How to Make Your Own Cylinder Base Gasket If OEM Parts Are Not Available

The availability of replacement parts is an important aspect of maintaining a motorcycle. It is best if OEM parts are available, but with older or out-of-print models, the necessary parts may not always be available. Among the gaskets that are essential for engine maintenance, cylinder base and engine cover gaskets may be able to be replaced by your own work.

You can make your own cylinder head gasket, but you can't make a base gasket.

Business sports with underbone frames and horizontal cylinder engines were a category that became so popular that races were held on them. The Suzuki FD125, which is almost never seen in Japan, was given the heroic name of shogun. This vehicle is a mid 2000's model with a carburetor specification.

The cause of the white smoke was that the engine oil could not be scraped off due to the loss of tension in the piston rings. The combustion chamber and pistons were black with carbon from the burnt oil. As for the piston ring, the number of the genuine one was not known, so I substituted the ring of another model from the piston diameter and ring thickness.

When you smell white smoke and burnt oil coming from the exhaust system of a 4-stroke engine, you have to suspect either a rising or falling oil. Whether it is rising oil, which is mainly caused by worn piston rings, or falling oil, which is suspected to be caused by deteriorated valve stem seals, the cause can be identified by removing the cylinder head and cylinder.

If you know the cause of the problem, you can just replace the parts and the problem will be solved. However, there are times when the important parts are not available. It is inevitable that too old parts will be discontinued because motorcycle manufacturers have a retention period for genuine parts. This is because it is not practical to supply genuine parts for all models manufactured in the past indefinitely.

The first to disappear is exterior parts such as cowls and gasoline tanks, as well as parts with color schemes, followed by headlights and taillights, whose designs vary from model to model. On the other hand, parts related to the engine, brakes, and other engine parts are highly available even after many years have passed since the motorcycle itself underwent a model change.

However, there are some parallel imported vehicles that are not officially sold in Japan, and it is difficult to identify the part number itself. In particular, it is not uncommon for small displacement vehicles produced overseas to have no part number in the domestic distribution channel, even if the part number is known.

The underbone frame business sportbike called FD125 that Suzuki sold in Indonesia is one such motorcycle. It was such a rare model that I don't know how many there are in Japan. I tried to search for parts in Japan by referring to the part number in the parts list I found on the internet, but I couldn't find any hits.

In spite of that, oil is spitting out from the exhaust system, so it is inevitable for a tinkerer to try to disassemble and find the cause. At that time, it is an ironclad rule to disassemble the valve stem seals and piston rings that are thought to be the main cause of the problem, while paying attention to the other parts so that they can be reused.

Of course, if the genuine parts are readily available, the gaskets should be replaced without question, but if the part number is unknown, it is not possible. The head gasket is a metal type, so it is easy to remove and can be reused. Even if you use a scraper to remove it from the outer circumference little by little, it will usually cut off somewhere. The older the model, the more pronounced the tendency, and it is not uncommon for the gasket to crack before the scraper blade is inserted.

Even in such a case, a base gasket for a single-cylinder engine is likely to be manageable. If the cut part matches perfectly, it may be possible to restore it by applying a liquid gasket as first aid, or it may be possible to use your own work even if you have disassembled it like a puzzle.

Clean the carbon from the combustion chamber and pistons with a foam type carbon cleaner. A paint stripper spray may also be used. If the temperature is low, the reaction will be slow, so it is better to warm up the parts before spraying in winter.

I sprayed some cleaner and waited for a while, then scrubbed with a wire brush to remove the carbon. There was no need to remove the intake and exhaust valves because the oil was coming from the piston rings, but just in case, I cleaned the backside of the valves and ports, and replaced the valve stem seals. The stock seals were not available, so I used the same parts for the Honda horizontal engine.

Utilize universal gasket sheets for tuning.

Using the stock gasket as a template, I transferred the shape onto a 0.5mm Daytona gasket sheet. When I removed the gasket from the engine, the cam chain tunnel was cut off, so I used an image to connect the lines. If you have more cuts, you can paste it on a thick paper and make a copy.

