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331
Joined
5/19/2018
Location
La Plata, MD
US
Edited Date/Time
3/26/2020 6:46pm
Are they making similar HP these days? I think they are. Why not let the 250 2 stroke compete with them
The 250f also has a 3000-4000 LARGER window of usable power range and 5000-6000 higher rpm limit which helps with final drive gearing/mechanical advantage
In fact - in many recent tests of mine - the 250f's will out drag race a 250 two stroke japanese bike stock to stock.
The KTM 250sx being an exception to that - while MXA is reporting it maybe worse for 2019 - my dyno is reporting it to be stupidly strong and better than 18.
And my dyno also says opening the airbox slightly hurt HP - contrary to their reports but it does sound better (louder)
My dyno also said the PC pipe was the best bolt on I've ever tested power wise for any bike.
IT's time we had parity in racing 250cc PERIOD no strokes in the rule.
I truly believe the factory 250f's would eat the lunch of any 250 two stroke - which should be obvious when they are consistently as fast as the 450's in qualifying, and doing all the same rhythms weekly - and a 450 is 10 hp up from the good 250f's
The RPM range factory bikes run (16000) and power they make (50+) allow them to be really fast for a lot of reason a 250 two stroke would struggle to beat.
It's been allowed for years in Australia and it gives privateers a leg up to go racing with less expensive equipment. Sadly probably never happen in AMA but it should.
The Shop
By chance, ever dyno a Bill's Pipe on a 2-stroke?
Both bikes coming out a corner at the same time then a 250f will outrun a 250 smoker?? Then you have a dragrace. Not from standing still then i will flip backwards. Riding on a track not a dragstrip.
Well i have a the last cr250
Sorry to say but that is not gonna happen and i will tell you right away not even a 450 is going to do that. See it every week on the track and yes those riders are faster then me but coming together out of a corner at the same time a 250 4 stroke no matter what brand comes to short.. way to short for a overtake.
Fun part is that i am in second gear and those 250 350 and 450 in third gear. When they go to 4 gear i'm going to third.
Have friends what ride a 250 a 350 and a 450 and they all say the same.. we have to overtake you for the corner when you come out it's "bye bye"
Here are the 250 smokers allowed in the 250 4 stroke class. Only a smoker is harder to keep the pace up with the easy riding 4 strokes but for a amateur like me who rides for fun it's the best bike a cr250.
I don't think it's the AMA when dealing with AMA Outdoor Nationals, but rather MX Sports. See email below. Four-strokes are not better machines, they are just given a ridiculous double displacement advantage. The classes are STILL 125cc and 250cc, with a Supplemental Rule for Pro Racing that need reduced or removed.
Just because I know somebody will be crazy enough to enter a cr500 in the premier class... and I wanna see that.
any chance you can elaborate? did it change the curve or just give it more over-rev?
thanks for all insight.....
I am being 100% serious when I say I really don't understand why anyone likes thumpers. AT ALL.
Run what you brung, open class. Get rid of the lcqs to make room! Git on it, Feld!
For only a couple grand you can make the 2 stroke have 50hp vs about 9 grand for the 250f. These are both twisted development 50hp engines. It definitely lowers the cost barriers of entry. There is now no 2 stroke equivalent to the 450f since 250s are close in hp/weight to the 250f. These days a 125 is only a step up from a supermini between moving up to a 250f.
https://www.google.com/amp/s/motocrossactionmag.com/amp/bikes-yz250-two-stroke-vs-yz250f-four-stroke/
We are planning a segment of youtube videos showing some of the testing and daily grind around the shop.
In some of those segments will be some drag races - or more accurately put - roll races if you are into that world (im not)
We do all that sort of testing at various start rpms, gears, etc - to get a picture of what the bike is doing. In roll racing - any additional front side of the curve adds up HUGE in the race - so you must test at various points of the curve to get a fair picture of the power output. The dyno is the exact same thing - but more controlled environment with less variance and "subjective" data. But it's always fun to actually ride a bike over sit on it...and you can get a good picture for mapping oddities only via riding sometimes.
For instance - the 19 crf250 has moments in the curve it's class leading - but if you roll race only starting at under 100000 rpm it looses every race...and you'd never see the actual power output it has and would call it slow.
Then ride it on the track - and call it fast....because you keep it in the sweet spot more regularly.
If you don't own a dyno - but own two bikes and one is stock - one is mod - this sort of testing (with equal weight riders) done properly can tell you all you need to know about your mod.
Riding on the track IS a roll race - all the time. But the other factors that NO ONE SEEMS to understand is the riding ability and skills are MORE important that the power output.
1mph corner speed advantage is a 5-7 hp advantage taken out to a long straight away.. AKA if you had 5-7 less hp but 1mph more corner exit speed - you would "win" vs the slower rider.
As a second to that concept - if you gave me the "jump" in a roll race and i had a stock 125 - you had your 250 two stroke. It would take you nearly all of 3-5th gear to catch the 125. That .5-7 second "jump" is hard to overcome. this is why for TESTING purposes you and the other rider must be on the same page. It's not about WINNING to win - it's about fairly evaluating the two test bikes - and both riders getting on the gas at the same time - in teh same way - etc etc.
To do this - mostly 5th gear testing is required - as all modern bikes will wheelie easily or spin the tire under it.
Final gear ratio - is what determines acceleration rate. 250 two strokes are geared very "short". This allows them to accelerate closely to 450's who make 10hp more and far more torque. a 450 in 3rd gear will go about the same top speed a 250 will go in 5th - both at normal "gearing". But a 450 can practically never shift on the track - making it easy to ride and hard to out accelerate - shifts cost HUGE time.
250f's are geared even SHORTER than the 2 smoke. However their huge rpm window actually allows them more top speed than most 250 2 strokes while still having large mechanical advantage. That's why they turn fast laps.
The PC pipe added power just about everywhere. It didn't change curve shape just added to it - in a large amount.
I haven't tested the 19 bills pipe - it wasn't available at time of testing.
Pit Row
Had a former client who quit riding mention that to me - asking if kawasaki had a 250 for sale after he watched that commercial recently.
But I know we are the rare exception, I don’t understand how anyone feels or ride faster on those things, but I know for most people they are.
Check it out!
I believe the 250f was the fastest, lap times! that’s what he preferred
But a 250 2t is just more fun to ride
I say - sell that 07 with BNG and limited quantities - 100 a year tops. I'd bet they sell every one...
Power isn't everything - in fact is very little.
But mentally - KNOWING your down on power - is hard to swallow even if it's faster.
TC222 was probably the smartest of them all - with his custom yzf's and 350's. He KNEW the advantages.
The current ktm 450 is very much a RIDEABLE 450 - you can push it hard and rev it a lot like a 350 - it's smooth and manageable. I think his switch was based on the fact he got more r@d with the 450 and also wasn't asking for/making custom 1 off stuff that only he needed.
On top of that, 250cc 2 stroke shifter karts are getting 60s reliably. Hell, 125 shifter karts are routinely in the 45 range.
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