See full version: Sludge out of a 2 stroke exhaust
There is only one draw back to all this and that is that this supercharging only happens at the specific RPM that the pipe was designed for. Running the engine at any RPM above or below the designed RPM and the supercharging effect will be much less effective. That is why two strokes have such a narrow power band. here
One problem with two stroke exhausts is that they can get plugged up with carbon from the oil used to lubricate the engine. The bike will start easily but just will not rev up. This is especially true of quite exhausts. If the exhaust has removable baffles or is fiberglass packed, you can easily clean them and replace the fiberglass packing. If the baffles are not removable it is much harder to clean them. Many stock two stroke exhausts have non removable baffles or have only one or two baffles that are removable. The different baffles collect the unburned carbon and plug up but you can't easily get to them. There are several cures. Non of which are easy or cheap. [links]
Two strokes are all about the exhaust. When combustion occurs in a two stroke, the piston is pushed down by the expanding gases uncovering the exhaust port. The exhaust gas rushes out into the header pipe and a pressure wave is created. This wave can be either positive or negative in pressure. If it is a positive wave and hits a change in diameter in the tubing of the exhaust pipe it changes to a negative wave. Hit another change in diameter and the wave changes back to positive. This wave pressure can be as high as seven pounds per square inch (Both positive and negative waves) and travels at 1600 to 1700 feet per second.
If the pipe is made just right, a wave with negative pressure reaches the exhaust port just as it is fully open. This sucks the exhaust AND part of the new intake charge into the exhaust pipe. Then, just before the piston closes the exhaust port, this negative wave changes to a positive wave and pushes the fresh intake fuel charge BACK into the cylinder. All this happens in three to four thousands of a second. This sort of supercharges the engine, giving the high power out put of a two stroke engine. Without that properly designed exhaust pipe called an "Expansion Chamber", the two stroke engine will have no real power. here
¶ Walter Kaaden, the chief engineer for MZ motorcycles in the 1950s, is generally considered the father of the modern two stroke expansion chamber. He reportedly said "You'll know when you have the design right, because the chamber will then be impossible to fit on the motorcycle without having it drag the ground, burn the rider's leg, or force the relocation of one or more major components." more
Detergent cleaning
This method is effective with more modern oil residues and works well in conjunction with the solvent method. Bikes run on fully synthetic oil in theory shouldn’t be too bad in terms of exhaust debris but unless given the berries and allowed to breathe deeply that ultra-expensive but partially combusted two-stroke oil can cause problems. Similarly many 1980s restricted slo-peds never really got a chance to rev at full bore and their exhaust systems are often clogged with oily sludge. With the exhaust plugged with anything that can withstand a bit of heat add a brew of piping hot water and detergent. Experience has shown that pine based industrial detergents used for floors seem to be the best.
Post cleaning I’ve always left the baffles naked and have suffered no problems but you might want to check with owners of similar machines just to ensure there are no issues with your particular machine. If you do choose to re-wrap the baffle, fibrous loft insulation material makes a very useful alternative to the factory stuff but you can purchase specific wadding (many motocross dealers stock this).
How you clean baffles depends on the type of oil contamination. However, the time honoured method of a wire brush and a gas torch are still valid providing you take the obvious precautions. Once coated in oil and soot this material makes an impenetrable barrier to exhaust gases and cannot be cleaned. Removing the wadding gives access to the all important passages. [links]
Please note, if your exhaust is painted matt black, prolonged contact with brake fluid may cause staining or paint damage (chrome systems are unaffected).
Caustic soda needs to be treated with care as it will burn the skin and eyes. Safety glasses and disposable gloves are the minimum level of protection; a face-shield and strong rubber gloves are the preferred option. Dissolve the caustic by adding it to lukewarm water. NEVER add water to caustic as it will become incredibly hot and possibly effervesce. A 10 percent solution is generally sufficient for most applications. Caustic is available from hardware stores and commonly used to remove fat and grease deposits from pipes and drains; a use not too far away from our own.
This strong alkali reacted with the acid components of the partially burnt oil forming a soap allowing the sticky carbon from the silencer and baffle surfaces to be washed off.
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The PVC valve allows the ventilation of controlled amounts of internal engine gases into the combustion chambers, allowing them to be burned. When it becomes clogged, it can cause the engine to become internally pressurized, forcing oil past important seals and into the exhaust stream. This can be accompanied by bluish smoke, reduced fuel economy and oil-fouled spark plugs. You can easily address this problem with a simple replacement of the valve.
Valve guides are an internal part of the engine that help to control the flow of gases into and out of the engine. They are lubricated by engine oil and have seals around their shafts that can become worn, allowing engine oil to seep past them. When this happens, engine oil leaks past the worn valve and into the flow of exhaust gases from the engine, accumulating in the exhaust pipe. Usually, this problem will be accompanied by bluish smoke coming from the exhaust.
Pistons are the part of the engine that harnesses the energy from fuel combustion. Ignition of the fuel mixture forces them up and down in their bores, providing energy to move the vehicle. They are sealed in their bores by piston rings around their circumference, which are lubricated by engine oil. When these rings become worn, oil and fuel can leak past them into the exhaust system. This problem will be accompanied by white to bluish smoke and a noticeable loss of engine power. [links]
If anything besides exhaust is coming out of your vehicle's exhaust pipe, it could be signs of trouble. In the case of oil in your exhaust, it is important that you address the problem immediately. Keep in mind that almost any sign of oils exiting from the exhaust system will require professional evaluation.
This strong alkali reacted with the acid components of the partially burnt oil forming a soap allowing the sticky carbon from the silencer and baffle surfaces to be washed off.
Caustic soda needs to be treated with care as it will burn the skin and eyes. Safety glasses and disposable gloves are the minimum level of protection; a face-shield and strong rubber gloves are the preferred option. Dissolve the caustic by adding it to lukewarm water. NEVER add water to caustic as it will become incredibly hot and possibly effervesce. A 10 percent solution is generally sufficient for most applications. Caustic is available from hardware stores and commonly used to remove fat and grease deposits from pipes and drains; a use not too far away from our own. here
This method still works well for older type two-stroke oil deposits but is of limited use if your bike has been run exclusively on modern synthetic oil. The corollary of this is that modern oil shouldn’t coke up silencers anyway and therefore there’d be little carbon to remove.