M6 size stud bolt holes can be cut out with design cutters, but it is difficult to clean up the large holes in the cylinder sleeves freehand, so a circle cutter is prepared to cut out a perfect circle. The compass and circle cutter are also useful for motorcycle maintenance.

The head gasket, which is sandwiched between the cylinder and cylinder head, is made of a metal material to withstand the explosive combustion pressure of the air mixture. The head gasket, which is sandwiched between the cylinder head and cylinder head, is made of a metallic material to withstand the explosive combustion pressure of the air mixture.

The base gasket, on the other hand, is made of a mixture of rubber and fiber called joint sheet, and can be made by cutting it out from the gasket sheet available as a universal product. The thickness of the base gasket on a 2-stroke engine can also be used as a tuning part to change the cylinder port timing and the volume of the primary compression chamber. For this reason, Daytona gasket sheets are available in different thicknesses in 0.1mm increments.

On a 4-stroke engine, neither the primary compression nor the port timing is relevant, so the gasket is used to repair a damaged gasket, but when choosing the thickness, it is best not to differ too much from the stock gasket.

When making a base gasket from a generic sheet, it is easiest and most reliable to use the stock gasket as a pattern. If a part is damaged when peeling it off from the crankcase or cylinder, write that part on the gasket with an image of the original shape. If it comes apart into several pieces, you can reproduce the exact design by pasting it on a piece of cardboard to reproduce the shape, making a copy, and then reflecting the shape on the gasket.

This copying method is also effective in the reproduction of the cover gasket of the left and right side of the crankcase, and the shape of the mating surface can be grasped by pulling out the dowel pin etc. from the cover and placing it directly on the copying machine and copying it.

After scribbling the design onto the gasket sheet, cut it out using scissors, cutters or punches. The key here is to use a blade that cuts well and to work on a hard cutter mat. If you use a soft mat with a blade that is not sharp, the cutting surface will tend to become soggy and you will not be able to reproduce the exact shape.

The role of the base gasket is to prevent oil leakage between the crankcase and cylinder head, and to prevent sinking when tightening the cylinder stud nut, etc. The sealing surface by the gasket is limited, so be careful not to cut it into an inappropriate shape. Especially, it is important to cut out the circle according to the distance between 4 stud bolts and the cylinder sleeve outer diameter, so it is necessary to use a good punch or circle cutter.

It's important to clean off any remaining debris from the engine side before setting the new gasket.

Remove the old gasket from the cylinder and crankcase before installing the new gasket. When using the scraper, be careful not to damage the parts side.

If the stock gasket shape is accurately transferred, a homemade gasket will fit without any problems. The 2 stroke engine is also used as a tuning part to change the port timing by changing the thickness of the gasket. If you want to change the thickness of the sheets, use only 2 sheets.

After cutting out your own work to replace the damaged base gasket, don't forget to clean off any remaining pieces of the stock gasket from the engine side. The stuck-on gasket may ride on the crankcase side or remain on the cylinder, but by scraping it off with a scraper or cutter knife and leveling it with an oil stone, the new gasket will adhere to it and prevent unnecessary oil leakage.

Also, when the cylinder head nut is tightened to the specified torque, the gasket seat may be slightly crushed due to initial familiarity. After restoring the engine and driving for a while, check for oil seepage from the gasket area and retighten the nut if necessary.

If you use overlapping sheets to match the thickness of the gasket, it may be pushed out from the gap between the crankcase and the cylinder when you tighten the nut. This tends to happen when the tightening torque is too large, but there is also the aspect that the overlapping of the sheets makes it easier for the mating surface to slide and escape outward.

For example, if the thickness of the gasket to be made is 0.8mm, there are two ways to make the gasket, one is to use the 0.3mm and 0.5mm sheets on top of each other, and the other is to use the 0.8mm sheet by itself. 0.8mm sheet by itself will reduce the risk of gasket overflow, torque loss and oil leakage.

It is a prerequisite to check in advance whether genuine parts are available for maintenance, but keep in mind that if some parts are difficult to obtain, you may be able to get by making it yourself.