OzVMX Forum
Clubroom => Bike Talk => Topic started by: Graeme M on February 04, 2010, 12:28:50 pm
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Just reading the comparo in the latest Dirt Action of the 250Fs and the 150 2-strokes. I am curious about something. The 150s are almost as fast but lack in that they don't hook up as well, are 'busy' in the rear etc. They appear to develop about 2-4 HP less at the back wheel. The 250Fs are faster. However, a 250 2-stroke develops about 10 HP MORE than a 250F, yet the same applies. Too much power that is too skittery, so the average rider is a bit slower on the 2-stroke. Yet going back a few years people happily raced the 2-strokes and sought more power to be competitive. If you'd sold a 250 2-stroke that gave away 10 HP in favour of a broad enduro like power spread, you'd have been laughed out of the place. So, what gives?
Why all of a sudden are broad flat powerbands with low horsepower the hot setup? I'm talking 250s here cos I think the 450s are approaching the old 500s in terms of outright power.
What if someone built a 250cc 2T with say 35-38 HP (slightly more than a 4T) but a broad tractor like powerband combined with a 2-strokes quick response? Would that be competitive with a 250 4T? Or is it just that a 10,000rpm powerband will always be easier to ride than a 5,000rpm one?
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Hi Graeme, I know quite a few younger good riders that are choosing to go back to a 250 2 stroke after spending a few years compeditively racing 250 four strokes and stints on 450's. They like the extra torque of a good 250 2 stroke over the 250 four stroke and find them easier to ride than a 450. Who knows maybe we will have to dust off Cr500's and Kx500's again.
Regards Stan.
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After growing up on 2 strokes then a sabitical of almost 20 years and then jumping straight on a WR450F,
i reckon i have become a lazy rider and almost depending on the engine to get me out of trouble instead of thinking about getting out of trouble.....i was never a good rider but i am noticing that i am becoming bored with riding.
Jump on Thumpertalk.com and you will notice ALOT more people are asking about 2 stroke bike questions.
The ones that have jumped ship are having a ball again and are having to stay switched on and more alert.
Plus when things go bang on a 4banger.....they are not impressed with the rebuild costs.
I know its not a 250 Graeme,but it won't be long before i give the WR the flick.....the top heaviness and the fact that i ever hardly use that power in the bush makes me want to go back to the 250 2 smoke.
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a few years back when i was a bit poorer, i rode a white TTR250 Yammy evrywhere.
MX, trail rides and to and from work.
i never had the spark plug out of it and as you could imagine the valves were never shimmed either. just changed the oil and cleaned the filter and that was it.
i loved it!
on the MX track, it cornered beautifully and predictably and i found the corners were where i could make up ground.
after i sold it, i bought a 2000 model CR250 and phuck me!
what a weapon.
it took me ages to figure out how to ride it properly and i reckon i was slower on that than i was on my little TTR for a long time.
i grew to love the CR but the 250 2 bangers from where i stand command respect.
if your not fit or just after a lazy ride they can bite you big time.
now if i had my TTR donk in a YZ125 chassis... mmm, now that'd be a nice bike.
now in the vintage scene and the pre~75 125's are a ton of fun!
close to the ground if any trouble presents, so thats cool.
but i also like the bottom end grunt of my 360 2 banger as well.
not sure if this sheds any light on the topic, just raving on over 2 v's 4 i guess.
i liked my TTR.
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To ride a 2 stroke you need better throttle control. Then it all comes together. I raced a 250 4 stroke last year. This year I will race a 150 2 stroke. I will stay on 2 strokes for a while I think.
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I think a big part of it, is that we all run 2-strokes with too-light flywheel weights. Oh, the 'zing' feels great, but the reality is that its costing us traction and is increasing lap times.
And the fact that a 4T is basically a 'big bang' style of motor (to bastardise the Moto GP term), which is better at finding traction on dirt.
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Still it all depends what you like I had no trouble keeping with a new wr450f on my pe400 and the pe is so much more fun to ride when I finish my project one with the disc front end it will be just as good as a new bike. :)
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Graeme,
ADB have also done a similar test.
I think the reason a 2 t is more "Skittery" is that they are much lighter therefore tend to ride across the bumps, where a heavier 4t will ride through them.
As for the 2 t's being slower, I think that is just a case of test riders spending all their life on a 4t and not being able to ride a 2t properly.
I think if one of these test hot shots had the opportunity to spend 12 months on a 2t before these tests were carried out, the lap times might read a little different.
