This is a great explanation. I’ve always known what the power valve does, but I’ve never understood precisely how it does it until this video. Great job man.
Great vid. Good to see some one going deep enough on the technical subject and not just scratching the surface of it. You deserve more traffic on your vids!
I started racing go-karts in 1960, two stroke 100cc motors. We used crank case stuffers and dual carbs. Expansion chambers were not in use yet. Started racing MX in the 70s, two strokes again. Reed valves and x-chambers came along. Started racing SCCA sports cars after that and quit paying attention to two stroke development. Thanks for helping me get up to speed!
I appreciate this in depth explanation.. I’ve recently just started wrenching on 2 stroke engines and this is the kind of stuff that’s helping to educate me.
Thanks. Snowmobiles use a different exhaust valve, it’s a guillotine valve that slides up and down, but uses the same principle of restricting the exhaust port size at lower rpm and expands it at higher rpm. It was a total game changer for snowmobiles
I had a 1984 Cagiva 125 without PV. Made about 10hp up to 7500 when, like a light switch, the hp went to 20+at 7600! It was impossible not to spin the tire, i tried many times. Made around 30hp but the power band was about 2000 rpm.
Thanks for the great explanation. For such a simple design, in appearance, the two stroke is a very complex system. Four stroke operation is easy to consider, but the resonances involved with a two stroke makes me think about the pulsejet engines.
Before exhaust valve, some manufacturers were using rotary intake valve. I tried one Rotax with "enduro valving" and another with "mx valving" and there wasn't a jarring difference. Eventually all manufacturers went to reed valve and maybe an exhaust valve for power cases.
I have a kawasaki rotary valve enduro. The rotary valve has significant more torque on the bottom end compared to reeds. Reeds however have much better top end efficiency.
My 250 Can Am MX which was road registered revved out superbly. Much better than a Japanese 250 MX. But bottom end was inferior. I guess the disc valve can be cut to have longer intake time.
Not exactly. A stiffer spring will give you the impression of a higher power output because it will suffer a more abrupt power increase, but not a higher power output per se.
It gives the most efficient power output and the desired one by the manufacturer. I would recommend adjusting the spring preload, but I wouldn't change the spring. They know what their doing 😄
Buenas, tengo una yz125 1991,pero no tengo repuestos para la valbula de poder, el cilindro puede ser remplazado por el de alguna version mas nueva? asludos!
The power valve is a vital upgrade but the revolutionary feature was adde earlier. That was the resonator exhaust which was made by a former v1 rocket engineer worked for the MZ in the motogp. Suzuki, which was the weakest brand in the gp for the time managed to get the resonator exhaust plans (they stole it throught the engineer and a young pilot borrowed from the mz..) after that suzuki became the unbeatabe brand for a decade. That was the key momentum, without the resonator the 2t was not stronger than a 4t with same displacement. With the new exhaust the engine was able to rev 2x higher and so producing almost double power. Now that wss revolutionary.
Thanks. Looking at your graphs: if increasing preload for more progressive power has the effect of reducing low/mid range with no benefit on the top end power, who would use it and why? Cheers.
@@StepstoPodium so, would you say mx wants snappy power with the idea of keeping it always in the power band (and perhaps for jumps?) while enduro wants more linear power for control at low rpms?
Nice explanation, but if you permit the ypvs was electronically controlled by a servo motor. The kips system by kawasakie was a manual system. Great vid .
Thank you! 🙂 I'm almost certain thatcthe ypvs, or at least the first version of it, was fully mechanical. At the time of the making of the video I did an extensive research and don't remember having any ellectronics involved
@@StepstoPodium thanks for the reply. When i started i put a green spring in with the pre-load screwed in too. Now I'm riding better my engine is running very hot and have hanging rev issues. Might be an air leak but i'm looking for other reasons too.
I understand everything except one thing. When the fresh gasses are let into the combustion chamber, some of it escapes into the exhaust port, as is demonstrated in the video. However, it looks like the exhaust gasses are pushing them back into the chamber. What causes this? How can the exhaust gasses just reverse themselves? Aren't they supposed to flow straight out of their port and not flow backwards?
