Single Ring VS Double Ring 2 Stroke Piston? Better or Worse? 10 REASONS WHY!
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All 3 pistons you have on the table were subjected to prolonged DETONATION.
Detonation is caused by a combination of .......
1) too much HEAT, ( Cooling System clogged, or not enough air flow through the Radiators.
2) too much PRESSURE, (Compression Ratio),
3) too much Squish-Band / Quench Clearance,
excessive Piston to Head clearance will PROMOTE DETONATION,
tight Piston to Head clearance REDUCES DETONATION, (and increases power slightly, even with identical Compression Ratios).
The factories are sloppy with the Quench Clearance to reduce the need for precision in a mass produced, assembly line product.
Piston to Bore clearances, and Piston to Head clearances ARE ABSOLUTELY CRITICAL.
4) Inadequate Octane Rating of the Fuel, relative to all of the above factors.
5) Sharp Corners on ANYWHERE inside the Combustion Chamber can promote DETONATION.
This includes Platinum, or Iridium tipped, or "Fine Wire" style Spark Plugs, DO NOT USE THEM IN ANY HIGH OUTPUT ENGINE.
You want a "standard" "Copper-Core" Spark Plug which carries away HEAT very efficiently, and will never create "Hot-Spots".
Going one or two Heat-Ranges COOLER on the Spark Plug Heat Range Rating,
is good insurance against Spark Plug induced DETONATION,
but it means you will have to replace it more often because of possible increased fouling of the ceramic insulator.
The ONLY advantage of really expensive trick plugs is that they may last longer, THAT'S IT, ZERO other advantages.
ALL SPARK PLUGS should have the Side Electrode polished smooth with a Dremel Tool.
DO NOT touch the Ceramic Insulator with anything, or premature fouling will be the result.
NEVER "clean" a Spark Plug, if it doesn't have a light tan color on the Ceramic Insulator, THROW IT IN THE TRASH.
Copper-Core Spark Plugs are dirt cheap, you should have 4 or 5 new ones laying around all over the place,
(still in the box), ALWAYS keep new Plugs in their protective box.
ALWAYS apply Permatex "Never-Seize" to the Spark Plug Threads,
they are threading into your expensive, soft, Aluminum Head.
Make very sure that you don't get ANY "Never Seize" on the Ceramic Insulator, or
any part of the Plug that will be inside the Combustion Chamber when installed, Threads only.
Follow the Spark Plug Manufacturers tightening instructions to the letter, ( for Aluminum Engines ).
Usually, finger tight, then 1/8 to 1/4 turn further with a wrench,
a used plug will have a metal gasket that is already crushed, so it will not want a full 1/8 or 1/4 turn to be tight.
Never over-torque your Spark Plug, a new Cylinder Head is expensive, and
a too loose Spark Plug may also damage the Cylinder Head Threads,
and may result in Splooge oozing out around the Threads, and
a too loose, or too tight, Spark Plug will not operate in it's designed Heat Range,
possibly causing early Fouling or Detonation.
6) Inadequate Oil Pre-Mix,
This "can" lead to increased Temperatures, but not always.
It WILL increase Bearing and Piston/Cylinder wear.
The ONLY advantage to running lean Oil Ratios is reduced Spark Plug Fouling.
Of course, going TOO FAR with the Oil could possibly cause excessive carbon build-up,
but modern 2-Stroke engine oils tend to do a really great job of cleaning up the deposits that they tend to leave behind.
Even if you have a bike with an Oil Injection System, I would run at least a 50:1 Oil mix in the Gas Tank,
this may also save your engine if something goes wrong with the Oil Injection System.
THERE IS NO SUCH THING AS "100:1" 2-Stroke Oil.
This "MAY" indicate that the Oil is high quality, or it might be just advertising hype. DON'T DO IT !!!
The Piston and Rings "MAY" survive it "ok", but the Crank and Rod Bearings WILL NOT survive it for long.
50:1 IS THE ABSOLUTE BARE MINIMUM OIL MIX for light, non-abusive, casual riding.
For max-effort racing, or severe conditions, 20:1 is recommended,
I don't care how much you paid, or what big name racer uses that brand of Oil,
it's totally foolish economy to scrimp on Oil.
These engines are running on the ragged edge of DETONATION in numerous situations.
DETONATION KILLS ENGINES, and
You can't hear it over a loud exhaust, especially with a Helmet over your ears.