ADB also said MA is on the verge of allowing 250t's to compete in the lites class nation wide. (sorry not really vintage I know)
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yeah, I tend to that point of view. I can't see that the 4-stroke style of power is so much better that it makes up for a lot LESS power. Maybe it does, but if not, then you'd think that 15 years ago, building say a CR250 2T with an extra 15 lbs, 10 less HP and a broader powerband would have been a winner. But of course it wasn't. So, IF we could bring a gun 18 year old from 1995 into 2010 and put him on a YZ250 2T and let him race a gun 18 year old on a 250F, I wonder who'd win? Or even up against a 450F? Hmmm...
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It is the same as a 125GP is 1/7th the capacity of a MotoGP bike but is definantly isn't 7 times slower around the track.
Part of it is the traction a 4T gets from 1 power pulse every 720deg of crank rotation, where it's 2 power pulses in the same amount of crankshaft rotation from a 2T. So for the same rpm from the 2 engines (on a micro level) the 2T will have more tyre slippage than the 4T, although they both would appear to be spinning the rear.
I don't think less HP would be the go what would be a good idea and easy to try would be a flywheel weight on the 2T or better still a crankshaft with a higher inertia rating. As would some electronic control of the power valve.
EDIT
Ooops I glossed over Nathan's post ;D
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It's the 4 strokes power delivery and extra traction that makes them so good. A 250f has a lot more grunt out of corners than a 150 2t.
The 250 2 strokes power is snappy and more aggressive than a 250 4 stroke making it harder to ride even though it has more power it doesn't put it to the ground like a 4 stroke.
It's not the less power making them go faster.. it's the 4 stroke.
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imagine a 2t with traction control like the moto gp bikes have???
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A 250f has a lot more grunt out of corners than a 150 2t.
Because it has an extra 100cc.
It's not the less power making them go faster.. it's the 4 stroke.
No, It's because they are almost double the capacity of a 2t in the same class. This is the only way manufacturers where able to con the public that these were good bikes.
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Evo i was meaning less power comparing a 250f to a 250 2t.
The 4 stroke will run quicker lap times most of the time because of the easier to use power delivery and increased traction.
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what i have noticed riding my 500 2 smoker against
modern 4 bangers is corner speed
i dont know how many times i have stalled or nearly stalled
or nearly hit 4 strokes mid corner
i find on the 2 stroke you tend more too ride the whole corner
where the 4 strokes stop and go and point and shoot
took a helmet cam of a race and they seem to go like shit down the straights
brake early ride into corner square it and power out at a great rate of knots
where on a 2 stroke you brake later get on power early and hold it through turn
thats why i nearly hit them ::) no doubt they have great drive out of corners
i think this is the main differance :o
in the usa jason lawrence (tool) rode a new yz250 2 stroke
and then a 4 stroke and was 3 seconds faster on the 2 stroke
when i ride the new 4 strokes i find them boring cant wait too get back on my bike
must admit i liked the 2010 RM250F handled great and you could ride it like a 2 banger ;)
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what i have noticed riding my 500 2 smoker against
modern 4 bangers is corner speed
i dont know how many times i have stalled or nearly stalled
or nearly hit 4 strokes mid corner
i find on the 2 stroke you tend more too ride the whole corner
where the 4 strokes stop and go and point and shoot
took a helmet cam of a race and they seem to go like shit down the straights
brake early ride into corner square it and power out at a great rate of knots
where on a 2 stroke you brake later get on power early and hold it through turn
thats why i nearly hit them ::) no doubt they have great drive out of corners
There in lies the problem to pass you knock off your corner speed, then allowing a repass on the exit.Get up the inside and hold them out wide Rusty ;D A young fella at Kurri Kurri is flogging all the 250F's on a YZ 144 in Dirt Track gets holeshot and a 15m break at the first turn and they never catch him.
Frosty you can have traction control now if you want it.
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MXA did an article a year or so ago, where they had a few riders of differing ability compare a new CR450F to a 2001 CR500.
To cut a long story short, by the end of the testing they all wanted the CR500 engine in the CR450 frame. The ergonomics and suspension were the deciding factors in favour of the modern bike.
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There are plenty of 500 2 strokes getting around in alloy frames but no one is racing one competitively at a high level in motocross.
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Is there even a class to ride a 500 2-stroke in, at State/National level MX?
Traction control for a performance application on dirt is actually VERY difficult.
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Is there even a class to ride a 500 2-stroke in, at State/National level MX?
Good question.. Not sure on the rules these days.
