You are watching: How many horsepower is 250cc 4 stroke
Back in 2010, the MXA wrecking crew walk an apples-to-apples comparison in between the YZ250 two-stroke and also YZ250F four-stroke. No hop-ups, simply out-of-the-crate, bone-stock, head-to-head action. At the time, the YZ250 had currently been the same for half a decade. Nevertheless, the smoker winner by a landslide versus the thumper. Pound for pound, cc come cc, the two-stroke engine was superior. Well, that’s no 100-percent accurate. We turned our fastest lap times on the smoker, but we also turned our worst laps time on it. It can be faster, however it compelled lots of skill to be consistent. On the other hand, the YZ250F was like a bank clock—tick-tock, perfect lap times every time. The difficulty was that no one thought that the YZ250 two-stroke to be faster, other than for the committed old-schoolers.SINCE that is INTRODUCTION, THE YZ250F FOUR-STROKE has CONSTANTLY gained HORSEPOWER, while THE YZ250 TWO-STROKE HASBEEN stuck AT 46 because that YEARS.
For clarity’s sake, we need to go back in time to recognize what has happened in the two-versus-four rivalry. The straightforward YZ250 two-stroke has actually hung in at about 46 horsepower for numerous years, while the latest variation of the YZ250f is approximately 42 horsepower. It need to be provided that since its introduction, the YZ250F four-stroke has been constantly obtaining horsepower, if the YZ250 two-stroke has in stuck at 46 for years (with little to no hope of Yamaha giving it no longer juice).
What go this prove? that the time they room changin’. When two-strokes haven’t gotten a whole lot more powerful, 250 four-strokes keep getting much more pumped up v each pass year. By ours calculations, Yamaha has actually averaged a 5-horsepower increase every 7 years on the YZ250F. And also the 2017 KTM 250SXF is currently half-again as close come the YZ250 two-stroke; that is 44 horsepower isn’t that far from the YZ250 already.
Rather than wait for Yamaha to build a 46-horsepower YZ250F, we decided to take a fast shortcut via Jamie Ellis’ Twisted advance race shop. Jamie is what friend would contact a top-notch, first-class, grade-A, blue-chip, five-star, under-the-radar engine builder who has been affiliated in lot of AMA championships. Girlfriend won’t check out a Twisted advance logo ~ above the championship bikes the these big-name riders are riding. Jamie works as a consultant. He refuses to salary these teams for logo design placement. Heck, the doesn’t even give out free work to these top teams and also riders. Why? because they come to him. We already know that he can create a 49-horsepower YZ250F. Us know since we’ve experiment it.“IT i will not ~ BE A fair FIGHT. THE benefit WILL transition TO THE YZ250F IF YOU do THAT. YOU need A HOPPED-UP TWO-STROKE against A HOPPED-UP FOUR-STROKE TO gain THE price YOU are LOOKING FOR.” climate JAMIE SAID, “I’LL likewise MODIFY THE YZ250 TWO-STROKE.” WAIT, WHAT?
When us told Jamie about our idea of to run a hopped-up 250 four-stroke versus a share YZ250 two-stroke—because that would offer the 2 parity in horsepower—Jamie said, “It wouldn’t be a same fight. The benefit will change to the YZ250F if you perform that. You should compare a hopped-up two-stroke versus a hopped-up four-stroke to obtain the answer you are looking for.” then Jamie said, “I’ll likewise modify the YZ250 two-stroke.” Wait, what?
Jamie took a beat-up 2007 YZ250 two-stroke, i m sorry is basically the same as the 2020 YZ250, conserve for the plastics, and rebuilt the from scratch while adding his an enig sauce come the engine. The idea to be to hop-up the 2 bikes, YZ250 and YZ250F, to the exact same degree and see what happens. Allow the fight begin!
The Yamaha YZ250F Jamie constructed for us was the crème de la crème. No price was spared. It was made to go head come head against the manufacturing facility bikes on the Supercross circuit. Not possible? Jamie’s no worried. He to know top-level teams hold their engine development close to your chests. This is wherein Jamie has a niche market. He will offer anyone the best engine money can buy, simply as long as they have the right to front the cash. The comes with a steep price tag, however Twisted development has sufficient engines top top the AMA circuit the Jamie can back up his claims. The $7000 price tag because that the engine go not consisted of the $1000 Hinson clutch or $1050 FMF exhaust. When it come to structure top-notch thumpers, the is every in the parts. Jamie has actually his very own spec on the piston and cams. The crankshaft was rebuilt by Crank Works. The infection was sent for a treatment procedure to reduce friction, and the bearings were switched out for ceramic.
