What to Do When Dismantling a Rusty Engine?

I've been asked, why are you trying to fix a motorcycle that's so shabby? I've had people ask me what I like to do with my motorcycles, but if you don't like old motorcycles, you won't understand, and if you think I'm a bit weird, I can't help it. For the past 10 years or so, I've been tinkering with, fixing up, and sometimes fully restoring old motorcycles that could justifiably be called "battered". Here you can see some of the techniques and ideas I've used to remove cylinders that were too rusty to pull out easily.

An unavoidable road for old motorcycle lovers!

I think it's natural for each person to have different sensitivities, such as "I'm personally interested in it" or "Even if I wasn't interested when I first encountered it, there's something about it that strikes me ......". In my case, I was interested in the models around the year of my birth, and I was blessed with the opportunity to repair or fully restore them (?). It was a great opportunity for me. I also dared to work on it as training for myself, or as a study to accumulate restoration experience. This model is the first generation of the Super Cub, the C100 series with the OHV engine, a late model of the early series just after its release, produced in late 1960. The very early series (1958 to early 1960), just after the birth of the Super Cub C100, was commonly known as the "Hanging Cub" because the cylinder was mounted suspended from the frame pipe.

It is important to make a commitment a few days before disassembly!

Once you have scheduled the disassembly of either the engine or the chassis, spray the loosening threads of the bolts and nuts with an anti-corrosive penetrating oil spray and leave it on for several days before the work. This is essential for disassembling a normal model, but even more so for a battered, rusty engine. This is because loosening the bolts suddenly will cause galling and the bolts will often break. In fact, the most difficult part of the restoration process is the removal of the bolts and nuts.

As you can see, the clutch housing and primary driven gears of the late 1960 production model are much lighter than those of later mass-production models. The early 1959 and earlier production models are even more distinctive. The crankcase was a "sand type crankcase".

Is condensation in the fuel tank the cause?

Relatively good degree because it was not completely open-air storage. It was a Super Cub C100, but the water that accumulated in the gasoline tank traveled down the fuel hose to the carburetor, and then entered the engine through the open intake valve. As you can see, the inside of the cast iron cylinder was rusted to a crisp. Disassembly becomes extremely troublesome in this situation.

Cylinder removal is one example.

The cylinder and piston rings are completely rusted. The cylinder and piston rings are so rusted that it is not easy to remove them even if you hit the cylinder and piston rings with a hammer. In this case, I wanted to restore the engine to its original condition, so I disassembled the engine carefully not to break the cylinder and not to bend the connecting rod (not to reuse the piston). Here I used special tools called bearing and gear puller.

Anti-corrosion penetrating spray and heat fusion

The gear puller I had was a perfect size, and I was able to hook it up to the cylinder of the cast-iron block and push the piston in through the socket wrench frame. Even when I set the puller and tightened it up, it didn't budge at all. After a week of no visible change, I took the engine outdoors and heated the cast iron cylinder with a handy gas burner. I then tightened up the puller and the cylinder lifted just a few millimeters!

A cylinder that fell out after 2 weeks of work

The cylinder was lifted slightly (by a few millimeters) by using the power of heat in the first week, and after that, I roasted it with the burner every day, tightened up the puller, and kept spraying the cylinder with anti-corrosion penetrating spray while applying tension. I kept spraying anti-corrosion penetrating spray while prodding. A week after I started this strategy of using heat together, I tightened up the puller and the cylinder lifted up by a cheat! So I tightened up the puller all at once.

Restoration base so good that there are no missing parts.

The Honda SL70K0 was produced in 1971 as an export model exclusively for the USA, and was the original Honda horizontal 70cc engine model with a return 4-speed transmission. This was followed by the SL70K1/K2, and then the XL70K0/K1 (both with horizontal 70cc engines). If a modern version of this series were to be produced, it would undoubtedly be a very popular model. The full restoration was completed at a leisurely pace. The motorcycle is currently being ridden by a fellow motorcyclist in excellent condition.

