. After disassembling, the crankcase which became a single item was as you can see. Both inside and outside were literally "pitch black" by the dirty and burnt engine oil.

Dirty parts are cleaned with Hanasaka G Multi Cleaner

The Hanasaka G Multi-Cleaner from Sakae Giken, a company known for its Hanasaka G brand, is a powerful cleaner that can be used to remove dirt from the plastic exterior parts of motorcycles as well as various parts of the engine. It can be diluted 3 to 30 times with tap water depending on the degree of contamination. It is a water-soluble degreasing cleaner that can be used with lukewarm or room temperature water. It is not fire-retardant, so it does not ignite, and it has no odor or irritation characteristic of solvents. It is known as a degreasing cleaning agent that is gentle on bare hands and environmentally friendly. It is also easy to use when rinsing, as it does not produce a lot of foam-like ordinary neutral detergents.

Diluted cleaning agent in a pail

When cleaning the exterior and undercarriage parts of the vehicle, prepare a spray bottle and pour in the original Multi-Cleaner solution, then pour in lukewarm water to dilute the original solution. When you want to clean the persistent oil stains around the engine, it is effective to dilute the solution 3 to 5 times with lukewarm water. In the case of a black engine like this one, it is better to put the Multi-Cleaner undiluted in a pail and pour hot water from the hot water heater into the pail for soaking. This time, we decided to dilute it with about 8 times hot water and use it.

Spray cleaning is possible for light oil stains

If you want to remove light oil stains, put the diluted multi cleaner in a spray bottle and spray it on the stains, then scrub the stains with a sponge for exterior and a hard nylon brush for engine parts. After degreasing and washing, rinse thoroughly with tap water. When cleaning the engine parts, put the multi cleaner in a container and dilute it with tap water. It is better to use a brush to degrease and wash in the container. After cleaning, blow air and dry the parts on a newspaper. If you have a compressor, you can use an air gun to blow off the water with compressed air.

If it's badly stained, you can soak it in a pail and leave it for a while.

This time, because the crankcase is too dirty, I put the cleaning solution diluted 8 times with hot water in a pail, and submerge the crankcase in the cleaning solution and leave it. The crank case is submerged in the solution and left. I left the crankcase in the solution for a few days, brushed it and left it again. At first, the diluted solution of multi cleaner was pale milky white, but it gradually turned black. You can imagine the cleaning effect from the stain of this cleaning liquid.

Additional hand polishing, as you can see.

It took a few days of repeated soaking in Hanasaka G multi cleaner. After the carbon stains were roughly removed, I added a final hand polish and this is how beautiful it turned out. Even if you don't have the facilities or equipment for wet blasting, it is possible to remove the dirty stains if you want to. This kind of work is the experience of a Sunday mechanic, and it will be used in the future. Finally, the motorcycle was degreased again with neutral detergent, and after air blow, it was ready for assembly.

If you continue to leave a dirty engine, it will be difficult to do the cleaning work afterwards. When you notice an oil leak or oil seepage, immediately wash off the dirt with a cleaning spray (solvent) such as parts cleaner or brake cleaner, and after confirming degreasing, use a high-performance chemical such as Leak Repair to harden the affected area from the outside to prevent the leak or seepage from recurring. However, it should be noted that if you continue to leave such dirt = oil seepage, whether you know it or not, it will be very difficult to remove the dirt later on. In particular, the dirt around the cylinder head where the temperature is high will cause the engine oil to burn and stain, so it is best to clean it as soon as possible.

The crankcase presented here must have been dirty like this as a result of riding without any maintenance. Why did it become dirty like this? The following is only my imagination, but I think it is the correct answer.

The engine has probably been traveling for more than 10,000km without any oil change. The piston rings and cylinder sleeves must have exceeded their wear limits as a result of traveling the engine for so long despite the fact that the engine oil performance has deteriorated significantly. The next thing that happens when the wear limit is exceeded is a drop in compression pressure. The exhaust gas from the explosive combustion is released into the atmosphere after passing through the open exhaust valve, exhaust port, exhaust pipe, and muffler. However, when piston rings and cylinders reach their limit of wear, the combustion gases cannot be kept airtight after the explosion. As a result, combustion gas enters the crankcase through the gaps in the piston rings and ring mating ports.

The dirty engine oil then enters the combustion chamber through the gap between the cylinder and piston rings, and the explosive combustion process is repeated. The repeated operation of the 4-stroke engine causes a large amount of blow-by gas to enter the crankcase. The blow-by gas would have caused the engine oil to become contaminated, which in turn would have turned the engine black.

The engine must have been blowing a lot of white smoke from the exhaust system as well. As a result, the power of the engine was significantly reduced and the engine had to be replaced. Or the engine was dismantled and we bought the complete engine. In any case, when you reuse such dirty engine parts, you have to clean each parts well.

Here, we have practiced the cleaning process using the crankcase as an example, but why is such cleaning necessary? The reason is that if the parts are reused with dirty engine interior, even if new engine oil is put in, the engine oil will get dirty faster. By disassembling each unit part as much as possible and then removing the dirt, the black internal parts will regain their beautiful shine.

When overhauling a blackened engine, not only inspecting and replacing major parts such as pistons and piston rings but also disassembling the clutch housing into individual parts and thoroughly cleaning them will make the internal parts more beautiful than you can imagine. If you come across such an opportunity, we would like you to practice it.