Probably the coolest attribute of the cycle is the dual-fuel injector device that Twisted advance borrowed native Kawasaki KX250F to use on various other brands. The 2nd injector is an installed upstream in the airbox. Jamie didn’t have luck v a second injector right off the bat, however he knew the theory had actually potential. So, the went out and bought more than 10 different injectors and also spent months testing them. Every injector had a various spray pattern—from sharp pin-like sprays come fine mist sprays. The move of the sprays varied from 35 to 45 degrees. Jamie found the potential the was trying to find with a 25-degree spray pattern. This patten to fill the velocity stack and tricked it into thinking the spray term was longer than it in reality was.
The 2nd injector is useless without the correct mapping. A Vortex ignition is provided in harmony through the dual-fuel injectors. The prior injector is programmed come come on in ~ 0- come 25-percent throttle. This injector handle the initial raw fuel to store the bike native bogging, coughing and stalling. After 25-percent throttle, over there is a linear transfer native the front injector to the rear injector, which at first kicks in in ~ 33-percent throttle. Calculation is based on throttle position and also rpm, therefore the engine can advantage from the enhanced upstream atomization. Bottom line: the life droplets that were being sprayed yes, really close come the accelerator body now end up being a fog that fuel, do the gas more volatile. The atomization of the second injector fills the chamber, do the fuel much easier to ignite.
TWISTED DEVELOPMENT’S YAMAHA YZ250 TWO-STROKE
For the MXA wrecking crew, this to be Rocky matches Ivan Drago everywhere again. A high-tech thumper against an old-dog smoker. The MXA check riders went the end on the YZ250 two-stroke first. Every rider had a blast. The strength was strong, playful and also easy to ride. The light engine braking the the smoker permitted the cycle to flow with ease roughly the track. It obtained over every the jumps through no trouble—although, as with any two-stroke, acquiring all the power to the ground can be difficult on certain species of dirt. In slick or hard-packed conditions, maintaining the behind tire under manage requires a deft hand. In deep loam or sand, check riders might just host the throttle wide open, dump the clutch and also power through without absent a beat.
When our test riders jumped ~ above the YZ250F, castle looked favor fish out of water. They were coming up quick on jumps, bogging the end of corners and absent their lines. All of them come in after ~ the first round proclaiming the smoker the unanimous winner. The thumper was explained as awkward and low on strength when contrasted to the snappy two-stroke.
We sent them back out on the YZ250 smoker because that a second time. Every test rider had actually the exact same feeling as before, but could sense places where the four-stroke was better. Again, adhering to the prescribed pattern, the test riders switched ago to the YZ250F four-stroke. We told the test riders come take your time getting used to the bikes after ~ the swaps. Castle switched earlier to the thumper and took some extra time ~ above it. Lap after lap, each driver looked an ext and much more comfortable. Every of them came in ~ the second round to proclaim the thumper the winner! everyone was laughing in ~ the perplexed results. Exactly how was the smoker, just minutes ago, light years far better than the thumper, and now it to be the other method around? They preserved going ago and forth till they can reach a hard conclusion.
The 2 engines can have the same optimal power, however the strength curves are human beings apart. The YZ250 two-stroke signs off 5000 rpm sooner 보다 the thumper. It has a power-now feeling. It access time hard, indications off fast and uses its explode of torque to shoot it the end of corners. You can be lazy or ride a equipment high without paying a penalty. It should be provided that if girlfriend raced a built-to-the-hilt YZ250F four-stroke the means you need to ride a YZ250 two-stroke, you will do auger a feet in the ground what on the an initial lap. The two-stroke to be go-for-broke, when the four-stroke required a much more calculated approach. It was tough for the check riders come switch perspectives as they switched bikes — but once they rode the thumper the means it needed to it is in ridden, they liked it. One forced you come unlock your mind and the other to clamp under on it.
The MXA testers were shifting the YZ250F four-stroke around 11 grand, due to the fact that it felt together if the strength leveled off, which, in a way, that did. So, they shifted early, thinking there was nothing left ~ above the table. Small did they understand that once they happen the 11 grand mark, the bike hit its afterburners. They were leaving much more than three ponies on the table. The burst of strength from 11,000 to 13,500 rpm was incredible—thanks to the 2nd injector. And also when change at height rpm, the bike would be right in the meat that its ideal power.
