Inside a Pro Supercross and Motocross yz250 engine and cylinder.
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- Опубліковано 4 лип 2023
- Lets take a quick look inside Jared Lesher’s supercross main event engine and what he will be running some outdoors with.
We talk a little on porting and port comparison to a ktm, and discuss some goals with power and delivery. - Розваги
Very cool to see the subtle differences between the cylinders side by side and your HP-making methodology explained. Thank you for using Wiseco and we're stoked to support Jared!
Well done Wiseco for suporting these riders .Ill buy your products because of that 100%
Their cranks have/had a spotty reputation over the years. I saw a presser from Wiseco that they've been working on improving reliability of their cranks. Pretty sure Lesher wouldn't run something questionable in a race bike.
I have a 2019 YZ250 2-stroke with only about 15 hours on it, and I just took off the top end for a rebuild. Bike has stock chain and sprockets that are just starting to show some wear, (to get a better idea of how much use the bike does not have.), and the stock piston has damage it should not have. Yes, I do see a tiny bit of detonation damage (90 octane REC alky free gas is not enough octane for the stock bike), on the intake side of the head/cylinder interface, but the exhaust side has distorted ring grooves, (possibly not letting the rich machine warm up before riding, previous owner had about 4 hours on the machine.). Well, I have never seen a piston is such bad shape with so little time on it, and I expect my new Weisco forged piston to have much more life. As a degree earned quality control engineer myself, I can tell the quality of Yamaha has dropped considerably in the last 2 decades. Can you believe I had to dremel tool some material off the frame head stay area to get the head off, (not enough clearance, head studs possibly too long.). I thought getting the YZ that has not been changed much from 2005/6, would yield top notch quality. I was wrong.
KTM will always have my heart due to their commitment to the 2 stroke and its development.
No kick on two sroke is really really not the way to go.
It needs to come out of the boxe with a kickstarter even if there is electric starter.
I love my enduro ktm exc125 engine with no electricstart.
I will buy a bike with both but never will I buy a endurobike without kickstart!
I totally agree, although I did buy a brand new Enduro bike without a kickstart. It bothered me and still does but it was the bike I chose based on my needs. I do agree with you though… Every bike should have a kicker. 😢😢😡😡😂😂
How much do you want the EPA to force development and create costs high enough to damage market share? Not many people riding all these expensive bikes today. With out the 1986 production rule (that nobody in the USA really understands), and the EPA dictatorship forcing the 4-stroke engine on the industry, a new 25 2-stroke today would probably cost between 4-5 thousand dollars. There are land closures too, but that is the reason why bike sales used to be 10 times more than they are today, which is the least in history, especially given the higher population of today. I respect your decision to stay with a 2-stroke as I did with a YZ. But to be frank, nobody making a 2-stroke has really stuck to morality either. Yamaha over charges by about a grand of a new 250 2-stroke to help fund the 4-stroke forced development, and KTM is doing what the dictatorship says, knowing the dictatorship will end them eventually. I have a problem with the entire industry. It is not run by free people anymore. It is not free enterprise anymore.
250 2-stroke
Thanks for this Derek, this is the content people want. Pure race engines 250 two strokes.
I want to see the rod on a factory 250 and the gearbox.that one crankshaft looked like a stroker with the blueing by crankpin
@@bkh5746 Factory 250 fourstroke, or factory 250 two stroke?
Derek. You did a YZ 125 cylinder for me probably 12 years ago. Made me a 144 to your spec and it’s such a bulletproof motor. Thank you. Still run maxima castor oil at 20:1. Still going on the same piston. It’s a showpiece for me not a weekly ride. But I must say, you do flawless work and are a credit to your craft. Thanks again.
Dang 20:1 seems awful rich
@@Jakestarr172320:1 would be lean. More oil yes but less fuel. Rich or lean isn’t based off of the oil side of the ratio it’s based off of fuel. (Side note I also don’t agree with running 20:1 but if it’s working for him and making good power running it that fuel lean then I suppose it works lol)
rejet it for more fuel. I am suprised as well as 20:1 fuel / oil ratio as now almost everyone swears 50 or 60 :1 with these new super super synthetics . I have always run my 2 strokes 32:1 . As long as its jetted good and run on the pipe it will not carbon/ ash up . I even run all my 4 strokes 100:1 with a good synthetic oil and my engines love it.
