Spazz’s guide to engines that say WIIIINGA-DIIIINGA!
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You know, it really pisses me off that people give 2strokes so little credit. There really isnt any better HP/Weight IC engine around! they are really works of art.
Two-stroke engines have long been promising because of better fuel economy(yes), fewer parts, less weight (about 60% of comparable 4 stroker) and a smaller engine package
So in this section i will try to pass on my knowledge of 2 strokes. PLEASE add and comment.
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I know im not right about everything here but then again 2 strokes arent a exact science infact they kinda just run on magic installed by the installer! If your 2 stroke magic wasn’t installed correctly then you engine will be weaker and more prone to failure. The way to remedy this is to remove ALL 4 BOLTS holding your head/cylinder on. I know I know its so hard! its going to take forever and all those 100’s of pieces, gee how can i put it all back together right! ok now, have the sexiest girl you can find give you ENGINES piston a kiss! DONE! reassemble and have fun!
+++OVERVIEW of 2 stroke engine+++
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OK now srsly
here is a basic HP(high performance) 2-S (2 stroke)
YUP its that simple!!! you have a carburetor in front. this is you MOST VITAL PART OF A 2-S!!!! this delivers your oil and internal engine cooling!!you see there is no oil in a 2 stroke like there is in a car. The parts are specially designed to be able to handle he horrid heat and pressures inside a 2-S. The cooling provided by the gasoline provides another benefit. It boils the fuel! this makes the fuel much more flammable then what your 4 stroker engine burns because it is 100% available to be burnt before the piston reaches bottom BEAUTIFUL!
However when you let off the throttle on your bike it loses both lube and cooling! because of this 2 strokes have a reputation for blowing up. its not the engines that are at fault though its the operator! for this reason. All you have to do is pull in your clutch. A 2 stroke engine will run more hours before failure at 100% throttle then 75% 50% or 25%. Funny huh? So never be afraid of hurting a 2stroke with stress.we dont have to deal with that. thats a 4 stroke problem!
REED VALVES:
Typical Highperformance Carburetor for what looks like a 250cc 2-S:
OK next is the reed valves. these are simple enough they go between your carburetor and your crankcase, they only let air go in one direction.the best valves are made from fiberglass(~$10 per reed). maybe carbon fiber IDK i never wanted to pay $40 for a $5 part. But the metal ones just suck for anything high performance, trust me.
OK on to the crankcase!this is where things start getting cool, your fuel ait mix get sucked into the crankcase and cools/lubes/cleans everything (yes it cleans also, because of this air filters are not all that important for 2 strokes unless you are riding in dust clouds)
Ok so now we have crankcase full of fuel steam, piston comes down, compresses the steam and then the transfer port opens and it rushes into the cyl, but wait! The piston displaces more air from the Crankcase then what can fit in the cyl! Because of the holes on the side it can only hold 1/2 that air. So all the exhaust runs out along with 1/2 your fuel air mix but it gets shoved back in by the sound pulse reflected by the expansion chamber! (exuast tube thingy) just like a giant turbocharger but even better AND CHEAPER!!!!
ok so now the piston comes up and right before it hits top KABLOOM. with all that extra pressure its a hell of a explosion and the piston starts down. Down down down untill it is just past 1/2 way down. then BAM again as the piston exposes the exuast port to the expansion chamber just as all the exuast has been sucked out by scavenging the intake port opens and in rushes cold fuel soaked air,some runs out the exhaust only to be pushed back in by magical sound waves
Most HP 2-s have LOW compression ratios (like 8.0-1) from the ports in the side of the engine, this is because, the Higher ports give the engine more time to breath when its turning 10,000-15,000 RPM There is big long equations for figuring port area*time exposed = flow but it comes down to this: higher ports = lower compression = higher RPM= Good. Lower ports = more compression = Low RPM = Bad.
a high performance 2stroke cyl with exhaust port shown (intake ports are the small ones on the side)
Some 2strokes have adjustable exuast port timing. This is a VERY cool thing for TRAIL BIKES NOT RACE BIKES it kills the peak power because of the “long” expansion chambers needed to keep the system tuned properly. Inside the exhaust port there will be a small heavy duty sliding thing on the top of the port, this will raise higher as RPM’s increase causing the port to open sooner/later then would be with a static port.They work great for creating a flater more easily used (for n00bs) powerband.
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Well i was going to get around to writing the part about the expansion chamber this is going to be like a all week affair writing this file. but since you are so impatient. Here, read up on expansion chambers
The reason MOPEDS are not efficient is because they usually dont have expansion chambers. And if they do then they would be what i call “long piped”.Mopeds are FAR FAR from high performance, babe. WHen i say high performance im talking 10,000RPM or higher whiel making 1hp per 3 cc’s or more.
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++Expansion chambers++
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“Long piped” is hat i call it when the graduation of the end of the exp chamber re not steep enough to reflect much of the sound pulse at a given RPM However if we make the pipe have steeper sides then efficiency goes sky high
“steep pipe”(but not steep enough IMO):
^^ L-4 the “diffuser” is the part of the pipe that creates a “scavenging effect” aka suction helping to bring more fuel air mix into the cyl. the steeper the angles the higher the efficiency ideally this would be like 65 degrees for L-4. but then our RPM range would only be a few hundred thousand rpm’s wide not verry wide when you are turning 14k
L-2 is the part that reflects the sound pulse back to the engine there by forcing your almost wasted fuel air mix back into the cyl just before the piston closes it off. ideally this angle would be around 85 degrees.