It’s the reason that 2 strokes have their fat pipes. Exhaust fills the expansion chamber then gets choked way down at the back, so the exhaust pulses bounce back toward the engine and that bounce back pushes the unburned fuel back into the combustion chamber
So that is why bigger 2 strokes feel way smoother I was always used to tuned moped engines producing anything between 15-26hp, these engines are set up to give almost no low-mid end power and when it hits the powerband the difference is just brutal
They opened the door for wider range power efficiency. The early attempts with actual Leprechauns proved difficult to maintain and impracticable. They were fine when not drinking but that didn’t last long. A governor system to provide control allowed to more precisely time the exhaust intake phases. That thing hooked up when it came on the pipe. A barking power band that liked to rev.
That is the problem with Leprechauns, clever and amazing workers until they get a whiff of alcohol. That's why they had to remove all the Leprechauns who operated the power valves when ethanol fuels were introduced. When you find four Irishmen together, you will usually find a fifth!
The piston does not determine the intake timing in a reed valve engine, only a piston port engine used before the mid 70's. Would you like to consult with me before you make a historical vid? I am only 1 min in, and corrected you 3 times already.
Wow now this was the best explanation i have ever heard and seen i have been looking for something like this really awesome stuff thank you big thumbs up 👍👍👍👍
Hi love your channel got a question and i have asked around and done some research but no real solid answer i want to build a two stroke engine from scratch and yes re-engineering the wheel i know. But im battleing to get a awnser on why brush cutters uses flywheel /magneto and ignition but motorcycle!/bikes uses all that and a cdi if i build a performance two stroke and just ad a flywheel and ignition coil from a brush cutter, two stroke lawnmower, leaf blower wil it work? as mechanical things is easy but electronic things im not the brightest crayon in the boxs Just for the challenge my lower end is from a old kx 125 1985 thats is my base that im working from all the other stuff is missing... 😜
My friend passed away when this velve open on kawasaki 150 ss , gas cable stuck and cant go back at 140 km / hour and more faster and faster , its happen quick no time to react or thinking , so first instinc was push back brake and lose ballance then he fell off
I've heard mechanics suggesting to just keep the powervalve open at all times by thread locking the mechanism and removing some parts. Do you think it's a good idea?
The only reason 2strokes are gutless at low rpm is they're purposely deprived of air flow.. That's all the ''power band'' is doing it just lets the engine actually take a gulp of air .
@@StepstoPodium Not size, but location. more precisely - the location of the upper edge of the exhaust window - the angle of its opening. this is what ypvs regulates. True, this is already boring on my part, but in the past, such an explanation, your explanation, misinformed me for years.
First off, I politely disagree. The port timing, the holes in the cylinder, a- "PRE PROGRAMMED PERFORMANCE CURVE, Is what controls it. The piston only ENABLES this performance curve. Proof? CHANGE THE PISTON ALL YOU WANT- won't change by much. Change toe port size and timing in the cylinder- and your world changes!
Been riding 2 strokes since I was a kid…30 years later I finally fully learn and understand how a power valve works
Glad I could help! 😄
This is a great explanation. I’ve always known what the power valve does, but I’ve never understood precisely how it does it until this video. Great job man.
Thank you for watching! Glad I could help 😄🙌
Great straight forward explanation....how can I bolt one onto my trusted Honda C90...
Least you don’t think power band is a part😭
1:15 that was the best explanation of how 2 strokes work i have seen.
Thank yoouuuuu 🙌
Best video on how power valves work
Great vid. Good to see some one going deep enough on the technical subject and not just scratching the surface of it. You deserve more traffic on your vids!
Thank you so much John!! I really appreciate 😃🙌
I started racing go-karts in 1960, two stroke 100cc motors. We used crank case stuffers and dual carbs. Expansion chambers were not in use yet. Started racing MX in the 70s, two strokes again. Reed valves and x-chambers came along. Started racing SCCA sports cars after that and quit paying attention to two stroke development. Thanks for helping me get up to speed!