@@Ry_Pox20:1 will always be considered too “rich” when talking 2 stroke, I see what you are saying but rich vs lean is not always referring to air to fuel ratio. In this case oil to gas ratio. Either way keep rippin 🤟🏻
20:1? I'm calling BS that's way too much oil.
Really enjoy theory talk from knowledgeable fellas like you. I dabble with some two stroke jet ski motors and have a entry level understanding. Major props to you. Thanks for sharing!
Great content on 2 strokes. The history and manufacturers comparisons, two thumbs up.
I always thought KTM’s made more power because of proper squish. Boy was I wrong.😂 Thanks for the vid and please post everything 2 stroke. It’s so interesting.
there is nothing more relaxing to me than building engines, its therapeutic how i get into my own lil world of peace. smoke alil Cannabis and i literally zone out tell I'm done. it's crazy the tunnel vision i get when I'm building an engine. i know the time it takes to film and edit a video, thank u.
I have watched countless hours of 2-stroke theory videos and got more out this short video than almost all of those. Great job of simplifying the major differences of a modified 2-stroke.
Powerseal Is Fkin Awesome! I sent them a destroyed cylinder with low expectations of them even considering working on it. Few weeks go by I get a billing statement and basically a brand new cylinder back. I cannot recommend them enough for cylinder work.
Man… I'm really glad that your advertisement popped up on my Instagram feed so I could immediately X it out and then come over to UA-cam like I always do when I'm interested in something. 😂😂😂 Super glad that I just found this channel right now this minute and I'm gonna be doing some binge watching..... yep. That's what I'm going to do!!!! New sub based on just this video alone… Literally. Excellent job. Thanks.
Awesome video. Thanks for sharing. Been rooting for jlesher.
Thank you,
Very informative.
I’m vintage, and still learning.
Brilliant video mate. More content like this would be great!
Liked and subscribed 🤙
👍Great explanation. I was picking up what you were putting down
Very cool , ive built a lot of ktm s for off with thin base gaskets and tighten up the squish band with SX heads and a little machine work. Sometimes ill blend the exhaust flange for better flow when the power valve is closed. I haven't really thought about the power valve cooling befor ,thanks.
Thanks for that--very informative. I port my own cylinders and am always looking for information, there is not much printed on the subject. You may know this, but in the 80s Yamaha had a power valve similar to the KTM. It had an hourglass design that changed the whole exhaust port, but I think it was on/off and not gradual.
On our Superkart yz 250 engines we made the sub exhaust port flow channels to the exhaust outlet more of a gentle blend to the point that the channels right to the exhaust stub , making the exhaust stub more of a T shape. This more of a roadrace Aprillia GP bike design . Doing this the helped the made the sub exhaust flows work better with the main exhaust flow. This gave us a nice boost on peak hp and really widened the power range on the over rev .
We have done fairly extensive modifications in this area in R&D. So far as welding the outside of the cylinder so we could grind it the way we really wanted. On our mx pipes it didn't do much. If we keep on this project for next year we might make some pipes.
@@HPRaceDevelopment Is the wiseco piston specifically tailored by wiseco to your bike or some other manufacturer's model? Or is that a big secret? Cheers :)
@@eamh2002 We used to sell a custom piston for these bikes years ago - then I found this one for a different bike that did the things we wanted. Saving clients money and allowing them to purchase a piston from any source is something we like to do - which isnt smart for business but i think is morally right
@@HPRaceDevelopment So which bike was the piston designed for? I'm building a yz for a mate.
@@craigdavies8099 wouldnt be useful for your build without the work we do in our port arrangement
Thanks for sharing, I learned a lot in 10 minutes.
Old Yamaha drum power valve was pretty linear bad thing was when it wore the stops out. You make great videos bro very informative. Don’t give away all your secrets.
