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Wikipedia describes four-stroking as: Four-stroking is an undesirable operating condition of two-stroke engines, where they instead begin to fire every four strokes, rather than every two strokes. This firing is uneven, noisy and may even damage the engine if allowed to continue unabated. Four-stroking was often a cause of poor idling in two ...


20

Briefly: The exhaust pipes are shaped to suck gasses out of the combustion chamber over a range of RPMs. Somewhat longer: Imagine a 2 stroke engine without an exhaust*1. When the exhaust valve opens, burned gasses leave the cylinder. Leave the valve open for a long enough time and the cylinder will be at ambient air pressure. Now run the engine at a ...


20

There is this nice animation of a 2-stroke engine with an expansion chamber Source It works like this: While moving downwards after ignition, the piston exposes the exhaust opening, and the burned gas streams into the exhaust pipe like a (high pressure) shock wave. Due to the inertia, this gas will create a slight vacuum wave behind it, which helps to ...


13

The only two stroke diesel i'm aware of is the Detroit diesel. The Detroit diesel does use forced induction but not in the way that you think. From your description it sounds like your describing a two stroke gasoline engine. The engine draws in air into the crank case. Then compresses it and shoots it into the combustion chamber. This setup works well with ...


12

An air screw on a Keihin PWL26 only effects the idle circuit of the carburetor. The idle circuit pulls through the pilot jet exclusively. The pilot jet typically can deliver no more than 15% of the overall fuel when the throttle is wide open. The claim of 15% is based upon the inside diameter of the pilot jet and the inside diameter of the main jet. The air ...


10

Just so we're on the same page as to how two strokes work, here's a pic. I had to look it up because I had the wrong picture in my head. In looking at how the cycle actually works, the power stroke goes off creating the combustion products and power. As the downstroke begins the pressure in the cylinder is high allowing the exhaust gases to escape and ...


10

Water in the cylinder usually means water in the crankcase on a two stroke Pulling water out of the cylinder doesn't mean you pulled out all the water. Two stroke engines use ports on the side of the cylinder rather than valves at the top of a cylinder (4-Stroke). The ports run down the outside of the cylinder wall into the crankcase which means there is ...


9

Gasoline sitting for two years in the float bowl of a carburetor will surely lead to some varnish. The hydrocarbons evaporate from the fuel and oxygen acts as an oxidation catalyst changing the remaining components into other compounds leaving varnish in their wake. Varnish will coat and clog the inside of the carburetor. Float bowl, floats, needle and ...


9

My best bet is that the spark plug is too long in the first place. I don't know what the stock spark plug should be for your bike, but the NGK you are showing may/may not be completely within spec and therefor is extending down into the cylinder longer than the spark plug should. If the bottom end was worn out enough to allow the piston to travel that far up ...


9

I am not sure where you get the idea they haven't built larger displacement two stroke engines. Detroit Diesel built the 71 series which was very large displacement two stroke engines. From Wikipedia: The Detroit Diesel Series 71 is a two-stroke diesel engine series, available in both inline and V configurations, with the inline models including one, two, ...


9

Depends. A key point of 2-cycle engines is that a thing called scavenging happens with the piston at the bottom: at the end of the power cycle/ beginning of the compression cycle. During scavenging, the stale exhaust air is pushed out by fresh air being pushed in. Something is doing the pushing. This accomplishes the purpose of the 4-cycle engine's ...


8

The efficiency of any internal combustion engine is directly related to its Carnot efficiency, where efficiency equals the inlet air temperature minus the exhaust temperature divided by the inlet temperature. This is directly influenced by the expansion ratio of the gases. A diesel engine has an expansion ratio approaching 30:1 whereas a gasoline engine ...


7

You can run that fuel. I've run a 100 hours of aviation fuel through plus another 200 hours of race fuel that tends to destroy FI fuel pumps in various years of RM. I have a friend that is currently campaigning one in a vintage class race series. It's a 1978 RM250. It's fine. Two years since the last rebuilt. But you don't have a fuel pump so you don't ...


7

I know this thread is a bit old, but Detroit Diesel and GM EMD (Electro-Motive Division) have many 2 stroke Diesels. The crankcases! Well they aren't pressurized. How it works is different to a smaller 2 stroke engine. Instead of the underside of the piston 'pushing' an air fuel charge up a transfer port, these engines have an air gallery around the ...