Thank you for watching! 😄
excellent!! what actually opened and closed the exhaust valve (and what the stiff/soft springs do) was a complete mystery to me until now.
Glad I could help 😁 little by little, a dirt bike becomes an understandable machine instead of something with leprechauns inside 😂
I appreciate this in depth explanation.. I’ve recently just started wrenching on 2 stroke engines and this is the kind of stuff that’s helping to educate me.
Thank you for watching and glad to know! 😄🙌
Thanks.
Snowmobiles use a different exhaust valve, it’s a guillotine valve that slides up and down, but uses the same principle of restricting the exhaust port size at lower rpm and expands it at higher rpm.
It was a total game changer for snowmobiles
Now i understand what those different coloured KTM power valve springs do!
AMAZING VIDEO. Kudos to Yammy dudes for "Mo pOwA BAbAE"!
Rebuilding my first two stroke that has a power valve, this helped so much! Thank you!
Glad I could help! 😄
Very nice description of the functionality of the power valve system! Knowledge is indeed Power. Gracias!
Thank you so much Jeff!! 🙌😄
Well done, this helped me understand exactly what the PV does. I have a 99 KX500 and 2002 KDX200.
Glad I could help! 🙂🙌
Those are great bikes. Have ridden both before.
You have some of the best "How motorcycles work" video's on youtube.
Thank you so much man!! 🙌🙌💪
Great video, and clear explanation, the addition of history to the tech is nice too.
We can't appreciate the technological evolution if we don't know where we started, right? 🙂
Thank you for watching!
Great video! I just watched a few videos on this and yours was by far the best and easiest to understand!
Thank you so much!! 🙌
Great explanation of how a power valve works. I also enjoyed your videos on how suspension works. Please keep up the good work informing us!
I appreciate it Stephen! Thank you so much for watching! 😄🙌💪
That was the best explanation I’ve seen of how a power valve works.
Thank you so much!😄🙌
How do we notice or determine if our motorbike has the powervalve issue? what are some symptom or signs?
Very low performance through the whole power band!
I had a 1984 Cagiva 125 without PV. Made about 10hp up to 7500 when, like a light switch, the hp went to 20+at 7600! It was impossible not to spin the tire, i tried many times. Made around 30hp but the power band was about 2000 rpm.
Bro said a 1984 125cc bike without a power valve can make 30hp😭 more like 20 on a perfect day
@Willy_Wanka not really, I've got a 1984 dt125lc and it makes about 24-25hp at 7-8k rpm
Well said. Simple, precise and to the point.
Thank you for watching! 😄🙌
Sooo smart to use centrifugal force 🤯
Great explanation man 🤙🏽
Thank you Tony! 🙌
Thanks for the great explanation. For such a simple design, in appearance, the two stroke is a very complex system. Four stroke operation is easy to consider, but the resonances involved with a two stroke makes me think about the pulsejet engines.
Thank you!! 🙌😄
Before exhaust valve, some manufacturers were using rotary intake valve. I tried one Rotax with "enduro valving" and another with "mx valving" and there wasn't a jarring difference. Eventually all manufacturers went to reed valve and maybe an exhaust valve for power cases.
I have a kawasaki rotary valve enduro. The rotary valve has significant more torque on the bottom end compared to reeds. Reeds however have much better top end efficiency.
@@awesomecooly123that's a trail bike.
My 250 Can Am MX which was road registered revved out superbly. Much better than a Japanese 250 MX. But bottom end was inferior. I guess the disc valve can be cut to have longer intake time.
Great explanation! Enjoy your channel. -Nevada USA.
Thank you Jake! 😄🙌
I always wondered how a power valve works, not any more👌🏻
😁💪
Great job again, keep up the fantastic work!