Got to love the yz power valve.i customize my eye ports to open with the main exhaust port for maximum hit .thanks for the idea cheers.
I dont like that arrangment. less mid, no better peak for me
And, "back in the day" you had Yam, Hon-duh, Suzuki, Kawi.. And a "Bull Taco" (from my youngster years).. I'm happy to see KTM and a few others dug into the mix.. That club got stagnant for a while.. When the big brands (previously) had little slap boxing fights on tech leaps in HP (ETC), it was just.. well, playing games.. Now.. Even at my age now.. I am IMPRESSED..
Wow one of the best videos on here thanks for explaining
I opened the sub ports sooner and it seemed to make a good improvement for a local pro's outdoor motor.
Interesting to get the differences explained 👍🏻
Excited for the changes!
Very cool video dude!
This was awesome, thank you for this.
That "vapor" blasting is awesome for cleaning parts to look like new. That is one process In have never seen.
Man, you're a brilliant teacher! ;D
Priceless info, thank you
It’s Nice to hear experience 👍
Once it is done, run it on your dyno. Would love to see that powerband. Great video.
Dont have the bike here, but it's already been on the dyno before houston. Our yz250 dyno video is a similar result, jareds is a little better everywhere than the one we published
Wisco has always been my go to piston for rebuilds.. an a good porting an polishing always makes good horsepower, an matching your pipe an silencer, jetting and changing your power valve also make hp.. it just depends on what type of hp an how much hp you want.. an if you match everything you will make massive hp! So you can keep your secrets I already know them😂😂😂😂
MY engine mods for the YZ250 for more low end power. I will not be able to ride it until spring now, but this is what I am doing to it this winter. I will surly write about it after I ride it enough.
1) FMF Gnarly pipe for more low end power.
2) V-force reeds. The stock reed stop plate actually blocks off about 50% of the rear transfer reed port tunnel, and I will open the tunnel to that port window a bit.
3) Lower the cylinder by .024" by removing the cylinder base gasket and sealing the cylinder to the cases with a good gasket sealer, (I use 3M Nitrile rubber and gasket sealer #847 brown, and feed it though a medical syringe with a cut off needle for great bead control.). Your squish will then be about .050" or a tad less (plenty), but with the stock head, you will need about 100 octane fuel, (I will mix 110 with the 90 REC fuel to save money.). Lowering the cylinder will lower the exhaust port time area, in hopes to better match the FMF lower rpm pipe.
4) do a good job jetting the carb. There is probably more than 2hp right there for a stock bike. Mine is so rich, I can't believe I am not fouling plugs, how black, wet it is stock.
These simple and reversible mods should shift the power curve down for much more mid range and lower rpm power, and be a much better power delivery for anything but a modern MX track, (which I consider dirty road race courses today basically).
Great video, the KTM power valve does look far superior, how do Beta and Sherco power valves compare in their design?
I remember working on those rotary valves in the 1980's.
They were used on a bunch of street 125's and 250 twins.
That' seems a logical development by KTM, even if it took almost 40 years. (I haven't ridden a KTM since the 80's 300cc one)
The guillotine gate valve used to be progressive with a centrifugal governor although it took a bit of tuning to prevent it being on or off.
Much better design where it cant fall into cylinder when it breaks
I forget if it was Yamaha or Suzuki who went to servomotor control first way back when.
Yamaha main market was (is?) 'play bikers', sales were just not high enough to justify a complete redesign for the few hundred bikes they would sell every year to semi-professional racers
Any idea of why that little angled notch/ramp is machined into the KTM cylinder in the bottom edge of the cylinder skirt on the exhaust side?
Great content, subscribed for shore. Which Oil do you recomend for mix?? I would like the special smell of 2 Strocke racing oil!!?
You should do the same video comparing yz a yz 125 and 125 sx cylinder! Very cool to see the small differences. I have never rode a ktm 250 sx, but love my yz 250!
YZ125 and ktm 125 more different than the 250's are but still somewhat similar.