The test riders were enamored through the sheer power of the Twisted Development-built YZ250F. They had to shift up and rev the engine out until their eyes bled, which do the engine feel a lot choose a KTM 350SXF engine. When they learned come ride it where the strength was, the test riders began to get further over the jumps than on the smoker. In hard-packed conditions, the thumper tracked the ground like it had glue ~ above its tires, conversely, the smoker would shot to rest loose. As a bonus, you could be lazy and make failure on the four-stroke and the power would be right there at her fingertips. On the track, that was hard to feel the large difference in torque in between the two bikes. The included torque did do the smoker easier to ride, but it was still harder to ride 보다 the four-stroke.
Both of the Yamahas’ suspension components were reworked by Enzo. The thumper was equipped with A-Kit components. They both tackled incredibly far better than they walk in share trim, however the newer YZ250F chassis made every the difference in straight-line stability and also precision cornering. Ours testers preferred the narrow feel that the YZ250. Various other than that, the YZ250F thumper was superior in that is ergos.
THE SHOWDOWN TO finish ALL SHOWDOWNS
To it is in honest, it yes, really comes down to just how deep her pockets are. If you are in search of a close-to-50-horsepower racing engine, go through the YZ250 two-stroke. That is mechanically simple, cheap to repair, straightforward to hop-up and is competitive with top-dollar factory devices for a fraction of the price. That is good for the guy on a spending plan who desires to have actually fun and also be competitive in ~ the local level. The problem with the YZ250 is that it is built on one antiquated chassis. It’s not simply that YZ250 engine to be a decade old, however the framework geometry and also layout room also way past their primes. But, if price is a factor, the Yamaha YZ250 is her weapon that choice.THE YZ250F FOUR-STROKE TRIUMPHS end THE OLD SMOKER IN THE HANDLING, turning AND ERGONOMICS DEPARTMENTS. THOSE are THINGS the CAN’T BE fixed ON THE TWO-STOKE
The YZ250F four-stroke triumphs over the old smoker in the handling, turning and ergonomics departments. Those space things the can’t be addressed on the two-stoke. To reach the peak, Jamie’s duel-injection YZ250F engine is the answer. This bike is a powerhouse. That is downright superior what Jamie does the end of his small but mighty Twisted development shop. The $7000-dollar question is even if it is or no you have the right to afford it, add to the extr cost that the YZ250F, which will collection you ago a lot an ext than a provided YZ250 smoker—and become obsolete in rapid order. No racer would ever dream of purchase a supplied 10-year-old four-stroke.
But, friend came below to find out i m sorry is better—two or four? And, the prize is simple. If friend are right into the sports of motocross because that the fun of it, the YZ250 two-stroke wins hand down. That power delivery is exceptional. The thrill element is turn off the wall, and it it is intended maximum horsepower at a cost anyone deserve to afford. Because that pennies ~ above the dollar, you deserve to have the fastest bike in your course (and in amateur racing the YZ250 is legal to race versus YZ250Fs). What you conserve will keep you racing because that a whole year compared to the cost involved in four-stroke racing.IF you THINK YOU are ON THE quick TRACK to AMA nationwide STARDOM, YOU need to STAY far FROM THE YAMAHA YZ250 TWO-STROKE. That ISN’T WHAT THE manufacturing facility TEAMS RACE.
However, if friend think you space on the quick track to nationwide stardom, you should stay away from the Yamaha YZ250 two-stroke. The isn’t what the factory teams race—and for this reason anyone top top a smoker obviously no trying to admire the team scouts. Because all the “Big Four” offer 250 four-strokes, they won’t assist a racer ~ above a two-stroke. There is no upside to sponsoring riders ~ above two-strokes that will certainly make your four-strokes look at bad. So, if you desire a factory support ride, you need to race a four-stroke.
This shootout is no a tie; it’s simply not cut-and-dry. If every motocross racer had actually a 250 two-stroke choice that was status-backed, not sneered at, our sport would be healthier. Much more people could afford come ride, and also those who room riding now might afford to fix an engine failure for one-quarter the price of resolving a money-sucking four-banger. But, friend can’t take status, image and also self-worth out of the racing formula. Thus, the 250 four-stroke is the perfect machine for riders that are much less willing to risk their ego on an unpopular choice. The tie can’t be damaged by the MXA wrecking crew—only by the face in the mirror, money in the bank and need because that acceptance.
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For much more info or to order your own hopped-up 250cc Yamaha (two-or four-stroke),go to www.td-racing.com or speak to (951) 698-7222.