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i would love to set my bike up for
a fast pro to ride i think he would be suprised ;D
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I think 500's are still too hard to ride. I would love to ride a 300 mxer. that might be the right amount of power. And a 200 for the lites then.
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what i have noticed riding my 500 2 smoker against
modern 4 bangers is corner speed
i dont know how many times i have stalled or nearly stalled
or nearly hit 4 strokes mid corner
i find on the 2 stroke you tend more too ride the whole corner
where the 4 strokes stop and go and point and shoot
Thats what i found playing on the MX track,my cornering is all f@#$ed up now,i would approach the corner at a certain speed thinking about holding a nice line around the corner but with all the engine braking of the 450 it would haul the bike up too quickly and the front diving make a mess of my cornering.With the added high weight of the 450,my 72 kg body trying to turn a 120kg pig aint fun....like holeshot said,i end up at almost a stop,then trying to gas it out.
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to ask a question - why does a 4T have more traction???? And Lozza - you say a 2T will have twice the tyre slippage because of 2 bangs per cycle but therefore won't it also have twice the drive per cycle???? I would of thought all of these would be due to amount of power being transferred to the ground - therefore 40 HP will slip x amount regardless of where from?
Now I know I aint right but why?
ta
Rossco
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Is there even a class to ride a 500 2-stroke in, at State/National level MX?
It would be the Open class (450F) as it stands wouldn't it?
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Is there even a class to ride a 500 2-stroke in, at State/National level MX?
Traction control for a performance application on dirt is actually VERY difficult.
The hardware is a cinch, determining the the exact amount of wheels spin would be the hard bit. If road racing is a guide most of the fast blokes use settings 2-3 out of 10.So I suppose dirt would be between that and zero.
A few years ago there was an outdoor meeting that developed a large bog hole, all the riders were nailing it full on with their thumb on the 'button' activting the second retarded advance curve as a cheap and cheerful traction control.
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imagine a 2t with traction control
Didn't the Yamaha DT230 have something like that? It also had electric start way before it appeared on the KTM EXC300 too.
Tex
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Opinions:A Good read:I know its not VMX ..but hey its Sunday ;D :P
Lightweight and ultra-responsive are great ways to describe the KTM 250 SX in the turns. It eats ruts for lunch.
It's been a while since I've ridden a two-stroke on a motocross track, and the KTM 250 SX definitely reminded me of how flat-out fast-and fun-these bikes are. Earlier in the day I'd been doing motos on 250Fs, and when I initially hopped on the two-stroke I proceeded to over-jump nearly every double and tabletop on the track. These things have power! In the KTM's case, the engine comes alive not with what I would describe as a hit but more with a surge; the low-to-mid-range delivery is incredibly strong but surprisingly useable. In fact, this RPM range was my favorite place to ride this bike, as venturing into the top end produces enough vibration to register on my internal Richter scale as "hazardous to dental work." Sure, you'll get this with any 250cc two-stroke, but why wring the bike out and rattle yourself to high heaven when you can just short-shift the bike and ride the useable wave of low-range meat? That's my thinking, anyway. Beyond the motor, this KTM feels extremely lightweight, yet it somehow still manages to get most of the power to the ground so long as you're in the ballpark of the right gear. It turns consistently well and handles chop decently, though I felt some kicking in the rear end that I couldn't quite adjust out with the rebound; I think I'm too light for the shock's spring rate. The fork springs were great for my weight but didn't quite work in sync with the rest of the motorcycle, causing the overall handling to suffer a tad. Nevertheless, I enjoyed playing around on this machine and came back to the truck with a huge (and, I'm happy to report, toothy) grin.
-Chris Denison/ 5'10"/ 155 lb/ Intermediate
If you want a bike that loves to have fun (in the air or on the ground) a 250 two-stroke is a solid choice. The 2010 KTM continually shows us why it's alive and well.
The simple fact about two-strokes is that they are making the same power as the four-strokes with half of the displacement. There is a disadvantage in the length of the power spread, with what seems about a little over half as long in the total length of RPM pulling time. Heck, two-strokes rarely rev over 10,000 RPM anyways. But there is a huge advantage in how light the bikes feel and how easy they are to throw around - thank the limited amount of centrifugal force spinning between your feet. And I can go on and on with comparisons and contrasts about which is better and which has advantages where. But in the current class structure, four-strokes have an advantage. So if you play by those rules, then the writing is on the wall. But if you live outside the constraints of some ridiculous class system and ride whatever you enjoy the most, then two-strokes make a lot of sense. Less maintenance, easier to service, less expensive, the list can go on. Though the choices are somewhat limited, KTM has continued to bring a first-class race ready bike to the table. I rode a '08 250SX for a whole year and only swapped it out for a 125SX in 2009. For 2010 the 250SX is as good as ever and one of the bikes I'd easily consider buying if I were more of a motocross racer. No, this wouldn't be the bike I'd be the fastest on or the one I'd win the most races on. But this two-stroke would be the bike I'd have the best balance with of being seriously competitive on (much more than on a 125) and having the maximum fun every time I rode.