Does the 2022 yz125 still run a split main exhaust port?
@@bruce3725 The port still has a bridge in the middle.
@@bruce3725 Yep.
What gains are to be had these days on 2 strokes? Last motor i had ported was a 98 cr125 and it dynod at 37 hp. I thought it was fast lol
Hey, if you have access to a dyno, I have a port roof angle you might want to try. I do port and stroke little 30cc engines for a living, and the engines I work on actually have a negative roof angle on the front transfers (exhaust side). I don't remember the angle degree (under 10 degrees I am sure), but what they are doing is "bouncing" the charge off the piston crown for a more upward stream from the front transfers. The rear transfer roofs are flat. I can't get a YZ250 engine on my dyno. :)
Thanks for the info. I run old kdx and a wr450. The old 2t is nice but parts are limited.
If your KDX is a 250, regular KX250 parts of the same year will work.
I was told that every manufactuter had to have its own powervalve method as each was a propriorty owned patent and each company could not duplicate or even resemble any other. When the all came out each was truly unique. Yamaha on sleds using servo motor and cables seemed overkill ( but linear) and the Rotax with diaphram / guillotine the simpliest but effective and adjustability with preloading spring with rotating threaded disc on cover .
What’s the part number for the piston you run ??
Thank you thank you thank you!
I’m real curious how TM stacks up in this category being as small as they are, do they combine both methods of exhaust port design? Super cool, thanks for going deep in this one!
Also curious about the TM's ability to hang.
Can you compare the cylinder from the new yz125 engine wirh the ktm125??? Did Yamaha miss the mark getting ktm like 125 power on their new engine???
Have you (or will you) reveal what the two strike launch control was that you almost (or did) get set up before the end of the sx season?
have a look at a Yamaha TZ 250/TZ125 cyl ... mounting looks pretty close and it has a bunch more port ... though it is made for more peek HP at 12k rpm ish my TZ 250 (its a twin ) dyno'ed at 98 hp the 5KE models had a rotary power valve. might not work but just a thought. Cheers Bebop
Very cool to know!
This was so cool
Hi guys it's me again to let you know that one of my ideas (butterfly baffle in the exhaust for shorter tuned length) has been built and tested please search "Two Stroke 3,5 HP to 28 HP in 7 minutes". Bear in mind I and the builder had never had any conversation about the subject so I don't know how he had a similar idea.
How do they compare to the Sherco
Cool stuff man! Question, do you ever use different base gaskets thicknesses to play with the powerband? Ran an athena race gasket (thinner)on my last topend and seemed to give it more bottem end but less up top. Was great for tight tracks.
We do this through our port changes for the target goals. Changing gasket heights is noticeable but very small differences.
KTM has my heart because I can interchange so many parts. I can use an axle from a 2003 125 on 2018 690. Many more examples, but I love parts interchange.
Also notice on the KTM vs. YZ main exhaust port, the roof of the exhaust port on the KTM has a very large arc for a port roof, where the YZ is more flat. You are measuring the width of that KTM exhaust port at a very low spot, just above the transfers, (at the end of the "blow down phase". Have you actually measured the "port time area" of both to see the difference there? Because those shapes can be deceiving.
I hope the bearings hold up in that hot rod crank and main bearings
Wiseco, but we hope so too! It's been our experience the OEM bearings and parts are no longer the quality they used to be either...since covid a lot of things have changed.
KTM for the win!
You know your stuff!👍
Nice info 👍
Valve on KTM is similar to 96kx how it changes port timing
Ooooooookayyyy I’m subbing 😮💨😮💨😮💨🔥
To YZ 250 owners. I thought running 90 octane "REC fuel" (alky free), would be good enough octane for my stock YZ250 motor, (also knowing Yamaha reduced the compression ration a bit around 2011), but it was wasn't. I just took the top end apart and found a little bit of detonation damage on the intake side of the cylinder/head interface, (I can still use the cylinder thankfully, but am putting on a new head). What I thought was the sound of piston slap at very low rpms when I got on the gas, was probably the detonation that did this bit of damage. I have also never seen a stock piston as weak as the YZ250 stock piston, so get rid of that stock piston ASAP IMO. :)
Absolutely shocked to see a powervalve thats either open or closed when Yamaha were using powervalves that opened progressively in the 80s!