After returning home, I enjoyed the full restoration of the work at night in the garage. It is a very blessed environment to have a garage where you can enjoy tinkering with your motorcycle day and night, regardless of the weather. Owning a garage was a priority for me before buying a house.

The energy to make such a raggedy motorcycle beautiful!

The foreground in the top photo is the before, and the bottom photo is the after when the assembly is complete. Isn't it fun to see the difference? The vehicle is a Yamaha YA5 Deluxe that was released in 1962. I met the motorcycle in the photo above at a parts exchange event, and despite my worries, I was able to get contact information from the vendor, and a few days later, I decided to buy it and pick it up. I decided to fully restore the motorcycle because it had a solid frame structure. This was the first Yamaha air-cooled 2-stroke mixed gasoline era motorcycle, and it was also the first Yamaha model to use the rotary disc valve. During this full restoration, I was able to learn a lot of things and restoration techniques.

What I didn't expect was the surprisingly large number of "new parts" that were available. There are not many fans of this model, and when various parts were listed on the internet auction, I could win the bid at the approximate listing price without facing any rivals. The full restoration work itself was able to be completed in almost a few months. The whitewall tires, which are the key point of the design, were purchased by mail order from a shop in Bangkok, Thailand, where Japanese old motorcycles are currently in fashion. Thailand, a pro-Japanese country, has been importing Japanese motorcycles (new and used) since the 60s, and because of this history, the country is currently experiencing a classic motorcycle boom. Because of this history, Thailand is currently experiencing a classic motorcycle boom. The fully restored Yamaha YA5 Deluxe took a whole year to get the engine going. You can see how to avoid this problem by reading the previous articles in the maintenance section of Webike Magazine. If you are a fan of old 2-stroke motorcycles, you should be especially aware of these cases.

During routine maintenance, bolts and nuts that are supposed to loosen do not loosen. Why can't I use the right tools? There must be many Sunday mechanics who have had this experience. It's not uncommon for bolts and nuts that should be easy to remove to not work as they should. It's no good breaking a bolt or threading a nut in a hurry. Even if only one bolt is not loose, it is not possible to carry out maintenance, replace parts, or proceed. In addition, the disassembly of the parts of a battered old motorcycle is not an easy task if the bolts and nuts are not loose everywhere.

What we are trying to do here is to disassemble a Honda Super Cub C100 engine that was not seized, but stuck with rust. I bought this early production series C100 with the intention of doing a full restoration, but it was in a much worse condition than I had imagined. As for the body of the motorcycle, we sprayed a lot of anti-corrosion penetration spray including bolts and small screws a few days before the disassembly work. By spraying with the anti-corrosion spray, we were able to loosen and remove all the bolts relatively easily during this work.

In this way, the bolts and nuts are thoroughly sprayed with anti-corrosion penetrating spray a few days before the disassembly schedule begins, and torquing is carried out in advance. At that time, if there is a bolt or nut that will not loosen, apply heat to the bolt with an ignition burner or heat gun, and then apply heat to the surrounding area as well, and then spray the anti-corrosion penetrating spray directly onto the threads through the gap between the bolt and nut. This arrangement is one of the know-hows that we would like you to know.

Also, the more tools you use for disassembly work, the more you want to use products that are solid and reliable. Use a socket wrench or a spectacle wrench, not a quality tool like an automotive tool. If you feel that you need to loosen a bolt or nut, be sure to have a special socket (such as a tornado socket) that can be used for that type of work. Electric screwdrivers and impact wrenches that can loosen bolts and nuts at once with high torque are also good for disassembly work. We hope you will try them.

The most difficult part of disassembling the Super Cub this time was, as mentioned above, removing the cylinder. The cast-iron block cylinder body and cast iron piston rings were tightly adhered to and almost as one. By chance, I was able to use my gear puller, but it is very difficult to disassemble a multi-engine like this. If I had noticed that the rust adhesion between the cylinder and piston was so bad, I would have sprayed a lot of anti-corrosion penetrating spray through the spark plug hole and burned the cylinder from the outside with a handy burner before disassembling. I hope you know that this kind of "setup work" is very important when disassembling.