It only takes a few SECONDS for your engine to be damaged or destroyed by DETONATION.
Detonation is a "run-away" condition.....
Once Detonation starts, it is self-accelerating, it gets worse with each passing second until the engine FAILS,
unless the Combustion Chamber is immediately allowed to cool down, and the pressure reduced, by closing the Throttle.
"Trace Ping" is the START of DETONATION, and if it is allowed to stop by closing the throttle,
it may only cause minor damage over time, and not develop into full blown, run-away, engine destroying, DETONATION.
Regularly reoccurring Trace Ping will pre-maturely "wear-out" your Engine,
and other than lack of Oil, is the main cause of Piston/Cylinder and Bearing damage.
It also costs you power.
Trace Ping is "usually" caused by sloppy Quench Clearances, ( Squish Band Clearances ) but ........
may also be caused by anything that may create a "Hot-Spot" in the Combustion Chamber, such as
a heavy Carbon Build-up, or too hot of a Heat Range of Spark Plug, or sharp edges on the Side Electrode of the Spark Plug.
Quench Clearances should be kept to LESS THAN 0.040 inch
On 125's and smaller, it can go as low as 0.025 inch.
This, of course, assumes that you have a "tight" engine,
and the Crank, and Piston Pin Bearings, are not worn-out,
and, you have the correct Piston to Cylinder clearances.
Trace Ping can be identified by very small dents, or tiny missing chips or pock-marks, on the Crown of the Piston or Cylinder Head,
it may also have the appearance of Sand-Blasting the Piston.
Basically, ANY surface damage on the Piston Crown or Cylinder Head is very likely from Trace Ping or short term Detonation,
( unless you're running with no Air Cleaner, or have Air Cleaner leaks )
If you notice these signs, you are one step away from a trashed Engine.
A carefully Blueprinted Engine, that has every step possible taken to avoid Trace Ping / Detonation,
and is always fed a diet rich in high quality 2-stroke Oil, will last for many YEARS, (not just a certain number of hours).
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
As for the one vs two ring debate.........
Single Rings will make, maybe, 1 to 2% more power because of reduced friction, but only at very high rpm.
Two Ring Pistons will make very slightly more compression, and therefore "slightly" more power, in the lower rpm ranges.
The Oil control aspect of 2-Stoke Rings is NOT a factor. (see the recommendations on Oil Ratios above),
If there is EVER actual metal to metal contact between the Piston/Rings/Cylinder,
IT'S TOO LATE, THE DAMAGE HAS BEEN DONE,
start planning on a re-build.
These parts must ALWAYS have a film of Oil between them, or INSTANT damage WILL occur.
The closeness of the rings to the top of the Piston "CAN" cause the Piston Crown to run slightly hotter,
but it's generally not a problem,
until detonation sets in,
in that case, the Single Ring Piston WILL FAIL FIRST,
but the 2 Ring Piston is STILL GOING TO FAIL UNDER HEAVY DETONATION CONDITIONS,
it may just last a little bit longer than the Single Ring Piston.
NOTHING will survive Heavy Detonation. ( this goes for cars as well )
If you want to see what it takes to survive "Controlled Detonation", go look at a Diesel Engine Piston,
they are massive and very, very heavy, that's why Diesels usually Red-Line below around ~3000 rpm.
And remember, that's carefully "Controlled" Detonation conditions, with lots of thick cast iron everywhere.
.
.
Great info. Thx
That's great advice Jim 👍 it amazes me how these gurus carry on about 50/1 & 100/1 ratios the more oil you put in a 2stroke the more power it will produce and last for ages 😃👍
Daamn you wrote so much but im only 10 like?
Good info, I always suggest to people not to trust oil injection systems, mix oil into the fuel ( I'm talking about older machines, not the latest oil injected bikes, which I would place trust in their systems)
My sons 05 kx85 is standard appart from dep system, it isnt as powerful all through bottom mid or high im powerband as better powervalve system in 98 to 00 kx80s but was rectified in 2014 85s with 16% power increase and new engine Powervalve also 2017 kx85 has 33% increase in power, but has signle ring piston.
However as my sons 05 kx85 has had alot money spent on it im hoping that advancing the timing to bring powerband in sooner will make it more fun agressive to ride, plus with the dep pipe that really overevs om top it may help also when advanced, it shoulndt cause problems advancing should it as long as i dont mess about with squish or head as long as bikes fairly standard right? Or if i port and polish?
