Pay Attention to Engine Oil Management and Take Extra Care Right After Engine Repair

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It is easy to dismiss old motorcycles with the cliché "it's an old motorcycles, it's just like that ......", but with proper maintenance, you can enjoy a normal motorcycle life. Old motorcycles with a lot of troubles are often poorly maintained or have been subjected to "misguided maintenance". If the engine is in good condition (4-stroke engine for example), the most important thing to pay attention to is the oil change, oil filter change, and air filter condition. There are surprisingly many things that can be noticed during such work, so don't underestimate the importance of maintenance.

Engine just after overhaul above waist

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An engine that has been ridden for many years will have symptoms such as white smoke blowing from the muffler. This is an indication that the piston rings and pistons are worn to the point where the clearance is excessive, causing the "oil to rise". There are also many cases where the piston rings lose tension and are unable to scrape off the oil. On the other hand, if the cap seals on the intake and exhaust valve stems are worn or deteriorated and cannot fully seal the engine oil, the oil will drop. This also causes white smoke to be blown from the muffler. When the oil drops, the engine tends to emit white smoke when downshifting. We installed new oversized pistons (for the Kawasaki Z1), cut and aligned the intake and exhaust valve seats in the cylinder head, and replaced the valve stem seals. After the repairs were completed, the motorcycle was under break-in operation. Even if you don't see any white smoke, you can still get an idea of the engine condition by measuring the compression pressure.

Be careful of old oil that flows out.

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Immediately after an engine repair or assembly, it is best to practice an oil change as soon as possible, including cleaning the inside of the engine. If it's a new or an older motorcycles, there is no need to change the oil, but if it's an old motorcycle, it's hard to predict what will happen, and you want to change the oil as soon as possible regardless of the engine repair. This time, the engine oil and the oil filter were changed at about 50km after the engine overhaul. The molybdenum grease that was used during the engine overhaul can be seen on the stock drain with magnet.

Take care of it with the well-established Motorex products.

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Although 100% synthetic low-viscosity oils are attractive, for an older air-cooled engine and an air-cooled Z that is mainly used for city driving, we used a standard viscosity index 10W-40. In this case, we used Motrex Top Speed 4T. The engine oil capacity of the Kawasaki Z1 and Z2 is approximately 4.5 liters. Motorex Top Speed 4T 10W-40 is refined using Motorex's proprietary molecular conversion process, and its main feature is that it is a high-grade mineral oil that is close to 100% synthetic oil.

Attractive high-performance oil filter

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Daytona, the Japanese domestic distributor of Motorex products, offers a lineup of high-performance oil filters. Fortunately, they also had one for the Kawasaki Z1 and Z2, so I took advantage of it. The main feature of this filter is that the fold of the filter paper has been increased by about 20% compared to the genuine Kawasaki oil filter, increasing the filtration area.

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The drain plug, as well as the O-ring for the oil filler case drain, should be replaced when the oil is changed. In the days of the first generation Kawasaki air-cooled Z, the O-ring was not an aluminum gasket washer or a crush gasket washer, but an easy to replace O-ring. In this case, the O-ring was not crushed, so it was reused.

Visible maintenance

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A compression gauge is necessary to measure compression data. The numerical data varies with each engine model, but comparing the measured values before and after will help you understand the importance of maintenance. Using a 4-stroke motorcycle engine as an example, if the measured data is 6 to 7 kgf/cm2 (now often indicated in MPa), the compression pressure is considered to have dropped considerably.

Surprised at the difference in data after overhaul!

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When the engine was stock, the data was 9kgf/cm2, but after the overhaul, with the use of the Z1 crank, the data changed significantly to just under 13kgf/cm2. If the data is different for one cylinder, it means that there is some kind of problem or difference in that cylinder. The increased compression makes for an overwhelmingly torquey ride! The motorcycle accelerates nicely without increasing engine speed. In a sense, the engine is more durable because it does not need to be revved as much, which reduces wear and tear on the engine parts. This engine tuning and power-up has various meanings and purposes, and is not simply a pursuit of speed.

 
POINT
  • Point 1: After the overhaul of the engine, let's change the oil and oil filter as soon as possible.
  • Point 2: 100% synthetic low-viscosity oil is attractive, but there is also a reason to dare to choose high-performance mineral oil.
  • Point 3: When you change the oil, replace the drain gasket with a new one!
  • Point 4: Let's make good use of the compression gauge that can check the engine condition with eyes.
  • Point 5: If you use a compression gauge for before and after maintenance, you can see a clear difference.

 

Not only the full overhaul of the engine but also when the repair or the replacement of the parts in the engine is practiced such as the disassembly repair of the engine, the clutch overhaul, etc., it wants to keep in mind the oil change as soon as possible. The number of oil changes immediately after maintenance can be saved by laying the motorcycle body down so that the engine oil does not flow out before maintenance. It is ideal to be able to change to new oil even in a small mileage. However, it is the Sunday mechanic who does the maintenance with the idea because there is the situation of the pocket, too.

The Kawasaki air-cooled Z maintained here has been overhauled, including the engine paint. At the same time, the engine was also tuned to increase power. After overhauling the engine, we took it for a test drive around the neighborhood (it would be too sad to go out for a long drive and have a heck of a ruckus), and after riding about 50km, we changed the engine oil. I cleaned every single part when I disassembled the engine, so I think the inside of the engine is completely clean. I would like to recommend you to change the oil as soon as possible, not only for the overhaul of the engine waist or the full overhaul of the complete engine, because there are some dirt left in the parts that I did not notice even if I think so.

The engine oil used was Motrex Top Speed 4T (viscosity: 10W-40), which is popular among fans of old and out-of-print motorcycles. In terms of reducing friction loss and eco-friendliness, the low viscosity oil that has been popular in recent years is very appealing, but when used in old motorcycle models, oil seepage tends to occur due to the gasket material and clearance settings. On the contrary, it is the evidence that confirms the "high permeability" of the high-performance low viscosity engine oil.

On the other hand, this oil is characterized by the fact that it uses mineral oil as its base oil and undergoes molecular conversion. Natural mineral oil has a non-uniform molecular structure, but Motrex's unique molecular conversion technology has homogenized this molecular structure to create a molecular arrangement that is as close as possible to that of 100% synthetic oil, which is its greatest feature. We chose Top Speed 4T's 10W-40 and wanted to enjoy the life of an old motorcycle.

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