Thank yoou Nigel! I really appreciate it 💪🙌
Bro, siempre te lo digo, pero tus vídeos som impresionantes. Sigue así!
Muchissimas gracias tío! 🙏💪A ver si al final de algunos videos todos nosotros entendremos nuestras motos como si fuera una bici 😁
@@StepstoPodium so less stif spring give high power in low rpm & more stif spring give high power in high rpm.?
Not exactly. A stiffer spring will give you the impression of a higher power output because it will suffer a more abrupt power increase, but not a higher power output per se.
@@StepstoPodium so your final answer is
Default factory strength spring it give the best performance power
Is it?
It gives the most efficient power output and the desired one by the manufacturer. I would recommend adjusting the spring preload, but I wouldn't change the spring. They know what their doing 😄
Buenas, tengo una yz125 1991,pero no tengo repuestos para la valbula de poder, el cilindro puede ser remplazado por el de alguna version mas nueva? asludos!
Great video with easy to understand contents..
Thank you! 🙌
Talvez o canal mais Underrated de sempre 🙆🏼♂️
Obrigado pelos videos excelentes. 👍
Muitíssimo obrigado Frederico! Obrigado eu por veres os videos 👌🙌💪
Great explanation.
Amazing video. Great teaching skills.
Thank you!!!
Great helped me out a lot definitely gonna share you to my other riders🙏🙏
Thank you so much Ernie! 😄
The original Yamaha YPVS used a rotary valve controlled by a servo motor and electronic control unit.
Cool man u should do an explanation of the 4 brands and their differences thru time up to the present
I did not know about such a mechanism. Interesting.
The more you know...! #knowledgeispower 😁
Very well explained Cheers Mick
Thank you Mick! 👌✌️
Ai essas ilustrações... 🤤🤩 Muito bom como sempre! 💪
Muito obrigado Zé! 😄 grande abraço 💪
Awesome video. Thank you.
Thank you for watching 🙂💪
Love the channel man thanks!
Thank you for watching! 😄
The power valve is a vital upgrade but the revolutionary feature was adde earlier. That was the resonator exhaust which was made by a former v1 rocket engineer worked for the MZ in the motogp. Suzuki, which was the weakest brand in the gp for the time managed to get the resonator exhaust plans (they stole it throught the engineer and a young pilot borrowed from the mz..) after that suzuki became the unbeatabe brand for a decade. That was the key momentum, without the resonator the 2t was not stronger than a 4t with same displacement. With the new exhaust the engine was able to rev 2x higher and so producing almost double power. Now that wss revolutionary.
Another brilliant video! Congrats
Thank you so much Francisco! 😄💪💪
great video and great explanation, please do more!!
Thank you!
Thanks. Looking at your graphs: if increasing preload for more progressive power has the effect of reducing low/mid range with no benefit on the top end power, who would use it and why? Cheers.
Some applications/riding requires a more snappy feel or response of the engine!
Not necessarly a bad thing, simply different
@@StepstoPodium so, would you say mx wants snappy power with the idea of keeping it always in the power band (and perhaps for jumps?) while enduro wants more linear power for control at low rpms?
@miro_s exactly!
Awesome video 👍🏻👍🏻👍🏻
thank you!!
Nice explanation, but if you permit the ypvs was electronically controlled by a servo motor. The kips system by kawasakie was a manual system. Great vid .
Thank you! 🙂
I'm almost certain thatcthe ypvs, or at least the first version of it, was fully mechanical. At the time of the making of the video I did an extensive research and don't remember having any ellectronics involved
Another wicked video my man!
Thank you so much man! I'm glad you enjoyed it 😄
How have the design of power valves evolved since then up until modern bikes like KTM? Are they more complicated now or still the same as your video?
Fairly similar :)
The person who figured this out was a genius for his time.
True indeed!
Another aweosme vid!!
And some new ones are coming out really soon!!
So, on GasGas Ec300 to delay the PV I need a harder spring, not just a screw adjustment, right? :)
If you don't have an adjustment screw, yes!