Vegas, I bought a two stroke 'fixer-upper' about a month ago and when looking on youtube for answers and to learn more about the two strokes I see your videos all the time and get good answers from them. Thanks man!
Always wondered about why everyone insists on double ringed pistons. Great research.
In the air cooled days high revving engines had one ring. To reduce friction and heat and engine seizures. .slower reving engines had two rings
If your engine blows with a 2-ring piston, that's your fault for damaging the cylinder by riding it home. With a 1-ring you're forced to stay there until someone can pick you up, with a 2-ring you at least have the option of riding back
true, in a life and death situation the 2 ring piston can save your life!
For me you are saying True Words man i agree with you. Excelent video.
Thanks mate this makes my decision way better, I’m not stressed now
I really like how you do this brother. I go single ring. Thanks
The benefit of double rings is the increased ability to transfer heat from the piston to the sleeve. But just my understanding, mostly from liquid cooled sled engines.
good point.
Good video, well explained, thanks 🙏 (all the pistons that I use, from IAME to Rotax are single ring, at least here in Europe)
The oil ring in a 4 stroke is a scraper ring. It's job is to scrape the oil off of the cylinder wall on the down stroke.
it distributes a slim amount of oil. the oil comes in through the bottom underside of the piston, there are tiny holes that put oil from the inside of the piston out to the oil ring
Please make video about 4-stroke :)!!! You have great videos!
Thanks for the video . It makes u think on what ur buying
Glad you found it useful
Very good thought
I did inspect the piston prior to selling the 77 KTM/Penton 400. THis was an air cooled motor of course. I did not measure anything except for the ring end gap which was clearly excessive. The piston itself was unremarkable. It was sold/traded in 1985 for a 1982 Yamaha YZ 490 that I used as a dedicated trail bike here in Colorado. THe Penton spent its life in Colorado as a trail bike and was always plated therefore so many miles including lots of county road miles. I always kept the jetting crisp for altitude but never lean and used either Bel Ray synthetic or Golden Spectro oils. It never fouled a single plug. I ran a 40 or 50 to one mixture always.
thank u bro .. very useful
Outstanding review.
Thank you
Since the rate of wear in an engine is exponential to RPM increases due to the forces of inertia loading on the parts as speed rises, a second ring becomes a liability by its weight and the resulting heat it generates., Second ring creates enough friction at high revs to rob some power and cause heat. You can break it down to fairly simple choices. 2 rings for longevity and single ring for small cc / high revs / competition
AuMechanic thank god somebody who knows what they're talking about.
@@dirtboy896- Hes wrong" , the rings are the only way heat transfers to the cylinder wall,, then disapates heat to fins, or water , 2 rings more transfer of heat,
My fist 250, a suzook '86 rm250, was a single ring scream machine! I rode that thing, no rear brake, no kickstart, no prob.who cares.ride!
@@blackhat400
No, the top ring dissipates most of the heat to the cylinder wall, not the second ring.
Got it in one: I hope you get lots of reads on this vid, good advice.
My 1981 husqvarna has 1 ring but all my other 2 stroke engines have 2. Now i know why the did it. Thanks bud
Awesome.
OIL IN BETWEEN THEM IS KIND OF INVALID..
because we know that these rings are exposed to intake and exhaust ports.. meaning there will always be oil in between.. 👍👍👍
I've hade 3 rings setup, on a 2 stroke 70cc engine. The third ring was added by a mechanic witch did the grove on a machinery. That engine drove extraordinary for a very long time, and was no oil dosage re done just as it was set from the factory oil pump. And was air cooled to.
Have to say actually, that was a new cast aluminium piston, a bit more stronger .
Wow, I would never rim another gap in a piston they are weak and prone to cracks as they are, add another layer of unknown and you can easy get stuck in the middle of nowhere with a blown motor
For small engines ( less wearout of the engine, power loss cause of more friction, more stable piston and as such much less danger of getting piston wobble wich comes with vibration and tuned/enlarged stroke, less ring wearout and so much more time till service of the topend ->much better for streetuse but also doubled chance that a piston ring hangs itselfs in a port.
1Ring: Revs very high and fast, much higher wearout and as such more service is needed, slighty less compression, more chance of piston wobble caused by vibrations
This are my general experiences when comparing the 2 setups. General, 2 Ring Kits tend to have much lower porttimings and are aimed for daily streetuse while 1 Ring Kits are designed for racing and always needs more attention and good tuning.