The power valve that KTM uses is exactly the same as the YPVS that Yamaha used in the 80's. Strange that Yamaha abandoned it and KTM copied it.
it abandoned that design cause there is no need to got a progressive port, reeds do the entire job@@jimduke3
It might be because I gained 20-30 lbs, but my 2019 YZ250 is probably the slowest 250cc MX bike I ever owned box stock. My stock 97 KX250 would eat it's lunch. This 2019 YZ runs a lot like my 1986 YZ250 did.
Good job
There is a progression with the YZ power valve. The main valve opens before the sub exhaust valves, and i bet, by the torque it takes to open the sub exhaust valves may take up to an extra 2000 rpm (I did not measure it), to start opening the sub exhaust port valves.
You can change the timing of the sub exhaust valves with a different ramps on the power valve shaft, that do open the sub exhaust valves later than the main valve.
Opps, I should listen the the entire vid before I open my mouth. :)
Thanks
Great video! Ok so the lower transfer ports you do not polish? I remember back in the day ok I know I’m ancient the factory bikes transfers and exhaust were polished to a mirror finish. They weren’t water cooled so is that why the cylinders aren’t polished?
I’m using what I learned in dirt bikes on chainsaws now and you can tell the difference!
Ive learned that polishing is only benificial for exhaust ports.
I am curious of what kind of fuel/oil and ratio Jared is running in this YZ250 for SX?
Jared is supported by bludlubricants, and best I remember he runs 32:1
My yamaha DT 125R has similar power valve to that ktm, with electronic controll and its an old early 90 model.
must be a ripper
Brilliant.
Do you have good experience with PowerSeal coating? I have send them several cylinders and the coating was not hard enough. Two stroke cylinders with only one ring worked for 10 hours of racing. 4 stroke cylinders with three ring applications didn't even survive the starting procedure. I checked ring gaps and everything was mounted correctly.
Sounds like a unique problem to you, we use them all the time and have hundreds of hours of success on their plating.
@HPRaceDevelopment thanks for your answer! I guess its working on Chromed Pistonrings and when it comes to four stroke pistons with sharp chastiron pistonrings, it doesn't match well with the plating material.
I tried 4 cylinders in total. Only one survived. Trying monardi Italy now.
BTW: thanks for your CDI and Ignition videos! This is how I came here :)
@@diesdasa we dont run chromed rings…
you probably have other issues
The comparison between the exhaustareatime from ktm and yamaha is not correct. If you have a wider Maine haustport, so you have smaller sideport. For yamaha the opposite. If each done correct, you have the same Exhausttimearea. The smaller mainexhaustport makes a longer pistonlife.
Late to the party. Just discovered your channel. How do the modern exhaust port and exhaust valve designs compare in power to say the ancient 1980s and '90s Kawasaki 2-strokes with the KIPS variable exhaust valve timing? Pretty sure Honda and Yamaha had variable exhaust valves too.
The designs improved from the 80s in many ways until last gen engines - this yz or the cr (nearly a ktm level design). The problem is - ktm has the best design by far at this point. The ktm has some flaws - the valve will collect more heat it cant shed than other concepts - but its function is unmatched.
Yamaha RZ350s in 1983 had a two stage servo motor controld pover valve opened at 6000rpm stage 1,then 8000rpm stage 2 with red line of 10000rpm.the bikes had very good mid range and top end for a 60hp twin 2t.
Is the cylinder liner made from cast iron?
no
My 1983 Yamaha RD 350 YPVS had the same valves like this KTM valves !
similae but not same
@@HPRaceDevelopment But the shape of the outlet is the same and the system had also an inbetween position, for more torque, at low engine speed!!
My question is why on the 22 yz125 they are using a tpms sensor?