Excellent, excellent, excellent (as always). The dynamic graphics really help and Indiana Jones is a nice touch :-) Obrigado pelo video
Thank you Ariel! As always, never skipping a video! 😁 Top supporter 💪💪
(Thank you for your extra effort with the Portuguese language 🙌🙌)
Can u make a video on how air suction valve works? Or air intake system of motorcycle for euro 4 compliance
Where can I buy the clip holding down the rod
Sherco uses an electronically controlled motor driven system to actuate the power valve so you can change how it opens by reprogramming the ecu.
Exactly 👌👌👌
Awesome vid thanks
Thank you for watching! 😄
if the power valve is restricted due to using the green spring screwed in, can this cause over heating?
That's a really good question. It can!
@@StepstoPodium thanks for the reply. When i started i put a green spring in with the pre-load screwed in too. Now I'm riding better my engine is running very hot and have hanging rev issues. Might be an air leak but i'm looking for other reasons too.
Great video
Thank you!
I understand everything except one thing. When the fresh gasses are let into the combustion chamber, some of it escapes into the exhaust port, as is demonstrated in the video. However, it looks like the exhaust gasses are pushing them back into the chamber. What causes this? How can the exhaust gasses just reverse themselves? Aren't they supposed to flow straight out of their port and not flow backwards?
It's all thanks to the back pressure wave. I've got another video clearing that out 😄👌
It’s the reason that 2 strokes have their fat pipes. Exhaust fills the expansion chamber then gets choked way down at the back, so the exhaust pulses bounce back toward the engine and that bounce back pushes the unburned fuel back into the combustion chamber
Can you do a video about TPI vs TBI? And electronic power valve?
Eventually, yes 😅 the EPV is definitely on the radar. Just waiting for the conditions to meet 😁👀
You're a genius! Thanks! 👌👌
Thank you for watching! 🙌💪
Later on these became electronically controlled.
Remember back in the 90's on my bike, when I turned the key, the valve cycled through it's motions.
thank you!
So that is why bigger 2 strokes feel way smoother
I was always used to tuned moped engines producing anything between 15-26hp, these engines are set up to give almost no low-mid end power and when it hits the powerband the difference is just brutal
Cool channel. I subscribed
Thank you Tony! 😄🙌
They opened the door for wider range power efficiency.
The early attempts with actual Leprechauns proved difficult to maintain and impracticable.
They were fine when not drinking but that didn’t last long.
A governor system to provide control allowed to more precisely time the exhaust intake phases.
That thing hooked up when it came on the pipe. A barking power band that liked to rev.
😂😂😂😂😂 loved the comment 👌😄
That is the problem with Leprechauns, clever and amazing workers until they get a whiff of alcohol. That's why they had to remove all the Leprechauns who operated the power valves when ethanol fuels were introduced. When you find four Irishmen together, you will usually find a fifth!
Thank you sir
Thank you for watching! 😄
Bro just taught me more in 6 mins than I did in 4 yrs of high school
Thaaaaank youuuuu
Muito bom como sempre!!! Já agora o sistema da RCvalve da Honda não é bem igual pois não? Penso que que não dá para ajustar!
Muito obrigado João! 💪
Assim de repente não estou a ver qual sistema é 😛
@@StepstoPodium è o sistema Powervalve das Hondas CR250 2T que penso que seja eletrónico e que não é possível ajustar.
The Jones family in the USA were the major development of the YZ's in the 70's, including the power valve.
The power valve did not hit Yamaha production until 1982. I think you have it confused with the reed valve.
The piston does not determine the intake timing in a reed valve engine, only a piston port engine used before the mid 70's.
Would you like to consult with me before you make a historical vid? I am only 1 min in, and corrected you 3 times already.
Wow now this was the best explanation i have ever heard and seen i have been looking for something like this really awesome stuff thank you big thumbs up 👍👍👍👍
Thank you so much!!! Enjoy the channel! 😄🙌💪
Hi love your channel got a question and i have asked around and done some research but no real solid answer i want to build a two stroke engine from scratch and yes re-engineering the wheel i know.