Kits i used: Arisal 50cc TechPiston (Mahle/Vertex) 2 Ring, Derbi 50cc Racing 1Ring, Malossi 80cc MHR Team 1Ring, Athena 50cc Racing 1Ring, MVT 50cc Iron Max 2Ring, Stock AM6 50cc with Barikit 1 Ring Piston, Airsal 70cc TechPiston (Mahle/Vertex) 2 Ring
Thanx of the information
My 01 kx125 had a single ring piston I blew it up after like 2 years I was impressed I put a double ring piston in it and it has a lot of torque and the compression is way more then when I first rebuilt it with the single ring 😂
Very practical mate, thanks
Awesome Thanks for watching
Thankz for the info, ggz-
🚲💥☁☁☁👽👍
Cool
In my 54 years of mechanical experience, double rings lasts longer and seal better than a single ring. I guess a single ring is better for racing. Maybe?
I got 75 hours on that piston, I put a 5 dollar ring back in and got another 75. They do wear the cilinder less that's a plus power wise and stuff like that, I can't tell, all 2 strokes scare me
Pretty much all racers are single ring, less drag above 7,000 where every bhp
counts, but they get changed every few hours so....
@@vegasromaniac If you ride hard which I guess you do then you need to
change your ring at 6 hours, 10 hours MAX. No wonder you cooked your
piston. Get a Manual.
125 2 stroke = high rpm = less time for the gases on the top of the piston to push on the ring and cause blow by, therefore they use single ring pistons
250/300/500 ecc.. 2 stroke = low rpm = more time for the gases to cause blow by = double ring pistons (better seal)
also single ring pistons have less friction as you say, but don't last as long as the double rings, lubrication wise i don't really see problems with using double rings, with all the intake ports i think there should be plenty of oil between the rings
jnuxca well put he don't know shit about 2 strokes
my 23cc goped has double rings from the factory. noticed a difference with the single ring
It's more a compromise. Less drag, less seal, less life vs more drag, more seal more life. Choose your weapon.
Two thin rings in modern chainsaw engines. 1.2 mm
Single 1.5 mm is very common also. And minimal chamfer on the ports. Some factory port edges are sharp enough to cut your finger, but don’t cause trouble with wide 1.5 mm ring. I do a big chamfer on the exhaust and hand sand intake transfers.
Vegas blew his piston probably cuz of a combo of things...inadequate jetting and premix ratios with lame oil? Lubricate and Jet the bike properly for the correct cc / premix, shouldn't have any issues at all. It's F'n retarded that KTM calls for 60:1 premix for a 150cc, just sayin. Talk to Kelsey at RK Tek if anyone seeks real 2stroke expertise. More premix oil is best for smaller bore 2 strokes with 2 ringed pistons. My ratios for my 150 never go any higher than 32:1. More "good" oil, better compression, less blowback = cooler motor, more power. Never higher than 40:1 on my 250w either.
Oil is on the cylinder wall and lubricates everywhere, also between the rings
Exactly when I pulled off my top end I still saw the Machining between the two piston rings
off course ! you're right ! :)) ... well, seems our Mr. "Romanian" here is not the " sharpest knife in the box" when it comes to engines
the rings scrap the oil off the walls
If you have two rings--On the up or down stroke you have a ring scraping oil off. Therefore how would oil get between the rings if the walls are scrapped clean -=if the rings seal an explosion i'm pretty sure they keep oil out
stevecameron85 There is crosshatching on the cylinder walls that hold a film of oil
well explained
Obrigado pelo vídeo!
thank you so much for doing what you're doing, learning so much through your channel and I hope more people realise that your willing to experiment on your own motors etc does cost and I hope you get some decent sponsorship somewhere along the line... keep it up! awsome content!!!
Great talk! I don't really have a clue about single double. I just replaced my piston on a cr250 and dropped a double in. I ride a lot of single track in colorado mountains, always in the mid range rpm. My thoughts were two rings would help more on the lower range. Good stuff keep the videos coming!
Tha KS for watching
2 ring! I raced a wiseco 2 ring piston all year this year. No issues what so ever. Ask me for pictures
A piston ring compressor helps lol. That weight debate's funny. The ones that say that a two ring piston with it's rings are heavier than a single ring set up aren't taking the amount that has to be machined out of the piston for the second ring into account. I know the ring is made out of a heavier alloy than the pistons, but more material is machined out than is in the ring. And I agree that any difference there doesn't make any real world difference. I still prefer the 2 ring piston for trail riding and the single for racing as I refresh the race bike's top end more often.