Jimmy Lewis 5'10"/185 lb./Sr. Expert
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Sold the KTM250 and rode a Yam250F last year, now its for sale as i bought another 2 banger - YZ250 ( before they stop making them)
the 4 stroker seemed to be a plusher ride and you could do more laps untired, but i couldnt get my head around the cornering and the engine braking on ramps. I still cant get my head around i would have to ride up to 450 4t to race against a 250 2t - that tells you somthing about the power there.
Ziiingggggggggggggg zinng
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Good man Freaky. I gotta 2000 YZ 250 and they're the ducks nuts! You can buy all sorts of grouse trick stuff for the older ones (like mine) for peanuts.... ;)
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nimmo, i have already dinged the exhaust, been told its the same one from current back to 99 so thats a blessing, just have to hit ebay and see what turns up.
Did HAd a punch out on the new yam 450F - 2010 with the reverse barrel, bloody trick bit of gear, handles really really well, can see them hitting the pointy end. but that aside as an old fella in the end i cant justify the expense needed to run these new 4 bangers, i can run a 2ee all year and never open the oil filler if im tight, and know it wont be a problem.
NIMMO - CHOICE WAS EASY - reackon i've had every YZ250 from 95 ( or whatever the one was with the light purple frame - to 02 and they were prity much the same bike, never had one lunch and always 4 kicks tops.
The 4 banger liked to stall out and would leave you dry kicking for half a lap if it didnt like the way it felt.
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MA just had a rule change that now allows 250 2t's to race in the lites class in the MX Nationals, and word is that they extend this rule to state and local competition in 2011.
Finally a bit of parity in the classes.
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I raced a 2000 yz250 and a 2003 yzf250. What i notice, is when you nail the throttle out of a rough corner the 2 stroke rear end bucks and jumps around, whereas the 250 fourstroke is smoother. Also when nailing it hard towards a jump the fourstroke rear end drives smoother and straighter, which helps to pick your line. Also the hit of the 2 stroke is more physically draining. These traits make the fourstroke better for me as an older unfit mx'er.
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MA just had a rule change that now allows 250 2t's to race in the lites class in the MX Nationals, and word is that they extend this rule to state and local competition in 2011.
Finally a bit of parity in the classes.
Don't understand why they didn't make the rule across the lites class's and not just for Pro-lites. :-\
Affected Discipline: Motocross
Rule pertains to:
Classes of Competition
Current rule in 2010 Manual of Motorcycle Sport:
GCR 17.12.1
New rule after change:
GCR 17.12.1
Class Capacity 2-Stroke Capacity 4-Stroke
Pro Lites Up to 250cc 200cc-250cc
Rule suggested by: Motocross Commission
Rule adopted by: MA Board
Date rule change takes affect from: 18 February 2010
Feedback contact:
Ross Martin – MA, Manager – Commissions and Committees
(03) 9684 0504 or [email protected]
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The road racing Moriwaki MDH 250(CRF 250 in RS 125 frame) was allowed to go to 300cc to be competitive......................................with 2T 125's. Was only fast in qualifing for some strange reason and would finish at the back end of the top ten 25-35 seconds down
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The MDH 250 is about to become the Japanese standard as 2 stroke 125 and 250 racing stops. Like the NSR80 which was killed off in favour of the NSF100 even though the 80 is much faster the 100.
Expect and NSF250, then they will kill off the 2 strokes then sponsor an NSF series just to make sure the 4 strokes are the only ones out there.
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So does that mean the 2 stroke 250 this year we race agains the 250 four strokes ? in mX and Dt moderns
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So does that mean the 2 stroke 250 this year we race agains the 250 four strokes ? in mX and Dt moderns
17.12 is Championships--just the modern mx championships Freaksta 8)
cheers
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to make sure the 4 strokes are the only ones out there.
Tis the Honda way...............................
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Freaky the rule change is just for the MX nationals.....with a view to bring it in at state and local level next year.