7

I'm not a watercraft Mikuni guy, but I've dealt with a few two-stroke carbs that work in this manner. There's a few possibilities: The internal filter screen is clogged, but I'm discounting this as it's just rebuilt, and I doubt that would cause the primer bulb effect anyway. The fuel return is dirty or blocked. Verify with it running (after an ether ...


6

Perhaps you were thinking of 2-stroke gasoline engines when asking the question. Evinrude built a 3.6 liter gasoline 2-stroke for outboard boat motors. http://www.roadandtrack.com/car-culture/videos/a7300/video-insane-evinrude-johnson-two-stroke-v8-startup/ Interestingly the exhausts are in the V in this design, which is necessary as the carburetors ...


6

BSFC is just engineer-speak for how much fuel is consumed by the engine per unit of energy output¹. This webpage provides a very concise comparison for several different engines: +------------------------------------------+----------+----------------+-----------+ | Engine | @ 1K RPM | @ Peak Torque | @ Peak HP | +---------...


6

Lubrication and cooling of two-stroke engines have always been the limiting factors. The bigger the engine, the bigger the problems. A big two-stroke will have a very short service life, even with constant maintenance. Two-stroke engines burn oil in their fuel and burning oil causes pollution. The charging of the cylinders by its port arrangements mean ...


6

Renault are developing a small 2 stroke diesel with turbo and supercharger. It's name is the Renault 'Powerful' see for example - http://www.enginebuildermag.com/2014/12/renault-unveils-two-storke-twincharged-diesel-two-cylinder/


6

Water in the cylinder? The engine is in bad shape from improper storage. Even if you get it freed up there will be rust on the cylinder walls and piston rings, which will cause more damage if you manage to get it running or spinning over with the starter. The best solution is removal and complete disassembly and inspection of the engine. Make a decision to ...


6

For Two Stroke engine: One working stroke in each cylinder per revolution of crankshaft. Light in weight. Moving parts are few. Mechanical efficiency is more. Thermal efficiency is less because a part of air fuel mixture gas as waste with the exhaust gas. Noise is more. Wear and tear is more due to the smaller size of the same power. Construction is simple ...


5

Either it's in there or it isn't. If you've taken the head off, you should see the top of the piston and know if it is there or not. You don't want to refire the thing without knowing if it is there or not. If it is in the cylinder it could rub on the side of the cylinder wall and cause damage. Scoring of the wall and damage to the piston are the two big ...


5

Two stroke engines, by their very nature, require some of the 'plumbing' you note in your question. Specifically the expansion chamber. Unlike 4-stroke engines, two-stroke engines require the expansion chamber and stinger (reduced diameter over distance) at the end of pipe. The energy in the exhaust wave expands and wave front slows in the expansion ...


5

Most small(ish) diesel engines in cars, diggers, generators etc are 4-stroke. The main reason being efficiency - Although a 2-stroke engine is technically capable of more power output, a 4-stroke engine uses less fuel to produce the same power output. Many VERY large diesel engines (EG Super-Tankers) are 2-stroke, This is because they are direct ...


5

I can't recommend it. I was told that 100LL has about 4x the lead that the old regular leaded fuel had. Even on aircraft (which run at or near 75%+ power continuously) lead fouling of plugs is a major issue with frequent cleanings required.


5

Yes, you can bend the tab The metering diaphragm enriches the entire range on every circuit. If the fuel level is higher it will require less vacuum under Venturi's Law to pull the fuel from the 'float'. You can use the metering diaphragm float tab as a method to enrich all of the circuits and then adjust your low speed circuit with the fuel screw to lean ...


5

You cannot assume just because it starts it has good compression. It can have minimal compression and still start and run just fine. That minimal compression is going to be different for every engine, so you'd have to look up the specifications for the exact engine you're looking at. The deal with it is, the more compression the better it will run (make more ...


4

You can, but you'll significantly reduce the life of your engine. That's the short and to the point answer. I don't know too much about bikes, but if this were a car, I'd at the very least have someone tweak the carbs and adjust the timing somewhat.


4

It depends on where the engine is seizing Since your scooter/motorcycle is a two stroke, if you are seizing due to a lack of oil in the gas at the crankshaft you are in big trouble. More than likely this is not the case. It is known to happen on rare occasions though. The main bearings of the crank basically begin to disintegrate due to oil starvation. ...


4

I have to both agree and disagree with your statements in the question and the article. The higher fuel consumption of a two stroke engine is mostly due to the fact that it has a power stroke per revolution of the crankshaft. I however have to disagree with the article stating that the fuel delivery plays a major role in fuel efficiency of older 2-Stroke ...


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