I think you are on track. My 1977 KTM/Penton 400 had a single ring and never failed. Sold the bike with 7000 miles on the odo and the original piston and ring.
+DONALD OLIN wow, that is great to know. If true that changes everything. But still that many miles and not loosing compression, I'm already loosing some after 100 hours
After 20 years experience with a TZ250, RD400 and many other 2T bikes I'll explain my experience. Secondary compression does not change with ring count, that is pressure between the piston and combustion chamber. Primary pressure being crank case pressure. 2 rings will make the cylinder wear faster if using iron sleeves or chrome plated bores but not nikasil. Nikasil is. To F-ing hard. A single ring setup the ring will wear faster then the bore. Ex: an air ccooled RD400 can get a third more hours on a double ring piston vs single but the bore will wear slightly faster. The most notable differences are Skirt wear and friction. A single ring will create less resistance and make more power in return but the lifespan is a lot less. You may only get 2 or 3 sets of rings before the skirt gets scored. Scoring can happen on either intake or exhaust and there are many reasons for this. We. Have found that twin ring pistons stay strait better in the cylinder than single but in racing the piston and rings are changed out so often that skirt wear is irreverent. Nikasil bores are porous and stay lubricated very well wich refuses wear and. Helps keep things cool. I think most bikes today are either one or the other so if you wanted to experiment you would have to use a piston from a different bike. A side note, my neighbor builds custom chainsaws and he says he can get higher chain speeds in the cut with a single ring piston, he had me modify a few dirt bike pistons for him to.
Good to kow
Bernie: great common sense from experience... I hope this gets a lot of reads.
Can I ask you to make an video witch wil explain difference between aluminium and cast iron air cooled cylinder. I have a loot of questions about that, like wat is the heat difference, durability, can piston have higher rpm in aluminium cylinder, how it performs. It will be very helpful.
They put 1 ring on alot of 125s to reduce drag and reduce wear at top dead center , and bottom dead center due to very high rpms . The gaps in the rings don't create hardly any compression loss , the gas goes into the gap and behind the ring to push it out and create a tight seal under running conditions , wich is why a gap to the high end / widest tolerance within specs is always better than to tight . The 2 ring style is what I prefer though , I've never had a problem . The 2 rings do hold compression longer . The top ring gap always needs to be gapped wider than the second . And most people don't realize that the ring to ring land flatness and tolerance is a HUGE factor to blowby and compression . That's why when a ring sticks you have no compression and then simotaniously damage happened . Rings and grooves need to be very clean to work 100% .
Tip of the day.
Clin clank clin clank, if you hear this, Stop engine and tow it to shop.
You can save 500$ by using this tip of the day.👍
Thanks for sharing V. R. Interesting video.
I have a 1995 kdx 200 and it has 2 rings. Its only had 1 other piston and rings in its life. Ive put easily 200+ hours on the current top end and Ive had zero issues with it, no power loss, no compression loss. Nothing. I think the current piston i have in it was put on it 2006 or 2007 and its never needed anything since
How good are namura pistons. I race about twice a month and when I’m not racing. I’m practicing
Very very good
I ride a KTM 250sx, put over 60 hours of just trail riding this summer on a 1 ring piston, had 0 problems. I just did preventative maintenance for the topend and it looked great! I actually bought the identical piston kit and slapped it in, 1st kick ready to go. I’ve always ran Namura pistons never had any problems, Weisco on the other hand can kiss my tailpipe!
+Timzy yep, I got 90 on mine and I'll run it till losses compression
I'm rebuilding my 95 cr250 and was gonna go with a hotrod crank and wiseco top end. Seen the namura pistons on ebay for almost half price, so I figured they were junk. You say you like them better than wiseco?!!? I thought wiseco was pretty much top of the line no?
Big Worm Wisecos are forged (stronger than cast) and are more dense. Because they are more dense, they have more thermal expansion so they need to be warmed up slower with the cylinder to prevent seizing. Just let your bike/sled warm up before WFO.
