(1)- TWO STROKE PISTONOLOGY = TUTORIAL 

Oh boy! #1- the pins keep the rings in place on 2 strokes to keep the ring ends from snagging the ports. #2- the arrow on the piston is to indicate the front of the piston so the ring pin is in the proper location and to be sure the wrist pin bore offset is located on the proper side of the bore, not because the piston is thicker on the side with the arrow, even 4 strokes use the arrow but no ring pins.

The rings will hardly move at all when they are compressed into the cylinder, the pins are to make sure the open ends of the ring(s) do not rotate into the port openings. Only 4 strokes can allow the rings to rotate as there are no cylinder ports. The explosion does not go past the ring to force the other ring out! Two rings simply provide more sealing than one and they are offset so any gases getting past the first one's locating pin won't go through the next.

ok lets clear a few things up, with no offence meant to anyone, including the op, the arrow is on oem (original equipment manufacturer) pistons mainly, and always faces the exhaust port, the size also is on the top, and again mainly on oem stuff, and some high quality after market producers, that I am not here to promote, the rings only move round to be free in the slot to expand where they must stay located, in a line with the locating pins that also act as a barrier from the expansion of gases, no explosion should flow below the top ring, not all 2 stroke pistons have 2 rings, most high performance motocross or racing bikes have one, and require a lot more maintenance, as in ring changes and little end bearing changes after a few races, not all two strokes have cast iron barrels, not since the dark ages of the 1960`s anyway, and some two strokes employ a flat top to pistons for reasons you need to research, as I do not have all night,

the two stroke engine with the better lubrication (like the 4-stroke) and no loss of fuel in the exhaust is called piston charger engine

You cured my insomnia. Thank you so much!

Says that rings don’t push outward on the cylinder “Let me prove it to you” /proves that rings push out on the cylinder

You should know that there is no such thing as an explosion in an engine...

They stop the rider from being killed from the explosion igniting the oil. peace.

Not all pistons have two rings, I have a ECHO PB265LN and it has 1 ring for a two stroke.

load of bollox 111

what if you only get one spring ring? do i put it on th etop or bottom?

well it's a litle more complicated,and wenn i see the piston you got on this vedeo all are just junk,to understand 2stroke you MAY study the gase flow from the air (box or chamber) filter allaway true the deep end off your expemded exhaust pipe,also at low rpm the port of ce cylinder or at high rpm should note be the same design that's,for example why yamaha use ypvs valve

interesting video... more interested in how much drugs / drinking you did in the 1980's to sound that frayed around the edges?

An explosion does not cause the piston to go down. It’s a controlled burn. The expansion of nitrogen gas left over from the controlled burn is compressed by the piston thus pushing the piston back down.

hi.great videos.i have a honda dio sk50-m 1999 50cc and want to replace with 80cc piston.do i need to change the rod to or not.sory for my poor english

Sorry but 2 strokes can also only have one pistol ring I work on old bikes and back in them days they only use one ring

Only from America could come the word Pistonology,what the hell is wrong with you yanks??.The rings expand onto the bore under compression before ignition as well as ignition and the pressure between the two is small.Pistons have to be oval, as the gudgeon pin mass in the piston is greater than the front and rear wall and would expand at a greater rate and seizure would be inevitable even with low expansion alloys that the Japanese bought into motor cycle specifications in the early sixties.

Stupid...Rings do seal because of their tension! ALWAYS! You just happen to have an inflatable ring design. Kinda rare since the 90s I think!

@eFzjcb121 Look at the rings, if you put them on top of each other one will be larger in diameter on the inside, that one gets the wavy expander and they go on the bottom ring groove.

YOU are one DUMB, YA-HOO... BET YOU DONT KNOW WHAT THAT IS , MATE..

I bought a set of rings for my Yamaha yt125 one ring has 1t 25 and the other has 2t 25 on it which one goes on the top groove and which one goes on the bottom groove

If I want to install piston rings, is there any difference between upper and lower ring ?

fyi..There's not always a pin in pistons....Older 2 strokes didn't have them..

Hey I'm doing a top end on my 88 yz80, the cylinder walls are in good condition and still have a cross hatch pattern on them, but I have low compression and just replaced the ring (one ring piston). The piston has blowby and the ring was installed properly, this just means time for a new piston and ring right? No replating or boring necessary?

piston ring groove, i.e. the action of the gas pressure increases the sealing capability of the piston ring.

look its 2 stroke they are made that way and made well.

the arrow is pointing at the exhaust port... yea ... but it is primarily calculated in weight for the bang and compression (up and down)

what if you only get one spring ring? do i put it on th etop or bottom?

need help. any idea at the front of my piston at the top keeps chipping off on yz125 i change the piston and it happened twice now

And watch your eyes when taking those freaking things off...

