Most owners of old two-stroke motorcycles know that they're harder to store long-term compared with four-strokes because the engine internals are more exposed to the atmosphere. With some understanding of the engine you can with a single-cylinder turn it in the top-dead-center which will close the intake and exhaust ports.
With a two-stroke engine the crankshaft bearings are only being lubricated by the two-stroke oil in the fuel mixture when the engine is running and any moisture in the air will settle on cooler metal. A capful of oil down the bore may keep the piston and rings coated, but it won't touch those crankshaft bearings, and if there's a spot of corrosion on the faces that's about the most costly repair on any two-stroke engine.
It's not a glamorous component, but you're stuck without it. Your motorcycle's regulator-rectifier turns alternating current (AC) produced by the charging system into direct current (DC) and also controls the charge going into the battery. That's vital because enough power at idle to run the engine and any accessories, which is about 20 volt AC, jumping to 100 volt AC when revved.
Any excess current is converted into heat, which is why a regulator-rectifier needs to be mounted in an exposed position to use airflow to keep it cool – and why it's kitted out with fins, as you can see in the picture. But that means it's also exposed to dirt and moisture and the block connectors can get grimy and increase resistance and heat.
If your motorcycle is a few years old it's worth checking the condition of those connectors as 80 percent of the time it's increased resistance there that starts to stress the regulator-rectifier itself. Cleaning them, then sealing them with non-water-based grease is good preventative maintenance.
Most times when your motorcycle is having problems or has quit running, the problem is traced back to a poor electrical connection. It takes time to trace where that problem is located and could have easily been fixed. Over the years I have seen all kinds of wires connected together using wire nuts and just twisted together with black tape wrapped around them. Many use crimp connector which works fine, but over time the wire can oxidize which will fail in time. Especially in a tropical climate like Thailand…
The soldering method, if done correctly, will be a permanent connection. It is not that hard to do, if you follow these steps for proper joining and soldering.
The tools and supplies needed, are easily found and cost little:
Thankfully it's rare that anyone has to pull an engine apart after some catastrophic issue these days. Modern motorcycle engines are generally reliable and hardly ever give major trouble. Routine maintenance and replacing ancillaries should be all that is needed, with valve clearances usually the only time we have to delve inside.
But occasionally something breaks, or hits something else, or wears out and the first we know is a nasty noise, loss of power, a bad smell or – worse – the rear locking up and bits escaping. When this happens, what is the best course of action?
The first step is simple. Diagnosis: see what went wrong and work out if it's something you can repair. If you can peek inside the engine through a hole made where a part escaped, then the whole engine is very likely ruined. Otherwise, does it turn over on the starter? Will it select neutral and change gear if you move the rear wheel? Is there oil and water? It so, is there metal swarf in the oil? Could it be chain, brakes or gearbox? All these questions will help isolate the problem, so that you can then decide if it's economical to fix or replace.
Production lines have all necessary controls and inspections engineered into them, but an individual building an engine must take responsibility for fits and tolerances. This is the case in a race shop or for a home builder. The basics are in the available manuals for all to see, and you begin, as one man put it, ‘By just getting into it.’ We all begin with just the desire to do it and w willingness to learn from mistakes. Experience causes the unfamiliar to become familiar.
I got a call from two club racers who’d decided to change the crank in their Yamaha, Honda or a Kawasaki. They basically wanted someone to tell them they could do it. They had the manual, some tools, a new crank, and desire. It took them weeks of evenings, and we spoke on the phone often. They found and removed fasteners, pulled the heads and cylinders, and then the pistons.
The parts began to look less scary and more familiar to them. Engine features began to make sense. Each step was in the manual – pulling the ignition rotor and crank primary primary gear. Storing, even labeling, the parts as they came off. They gradually became their own experts.
Gearbox problems are very rare nowadays, but normally only affect first-to-second upshift. The reason for this is that gearbox ratios are not evenly spaced but are widest apart at the bottom and become closer at the top. As a result, the speed difference and the shift impact are greatest on the first-to-second upshift.
That's why quick shifters normally work better from third upwards. This engagement impact from first to second gear is also transmitted through the gear teeth and then through the gear itself to the shaft. You can imagine what forces act on these gears when you are playing rough with 200 horsepower at the rear wheel. To make the gearboxes last and survive the high tooth-to-tooth pressure, gear surfaces are hardened by a nitride coating.
All of us who work on motorcycles, we have all been there; the painter or powder-coater forget to mask a thread. Taps and dies are good on small threads but what about larger ones? What if you're already fitted key parts and access is limited? Fill the back of any holes or spaces with clean rag and add masking tape if necessary.
Apply paint stripper (even the modern weak stuff) cautiously with an artist's brush then walk away for 30 minutes. Carefully dig into the threads with a pick, old tooth brush or similar to loosen the finish and vacuum off everything that loosens.
Almost all suspension feels good on smooth surfaces, but only some carries on feeling good over bumps.
Designing damper pistons that flow fluid inside forks and shocks, and the shim stacks to control them, takes time and money. It also costs money to keep internal friction at bay. That's why a set of Ohlins superbike forks will cost so much more than OEM replacement. You're paying for the precision of the machining, the accuracy of the damper cartridge bore, and trick coatings on moving parts. That matters if you're trying to outbrake Valentino Rossi…
But sometimes you wonder if suspension feel is also about company philosophy. For many years in the '90s and early 2000s a good amount of motorcycle manufacturers, just didn't appear to think good high-speed control was particularly important. And maybe for some customers it isn't.
Front forks contain oil which creates damping. You can change the characteristics of the fork by changing the height of the oil inside. If you increase the oil height, then the fork will become slightly stiffer and more progressive. If you lower the height, then the fork becomes less progressive. All front forks have manufacturer's specifications when it comes to oil heights but we will try to tell how to adjust the height easily on a general front fork.
Firstly, you will need to remove the fork from the motorcycle. On some forks, it is possible to adjust the oil height with the fork still on the motorcycle but, for the most accurate measurement, remove it from the motorcycle.
Undo the top fork cap and slide the outer fork tube down so you can reach the spring. Take a spanner, place it between the coils and hold the locknut on the damper rod.
Some specialized tools are needed if you really want to check all the engine component specifications.
Before we can cut the valve seats, the head needs to be cleaned, degreased and carbon deposits removed. The header pipe gasket will be pushed into the head and locked in with carbon. You might need a pick or similar to dislodge it. They are usually made of copper and are one-use only since they compress to make a good seal. A new gasket should be in the top-end rebuild gasket kit.
When the header pipe was removed the nut locked onto the stud, causing it to wind out of the head. Now is a good time to fix it back in place. Use high-strength Loctite as the low or medium type is broken down too easily with heat. Wind on two nuts to the stud and lock them together. This will allow you to tighten the stud into the head. Two spanners are then used to unlock the nuts so they can be removed from the stud.