Wiseco I wouldn’t recommend for any two stroke...cast pistons tend to hold up better...however let’s not throw the baby out with the bath water, I’ve run Wiseco forged pistons in 4 strokes for years with zero issues...You just need to follow the instructions and do some simple math with a Calculator and make damn sure your ring end gap is specified to wiseco standards and not the manufacturers
Bought a Namura piston and it cane with a pit in the skirt, rust on the ring pins, terrible casting inside, wiseco is well worth the price if you care for your bike, a wise decision if I might say lol
If your bike starts easy when warm but hard to get going on a cold start, you need new rings, dont wait till you blow rings out to rebuild, if it blows a ring prematurely, you have a port lip that is grabbing rings. This can be from heat warping the surface or a sharp edge after honing. A good champher will help, and honing with straight stones will rub high spots first and show you what needs work in the first few strokes of the hone. Also if the ports have webs the web can get hotter and expand more grabbing rings, so i sand those a little after honeing
Great videos, have tried using a ring compreser?
not gunna work well on a small 2 stroke where the cylinder is installed after the piston
I have a 100cc bbr..the piston is designed for 3 rings..I lowered it to two rings and still thinking about just running one ring..been a great engine but does seize up often after a hard ride..
one thing you may have over looked is the drag between 1 and 2 rings. 1 ring has less drag and will rev quicker and even has better torque at low tpm below the pipe. 2005 cr 250 came with one ring and after some motor work by Varner Motor Sorts and conversation i went with the one ring later on during a rebuild i tried a 2 ring piston and I was a believer in one ring after that. and the you dont loose much longevity unless you are a really fast and hard rider.
NA buddy, he mentioned that 1 ring is less drag, I heard it clearly....
Big Worm did I not say that. Second sentence, third line.
NO SHIT SHIRLOCK. I was saying that he said that in the video. You said he overlooked it but he didn't...... sorry for the confusion mr tidwell
Well my professional rinken mods built motor has a single ring and has a hundred hours on it and I run Castor927 nothing but n still a beast
i change the piston for 25 hours right now. When is it reasonable to change ktm 125 sx , i ride on a track
i would just use what the bike come with stock. the manufacturers have spent millions on researching whats best so i would just go with that
My seven year old loves the vids. He likes learning and thinks you sound like Gru from Dipicable Me.
Awesome....
I have yz 125, using for wood\trail riding. What pistons better for me, two or single ring? thanks =)
I run 1 ring in my twin ring piston which i have done for many years checked compression always consistent..
I run single because I ride a cr125 and it doesn't produce much heat and the single doesn't wear the cylinder as fast but I have to replace it every twenty hours and my bike produces the most compression out of any 125 2stroke mx bike just the specs also nice vid subbed!!!!! Also the single helps the bike rev a little faster and higher and since it's a 125 it lives up high.
i think a single ring and light flywheel definetly will make the throttle more snappy. had both on my yz125 noticed a difference. i could get 40 hours out of a single ring riding hard mx I used an advanced synthetic oil at 70:1 ratio
Like the video. Raise good questions. I'll take that advice to not limp the bike back. I ride with people always. Towing is better. 😎
every time the piston goes past the inlet port it sould get some lubrication if u have the correct setup carburetor it will be lubricated
Why it is important for motors to idle. At the end of the longest straightaway when you lift. No idle..no more fuel..no more oil...
@@bigrich7026 yeah but theres no way to escape that
How about lubrication holes at the exhaust bridge? Saves on expansion problems by cooling the bridge.
its not to cool its to lubricate the bridge with the oil that goes in to the lower chamber
nice video !
what is your opinion about Namura?
working on the videos as we speak , will come soon !
Red Bob namura is junk!
Single ring , high rpms and race applications, double ring, woods/ trail riding.
Also 500 for a bore and honed on a single cylinder your getting ripped off.
One way looking at it
@@vegasromaniac Re-bore? I'd pay $200 inc new piston.
I also ride at my house all the time
I would like to see a video on forged pistions
Mee too
On a 4 stroke' the oil ring is the bottom ring 'the first and sectond rings are only for compression .
my weedeater VS2000BV 25cc 2 stroke blower has only 1 ring
I noticed on my sons 2 stroke air cooled and water cooled KTM 50s both had single piston rings. You think mostly less friction due to the small displacement??
I think the pistons are too small to fit 2 rings, but that's an interesting point.
what about ring flutter. thats a huge difference between 1 and 2 ring. ends up like a rev limiter for 2 strokes. great video.
Which one has more flutter? I guess you're talking about the "one ring" option right?