But im battleing to get a awnser on why brush cutters uses flywheel /magneto and ignition but motorcycle!/bikes uses all that and a cdi if i build a performance two stroke and just ad a flywheel and ignition coil from a brush cutter, two stroke lawnmower, leaf blower wil it work?
as mechanical things is easy but electronic things im not the brightest crayon in the boxs
Just for the challenge my lower end is from a old kx 125 1985 thats is my base that im working from all the other stuff is missing... 😜
I would love to answer properly that question but I included would have to make some digging prior about the matter 😛
@@StepstoPodium awesome thank you keep the informative content coming we all learning here 👌
I sure will!! 🙌🙌🙌💪💪💪
A DTR 125 e a TZR usavam uma valvula controlada por um motor electrico
Brilliant..
My friend passed away when this velve open on kawasaki 150 ss , gas cable stuck and cant go back at 140 km / hour and more faster and faster , its happen quick no time to react or thinking , so first instinc was push back brake and lose ballance then he fell off
Sorry to hear that Sheldon 🙏
I enjoyed your governer joke, good vidio thanks for the explenation.
Thank you 🙂🙌
I believe it has more to do with port timing than port size
Anyone else think he sounds like borat? Good video by the way.
🙄😂
Thanks!!
How to set squares for Hero Hunda
brilliant!
Thank you SteveH! 🙌👌😄
Com os preços da gasolina, se também tivesse mos de alimentar um doente pqp! Qualidade sempre #1!
🤣🤣🤣🤣🤣🤣
In Yamaha we Trust 🙏!
What difference between power valve and reed valve
Power valve is an exhaust tuning technology. Reed valve is a 1 way check valve to allow fuel into the engine from the carburetor.
Yamaha TZM-150 legendary YPVS
you are like ibrahimovic
Like a Vtec , interesting
I've heard mechanics suggesting to just keep the powervalve open at all times by thread locking the mechanism and removing some parts. Do you think it's a good idea?
Nop 😂 why would you do this?
Now I know Centrifugal force are so useful in 11th I thought that why it's useful 😂
Your videos are great. This is almost like steam engine technology balls out
Thank you!! It's really simple, yeah :)
Show ✌🏾
🙌🙌🙌💪😊
Soo' thats! Power valve aaa litle Bit Like the secound caburator by the exoud- oud Port.
The only reason 2strokes are gutless at low rpm is they're purposely deprived of air flow.. That's all the ''power band'' is doing it just lets the engine actually take a gulp of air .
The power valve is about timing, not the size of the exhaust port.
The size determines timing
@@StepstoPodium Not size, but location. more precisely - the location of the upper edge of the exhaust window - the angle of its opening. this is what ypvs regulates. True, this is already boring on my part, but in the past, such an explanation, your explanation, misinformed me for years.
@@StepstoPodium для будущих поколений оставлю объяснение от Yamaha технологии ypvs: ruclips.net/video/4kERsqKC9Q4/видео.html
Thank you to Yamaha.
Resonance
Understanding how it works wasn't a complete mystery for me but boy can I get inside there for spring tuning ☹ that's a no no
It depends which bike you're tuning, but there are bikes that do not allow any adjustability 😛
@@StepstoPodium yz 125 1992
i still say it's black magic vodoo withcraftery is how the power valve works.😅.lol.
Hopefully after the video it's just black magic voodoo 😂
First off, I politely disagree. The port timing, the holes in the cylinder, a- "PRE PROGRAMMED PERFORMANCE CURVE, Is what controls it. The piston only ENABLES this performance curve. Proof?
CHANGE THE PISTON ALL YOU WANT- won't change by much. Change toe port size and timing in the cylinder- and your world changes!
It's definitely not a turbo, but it feels like one 😅
Agree!!
@StepstoPodium was on a YZ85, and I was very impressed at how quick it was and the fact it would destroy my crf250x