Also another very important thing to remember, Any air leaks where your pipe meets your cylinder will be devastating to re-compression! Unfortunately its really hard to make a old bent up pipe mate with a old bent up engine so just replace your O-rings (they are rubber!) and do the best you can :/
Im not going to talk about the other measurements YET
the exhaust sound waves dont like being puffed through anything but a cone; even worse a cone that has been dented or notched to clear a frame tube or to provide ground clearance. They can feel every change in diameter in the pipe, expanding and condensing their pressure (remember we just lit off an explosion in a enclosed space!). They are however, willing to follow even the most sudden bend in the system so this lets us scrunch them up like you see on bikes. Sonic waves may be able to feel even the most minute changes in section but they will make any turn built in the system without slowing or losing any of their energy.
Ok but most expansion chambers aren’t straight like in the pic! this is kinda a cool subject. its because the only part of the pipe that is sensitive to bends is up at the lead-in pipe (L-3) and at the entry to the diffuser(L-4). those sections gas velocity is very high, and while the wave wont care about sharp bends, those bends will have a bad effect on gas flow. Gas flow involves the movement of matter; a wave is just energy, and being without mass, is also without inertia and therefore cares nothing about sharp corners. welcome to the wonderful world of 2 strokes
the 2 stroke engine has been ignored because of emissions laws.And there for has matured verry little since the 80’s but we do have the technology to make them usable on the road. they CAN be MORE efficient then a 4stroke.
If you still dont believe me check out this page: http://microcarproject.tripod.com/ht…d_function.htm
long pipe: 
^^^those suck^^^
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++ 2 stroke carburetors, a more in depth look+++
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Motorcycle carbs are a beautiful thing.Im going to just give you the rundown on the larger jets no need to get into float settings and idle jets just yet. But basically the suction of your engine sucks fuel up into the venturi and this flow of fuel is regulated by your “Jets” they are just little bolts with highly precise holes drilled into them. Another piece regulating much of your fuel flow is your needle this needle slides in and out of your main jet as you give throttle letting more air and more mix pass the slide If you are still curious about the internal working as a carb i suggest you disassemble one and find out for yourself!
Picture showing throttle openings and the jets that are in play at a given throttle setting.
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++tuning of 2 stroke carburetors+++
RICH:
ok lets cover some bases first. When and 2 stroke is running at low RPM/throttle and it sounds sounds like “DING,dingDININding ding”(<=thats for the nubs)it is not firring everytime the engine turns. this is called "4 stroking" and is usually caused by a RICH condition (to much fuel) It can also be caused by low compression/throttle opening or poor exhaust or spark plug performance but we are talking about carbs here so lets assume its just the carb.
also when running with a heavy rich mixture at high throttle openings it will "cut out" that is, you will be full trottle and your bike will lose power suddenly but only for 1/10-1/2 of a second this is from the fuel building up in your crankcase and splashing its way up to the cylinder where it floods your sparkplug with gas causing it to not spark.
You also get more cooling and lubrication to your engine which will extend the life 2x over a slightly lean condition. It will never hurt to run a engine a bit rich the only down sides are
1. about 10% less power (im guessing)
2. Sparkplugs you will go through spark plugs faster, this can be helped by going up 1 spark plug heat range at a time(i will explain later)
3. More “spooge” (black oil shit) from your exhaust.
Most racers will run their engines lean. this created a MUCH hotter combustion and a faster explosion causing the engine to “surge” its hard to expla
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++++Fuel injection in 2 strokes++++
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Did you know that 2 strokes can be Fuel injected? They made a few prototypes of the didge neon back when. they were actually great engines/design.but It was really just an engineering venture.
“The final 1.5 liter three-cylinder would have produced 95 horsepower and 128 lb-ft (174 Nm) of torque at a low 2,400 rpm, and be about 80 pounds lighter than the 132 horsepower 2.0; it would have been more powerful overall and probably more responsive than the 1.8 and 1.6 liter engines used in many export Neons; gas mileage was estimated at 10% higher than a conventional engine of similar power. Like the new Hemi, it had two spark plugs per cylinder; it also used a supercharger.
In the end, the main problem might have been that the largest advantage of two-stroke engines was increased gas mileage, and that other technologies, applied to four-stroke engines, had much the same effect; and that customers were not generally asking for higher gas mileage at that time., Chrysler’s limited resources, customers’ priorities, Bob Eaton’s penny-pinching, and the takeover by Daimler may all have doomed the program as much as NOx emissions and regulatory issues.”-http://www.allpar.com/neon/stroke.html
WITH NO EXPANSION CHAMBERS! (expansion chambers are BIG and make loud pinging sounds is probably why)
http://microcarproject.tripod.com/html/fuel_injection.htm
^^not the dodge neon just a some info on the subject^^
Ugh im done writing for today :/
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