That's one very good reason why pretty much all 2Ts for us are red-lined at
11,000 rpm or less. Above that the risk grows exponentially. The risk is the
same for racers but hey they change everything after each race so...
You won't get 100,000 miles from your 250 2T if you always run it at 13,000.
Sounds good I agree, but... And there's other reasons too. Don't go there.
in most 4 stroke engine second ring clearence is wider than 1st ring. that makes power is loosing to much and smoke as well and rider must quickly legalizing it when 1st ring failed. but in 2 stroke??
If the piston crown is damaged the cylinder is destroyed regardless of number of rings. You have to bore the cylinder for a new piston even if the sleeve has minor scratches.
Boom
Why wouldn't there be oil in between the rings?
Honda Cr 500 due to top ring pushing the oil up away and the bottom ring pushing the oil down away. There would still be some residual oil on the cylinder but not as much as above and below. I understand what he is thinking. However in that small gap between rings I would think that there would rarely if ever there would be any contact from the piston to the cylinder wall. The double rings should help further with piston alignment until they are too wore to do the jobs intended. Maybe this will help you to wrap your head around it. Definitely hard to say which is better and to be honest nothing that I think about when buying a new piston. Whichever piston they have in the shop is usually the one I'm going home with to fix my bike.
UnlinkedCashews yeah that's a lot I've seen people drill holes in pistons to lighten them up and for the exhaust bridge
The oil ring isnt to lubercate the rings its to keep oil from the rings also oil does get between the rings on a 2 ring 2 stroke
Kolton: of course you're right.
My 1975 2 stroke 75cc came with 2 rings but had a wavy spring-steel expander behind the 2nd ring to increase tension. I took it out...
Interesting
Bad move.... the manufacturer knows better than you dude, put it back.
D NY it’s not stock, revs a lot higher. I’d say WE collectively know a lot more than the manufacturers did about 2 strokes in 1975, when expansion chambers were barely developed and most people ran 30wt in their 2 strokes
NEED BIGGER JETS and not so much time wide open or put a thermal couple on exhaust to monitor your temp. Things do not last long @ 500C.
I run that same numara piston in my yz250. What did you do to blow it up like that? Jetting, oil mix, and oil brand?
Yeah something was wrong with that bike, don't know what..
You. Would think that more rings would provide more compression but in my experience with the correct size of a quality piston in a good bore it won't. You can get both style pistons for the TZ250 and both make the same compression. Remember a 2 stroke has a lower compression ratio. Than a four stroke
Yes but I also had a 4 stroke with one ring and oil ring, and still run like mad
Calculating compression ratio on a 2T is tricky and not comparable to 4T compression which is very easy to calculate. 2T compression is guesswork.
So will if there was ever a 2t piston with 3 rings would that lube better like the 4t piston but be better than the single and double 2t piston, be good see experiment.
Also was told my sons 05 kx85 had new piston in 4hrs, since we owned it done 5hrs mainly on tick over in garden 5mins once a week untill weather better. Will it benifit from a new piston and ring or rings just for peice of mind?
The 4 t has a oil ring that is quite complex
Check the manual, this chap wouldn't know.
I have my Gilera Runner with 1 ring piston :D
regardless if its a 4 stroke or 2 stroke, the top ring is the deal that seals compression ,on a four stroke the second ring is just a scraper blow by is a fact of life (ring gap) has alot to do with it
Yeah for me rule of thumb is 125 cc and smaller use 1 ring 250 çc and up 2 ring! 👍 braaaaaaap!
if i had a 2 stroke i would run single ring flat crown pistons if flat crown was an option, i like that the bike lets me know it has a problem before i take it 200 miles away and it fucks up, i ride alone now cause my friends moved away, actually i do have a 2 stroke but its tiny, its a yamaha pw80 but still can put single ring piston in it as well as a 2 ring and i have a new piston for it when it goes out and its a single ring if i remember correct, and as far as i know flat crowns scavenge better at lower rpms and perform damn near almost as good if not as good as domed pistons at high rpms and i just like them better for some reason even if they arnt better, i feel like cause they are flat with a machined finish over a domed piston with a cast finish it would handle carbon buildup better
turns out flat pistons scavenge worse at low rpm, just went and refreshed my memory. nobody ever accused me of being an expert
Seems to run ok the 85 very fast with me riding it
Yeah contrary to what other people believe 2-stroke don't really care about gas especially when they're used an older and they don't have all the compression
okay 2 rings more drag 1 ring wears faster less drag. im going to try a 1 ringer.