What does it mean if I just blew my top end and when taking off old piston I seen there was literally no black carbon residue at all and chunks of piston broke off?

@eFzjcb121 i believe the bottom if only one

what if I only have 1 piston ring on my 2 stroke

thats why 2 strokes are so damn a fast

This guy "kind of" knows what he's talking about, but he misses a few points. One - he forgot to mention that the little arrow on the top of the piston "always" tells you that that side of the piston faces the exhaust port. Two ~ what caused the piston in his hand to fail is that the ring keeper fell out (that keeps the ring from spinning over time), the ring did not break. Finally, ring "spring tension" holds the ring against the cylinder wall, when the fuel charge explodes it does get behind the ring and push it against the cylinder wall. If the ring is worn or loses tension that's when the charge blows by.

Is this a 100 125

Gas port pistons place pressure in the ring land .

some 125s have 1 ring

@terence20001 Yes sir!

why the hell does a 2 stroke need a oil seal ring lol

I always lateral port my pistons it helps inflate the rings on the compression stroke very noticeable on the rolling road

there is when they go wrong! :-)

Well done, sir.

bad to listen you speech

my position and head has a lot of seize marks on one side what does this mean

great vidio :)

👍👍👍

Very interesting,nice tutorial.

"pistons are complex, simple and have few rules"...... Okay!.... to translate, pistons are indeed simple but not complex! they cant be both! they may do complex things and have complex constructions but in reality their job is simple, to transmit the linear force of expanding gasses via the connecting rod to the crank to produce rotation whilst pressurize the fresh charge below it as well as releasing it into the cylinder, But the piston itself is a simple device for transmitting force!

the ring gaps on a 2 stroke must face towards the inlet

Wow!! I'm sorry but I think you may want to go back and study more. A lot more. Some of the info is correct like the markings on the rings go up and there are arrows on the pistons to reflect how it needs to be installed. The rings really don't move on a 2-stroke motor. Yes they need to "move freely" but that is so they don't get stuck to the piston and develop a carbon issue. Many of the things you are talking about in your video is for 4-stroke motors. Yes get a ring expander. They are cheap. (under $20) and get a ring compressor to install the piston. Pistons are basically round. Take a quality micrometer and measure a few different new ones. Rings in the piston things? You mean against the ring pin in the piston? If you are going to talk about pistons use all the correct terminology. Search for korihandbook on Federal Mogul's website for everything you ever wanted to know about rings. korihandbook.federalmogul.com/en/ As other Arno Low mentioned below (It's no rocket science ... it's already broke how much worse can you make it?) I recently purchased a non running rusted up 99ci 4 cylinder 2-stroke motor. It was broke how much worse could I make it? Well I made it whole again. It needed a lot of work and a full complement of parts. For instance every one of the $102 2-stroke pistons had a spec pamphlet included. I wouldn't have thrown over $400 in pistons into a block that just had nearly $500 in machining without knowing what is what first. This motor now spins these new pistons 6300 RPM making well over 140HP for as long as I can keep the gas tank full. Each and every 2-stroke I have had apart has been a slight bit different but they all follow the above rules. When those rings spin freely your motor will go boom in short order. This particular motor had broken 4 of the 8 rings. It still made 115PSI static compression on all but one cylinder and that low one was just a hair under 100 PSI. The low cylinder had a completely missing top ring and was only using the low ring to seal with. Others had parts of or cracked in half rings. Oh and if your example of how they work under operation (with explosions providing the sealing pressure) then how can I get 127 psi of compression pressure on a static compression test? The rings seal under their spring tension provided the end gap is correct and the ring is installed right side up. If you want to summarize what a piston ring does in all motors it is this: Rings seal the combustion chamber and they provide the only path for which the heat from the piston is transferred into the cylinders. In two-stroke motors the rings must have a measured bit of play in the ring groove in/out & up/down but not rotationally. If they rotate the ring edges will catch on the exhaust or intake ports and break. My Yamaha twin cylinder sled motor did this and destroyed one cylinder. The Evinride V4 above did it and destroyed 3 of 4 pistons, a head and 2 of the 4 cylinders.