To adjust the ignition map just like they do on the 250 based off TPS
Hey Derek, will Jared be using the new STIC Super X carb? I keep it under control with the slowest turn G2 throttle cam, for MX!. I immediately started mixing it up with faster riders at the track.
We haven't tested with it yet. We have been having some issues with junk getting into his carb/jets late in motos. Not sure why or how, we filter the fuel and have an inline filter. Hope to sort this out soon!
If the yz exhaust could be opimized with an electronic motor would it be a noticeable difference?
My guess it would because just snapping open is a harsh delivery.
No its a guillitine type valve
ktm uses one that is the roof - not blocking the roof with a void behind it like the yz
It could arguably be slightly better - but not ktm better
good question
@HPRaceDevelopment thanks for your response. Your time is appreciated
Wow didn't know that about the 250 ktms
Do you build these setups for other people as well or just this guy? I've been trying to dial in my yz125 for a little bit now and I'd like to do something similar to this
Full blown race shop that makes a living off selling what we race…If you want our best effort its just time and money
@@HPRaceDevelopment good to know, I'm a quality over quantity guy myself so I can appreciate that attitude. I'll be in touch, I'd like to get the most out of a stock bore setup to avoid the big bore headaches
The new STIC Super X carb on my stock 200SX...FIRE Derek is a dealer and BTW Lesher runs the STIC metering block version. Might be overkill, if you're only looking for a little more power.
Thank you for the info, less comp less cooling ,gee in a sand track 30 minute Moto ? The little extra cooling and less proned to detention
look what happened to Hunter today I know its a 4 stroke just saying. Reliable is key
We currently make most power at lowest compression setting on the yamaha of all the heads we tested. We will be testing the KTM head profile in the yamaha soon - see what happens.
Sucks for hunter - making this title hard for him!
What engine was that piston for? I just put one in my ktm 250 and it had 2 rings. That one only has one. Do you see any drawbacks with that?
Generally 1 ring makes a little more power. Arguments on both sides to benefits for each design.
if i had to guess, cr250 gp piston
@@warclownband Nope but good guess
@@warclownband Ahhh, the center of a tootsy pop conundrum. The world will never know what kind it is. lol
What's the best mod I can do for my 01 cr250 although it's plenty fast. Set squish? Send to you!?
Not many "bolt ons" will do much. Keeping the engine fresh, and your jetting on the money is the best thing anyone can do, mod or stock.
@@HPRaceDevelopment thank you!
Does a 2005 Yz 250 Zylinder fit on a 2023 yz 250 ?
It does
Generally speaking, do all (performance) 2 strokes benefit from a crank stuffer?
Not really.
@HPRaceDevelopment thanks for the reply. I have a twin 951 currently rebuilding and was looking at how big the crankcase is. It just got me thinking. Love the videos man! Thanks for posting and sharing knowledge.
We were stuffing cranks (just the holes) back in the 70's with Epoxy.
The KTM valve is much like the original YZ250 power valve from 1982.
As a privateer riding for fun what is your opinion about reliability of YZ/SX here? Thanks!
I think yamaha has fallen off a cliff over the years in part quality. But in general the yz is ok. Depends what your std is for acceptable rebuild time
@@HPRaceDevelopment Thank you.
Quality: have heard the same. Friend of mine riding Yamahas for years.
How is the wiseco crank working i have heard from several people that they are almost as bad as Chinese crap i almost bought one but decided to just have my old factory one rebuilt trued and balanced the wiseco pistons are great so I had a hard time believing their cranks but so many folks said it but some of those folks might not have been as ocd with rebuilding as i am and I make sure everything is where its supposed to be and everything is moving perfectly and everything is tight and to spec i have seen how some guys just throw everything back together without using a torque wrench and the correct presses and other tools so idk
The older generation cranks from them were terrible and chinese. This new generation looks totally different, has different materials, and rod, etc..and it has been good enough so far to qualify for ironman outdoor national, and win the pastrana pro challenge. So I would say thus far it has been great. We will be putting them to the test next year with ax and sx based off our current results with this one.