Kevin: That's true only above 7,000. Really you need to go 10-11,000 to have
any benefit and it isn't much but for Racers every BHP counts.
No oil between the 2 rings? I believe that is a lie. There must be oil between them. Every time the piston let's air, fuel and oil into the engine it lubricates itself between the rings. The same goes when opening the exhaust port. Negative pressure lubricates the engine with fresh gas mix.
Yeah but it doesn't get between the rings only what is left on the sidewall from the previous burn
That N tho. You should have use Wiseco
And I hope you fattened up the jetting so don't keep popin pistons bro! Braaaaaaap! 👍
I got a 4tx problem solved
I got an 1987 kx 500 it’s on it’s factory single ring piston
I have a 1995 kdx 200 and its only had 1 other piston and rings, previous owner did top end (i have papers) and i think he put it on in 2006. Ive put easily 200+ hours on the top end thats currently in it, runs great
So witch one is better for a 2 stroke and how long do they occasionally last for ?
2 ring better, good for about 150 hours. 1 ring about 80 to 90hours
This video clip is a good case of overthinking things ... The engineers who designed your bike's engine have done far more testing then you ever can , so if your piston kit comes with a single ring or two rings , just put them on , put your bike back together and go riding . If you race , then maybe , but otherwise don't spend a lot of time on this subject ... imo
IMHO too.
The only significant difference I see between 2 and 1 ring is the end gap on the ring. With a single ring some small amount of combustion gas can leak past that small end gap. With 2 rings, the second ring stops any leakage because the rings are not aligned with each other. All of the things cited look like salesman BS to me.
i would think youll get less piston slap on the cylinder with 2 rings . id rather have 2 rings
he used a numura piston that's why the top of it was broken.. they bad .
Gerson Ruiz okay listen, im sick of ppl saying namura sucks, on the back of the box you need to read the "FINE PRINT" they specifically say to have a "TRAINED PROFESSIONAL" install the piston and piston rings, i have a namura big bore piston on my 2001 yamaha warrior 350 6-speed and it has much better compression, and i have never had a problem on it, quit hating namura
Lol! Take it easy, man.
Mark Alan sorry but people need to understand that there are words for a reason
I've never bought Namura pistons before. So I couldn't tell you from personal experience. The low cost actually scared me into thinking their cheap quality junk, not a chance I'm eager to take when it comes to engine reliability. I've heard from several people Namura does make quality products though. I would usually buy oem. I've installed Wiseco a few times. But for the most part I think Wiseco is overrated.
Maybe I'll give Namura a shot though. My daughters Pw 50 could use a fresh top end.
He over heated the piston by running wide open to long. The exhaust port is where it disintegrated. LEAN it out.
My 1984 2 stroke motorcycle has 3 rings. It is still running the original rings.
You tested the compression?
Regularly test it with my left leg, it passes that test. I had the motor apart 2 months ago to replace a worn third gear. I measured the ring gap and bore. Still within tolerance. I have owned this bike from new, it has only done about 60000km.
9:58 half a hp on 50cc is important
Haha yeah... It's double
@@vegasromaniac good 50cc produces about 9hp
@@ghazik3656 70cc airsal one piston ring 11.7 hp
Four strokes don’t have oil rings in between rings the top ring then the 2nd then oil control rings 👍
But if it blows up. Why drive it home?
If the piston fails it is a defective piston, or your rings are hanging up on a port edge, or wrong spark plug heat range, or you have a lean tune, or you have the wrong mix ratio, or you have an air leak, or you have detonation because the timing is off, or the octane is too low, or your bike was running too hot and overheating, or you are not warming up your two-stroke before getting on it and are causing a cold seize, or you don't have sufficient cross hatching to hold the oil, or your piston has too many hours on it, or the piston was installed backwards...or
Wow I guess if you don't know the facts opinions are valid, amazing
Adam: you jest..... LOL
in a 4 stroke engine the arrangement is 1st ring 2nd ring and the oilring. you mentioned is 1st ring,oil ring,2nd ring your wrong
Danilo: he doesn't know anything about bikes, he's obviously never seen a 4T piston.
A Namura piston that grenaded... What a surprise.
The wiseco did first. Than namura after something was wrong with that bike
My bike has 3 ring pistons but it does have a low revving high torque high compression 2 stroke motor.
MZ?