Parity in the lites class (250 4t and 250 2t ) is being pushed hard in the US and on the surface that makes sense But , if this follows through to Australia, what do we do with the 125/150's ?
They would be pushed from the lites class, but there is no other class for them. They can't be rule out altogether as the are VITAL for young riders transitioning from the mini class. Do the clubs have to introduce another class to an already packed race day ?
Lozza your spot on, I recently saw a Honda promo video about their racing division. The Manager stated wthout a stutter that "Honda is not a car company or a motorcycle company, they are first and foremost a engine company and a fourstroke engine company at that"
If they had their way everyone would be on a fourstroke.......cause that's where the money is.
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This is from the US GNCC racing series on the weekend.....on the Can Am GNCC racing site
In the XC2 division, Jason "UK7" Thomas took advantage of the new rule, which allows 250 two-strokes to compete with 250 four-strokes in the Lites class this year, riding a Monster Energy/FAR Racing/ Andrews Cycles-backed YZ250 two-stroke to a first place finish in the division.
Last year's champ Factory FMF/KTM Off-Road's Kailub Russell went down in the first turn, but recovered to finish third, despite tearing the skin off his hand on the choppy course.
"I just washed out the front in the first turn, but going into the woods I was already in third, so I was pumped about that," said Russell. "The skin ripped on my hand and it was pretty bad after that.
Jesse Robinson, riding a two-stroke KTM, capitalized on Russell's injury to claim second.
"I was behind Thomas at the start but I kind of pumped up, and then Kailub caught me," said Robinson. "Later in the race, I just picked it up and moved into second."
Meanwhile, Kawasaki rider Josh Weisenfels and KTM-mounted Jake Korn rounded out the top five.
John Day grabbed the $100 Motorcycle-USA.com Holeshot Award at the start of the XC2 race.
Open A Rider Jordan Ashburn claimed the Top Amateur Award.
The second round of the Can-Am Grand National Cross Country series, The Maxxis General GNCC, is this weekend, March 6-7, in Washington Georgia.
About GNCC Racing
The Can-Am Grand National Cross Country Series is America's premier off-road racing series. Founded in 1979, the 13-round championship is produced exclusively by Racer Productions.ÊCross country racing is one of the most physically demanding sports in the world. The grueling three-hour GNCC races lead as many as 1,800 riders through tracks ranging in length from eight to 12 miles, competing for more than $3 million in prizes. With varied terrain, including hills, woods, mud, dirt, rocks and motocross sections, GNCC events are tests of both survival and speed. Weekly Television coverage begins each Sunday on Versus starting April 25. For more information, please visit www.gnccracing.com.
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You forgot to mention that Josh Strang from Inverell in Northern NSW won the event...... despite some of the "locals" atempts at cheating!!!!. The Seppos havent won their GNCC seris for quiet a while now...... Kiwis, Aussies and Euros giving them curry!!!... good to see.
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You forgot to mention that Josh Strang from Inverell in Northern NSW won the event...... despite some of the "locals" atempts at cheating!!!!. The Seppos havent won their GNCC seris for quiet a while now...... Kiwis, Aussies and Euros giving them curry!!!... good to see.
"I'm stoked to get the win and get off to a good start for once," said Strang, who has had bad luck at the Florida race in each of the last three years.
good old consistency while doing the yards on the Zuki :-* GO AUSSIE :P
cheers
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A hero of mine and KTM 2 stroke guru Harald Bartol is quoted in the latest AMCN as saying Dorna doesn't like two stroke because "They have the smell.............of poor people" ;D
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A hero of mine and KTM 2 stroke guru Harald Bartol is quoted in the latest AMCN as saying Dorna doesn't like two stroke because "They have the smell.............of poor people" ;D
That's ok then- cause we own both ,so we must be middle class ;) ;D
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A hero of mine and KTM 2 stroke guru Harald Bartol is quoted in the latest AMCN as saying Dorna doesn't like two stroke because "They have the smell.............of poor people" ;D
LOL....LOL That is classic gold!
Make a nice bumper sticker.
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Well you will love this monaro
RS125 v's SV650 (http://www.youtube.com/watch?v=Ps3pj2BgTjc)
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So the moral there is you need a 500% capacity advantage to outrun a RS125 in a straight line & holding a line is almost impoosible on a SV650 ;D
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So the moral there is you need a 500% capacity advantage to outrun a RS125 in a straight line & holding a line is almost impoosible on a SV650 ;D
;D ;D ;D