@@HPRaceDevelopment ok keep us updated
do you do repairs on cylinders or just the sweet sweet porting
Usually we don't repair anything - cheaper to buy a new one.
@HPRaceDevelopment idk if I can for this 2001 ktm 300 at the moment
If the yz is limited in rpm due to the exhaust port, just maximise it for lower rpm, raise the gearing. Are you always short 5hp against a ktm? You can't get that hp at a lower rpm with the yz?
improving torque requires more air trapt into the engine at any rpm
You cant just “add torque” by optimizing for “lower rpm”
We are already optimizing as much as possible. The optimizations are as I detailed. Aka ktm has advanced their tech and yamaha has not.
I gotta get my hands on a ktm
lol
Class with Professor Harris is in session y’all
Fitting a thick wall cylinder liner/sleeve would allow repositioning of the exhaust ports and maintain bridges for the rings. It also makes the barrel more serviceable and tuneable.
The YZ power valve needs a re-think straight up and would require a re-design due to reduced port timing and increased width when fitting a sleeve..
Bigger isn't always better is demonstrated with crank case and transfer volume differences between the two. Big = slow (low velocity) Small = fast.. Fuel requires velocity in order to stay in suspension. You can not burn what stays on the crankcase walls. More performance could be found through the entire range by reducing the YZ crankcase volume and and reducing the rate of area change.
Compression doesn't make power. Releasing the energy from the fuel uniformly and efficiently makes power. Hot spots are the enemy. High octane fuel is actually counter productive to making power. It does however make up for poor thermal efficiency design.
Steel sleeves loose significant power from plated cylinders - been there, tested that. Additionally the length of the divider of the aux port becomes prone to cracking is it shortens. The combustion forces are trying to stretch apart the cylinder and a large portion of that load goes through teh bridges.
@@HPRaceDevelopment Steel is rarely used for sleeves for a variety of reasons. I always thought the combustion forces were pushing the piston down to turn the crank...
@@jdoe9518 And equally pushing the head up as a reactionary force… it just doesnt moved
@@HPRaceDevelopment if you're doing it right peak cylinder pressure will occur 5 - 15 degrees after top dead centre. Because pushing the piston is more efficient than pushing the head
@@jdoe9518 I dont think you understand how pressure and forces work. The pressure at any piston position is inside the cylinder - always pushing the head away. this force is trying to lift the head and consequently cylinder away from the cases - at all times.
now i understand why it's harder to ride smooth with a yz250 because ofthe open/close position of the powervalve.
Only part of it. All 2 strokes have the pipe influence which has a dramatic rise in power as well - the pipe only resonates properly over a small rpm window - aka “getting on the pipe”
Do y'all have any thoughts on how/why the GasGas two stroke engines are so much more powerful than the Husqvarna and KTM engines even though they're coming out of the same factory in Mattighoffen, Austria
? The testers' shootouts have GasGas power and delivery rated top of the heap against all 7 of the other two strokes in 2023.
It has a carb vs efi. The efi just isnt there yet
the 24 gas gas will be in line with the 23 ktm and husky
New clutch, 20 starts, swap cylinder, new clutch, 20 starts to see best average elapsed time to the “first turn” and compare the cylinders. I chose the cylinder with the better over rev as it felt better on the track in practice, but as we know by the time the motos roll around the national tracks are so rough and rutted that the torquey cylinder may actually help a rider stay on top of things. Hindsight I wish I would’ve done the start comparisons and made my decision on cylinders based solely on that. Get out get clean.
When going against 450s with 8-12 nore hp and 3x the power width, on metal grates that take away rider skill, the start is a non factor. You just wont get a good one, period.
hello! nice video!
can you put a ktm cylinder on a yamaha engine?
Not legally for AMA racing
@@HPRaceDevelopment oh ok becouse i thougt that it would b e posible becouse same cc and if the ports just dont match you can just port the crank case.
thanks for the awnser!
@@hogsbyavgaming9965 - Also, the carb/reed block are mounted to the cylinder, on the Yam. On the KTM they are mounted the the crank cases, which would make it difficult