Power-difference between 2T 250cc engines/generations?

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11/17/2020 7:04 AM

I’m curios how much difference there is between, say, an YZ250-96 (”SuperEvo”) engine, a -02 and the -05 (I’ve owned a -06 myself, and feelt it hit to hard for my fast novice/slow intermediate, 48yr old, 155lbs featerwheight)?

The same goes for the 2001-2008 RM250’s, any differences in HP and ”rideability”?

I never tried a heavier flywheel on the -06, does it really tame it down that much?

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I had an -89 ”Evo-prepped” YZ250 this summer, with a ported cylinder, VForce3 and PC-system and loved the engine! Just the right amount of power and low end-grunt so I could ride long motos (and still be ”aggressive”), but still way more exciting engine-character than my sons FC250-19.

Sure, the brakes weren’t the best and the suspension weren’t always up to par (depending on the track), but still ALOT of fun!

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So I would love to build me a bit more modern 250 twostroke, and that’s why I’m hoping some of you guys could help me out here.

Sure, the easiest would be an 06< YZ250 again, with the KYB SSS-suspension, but as I said, get tired to fast with that engine-character.

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11/17/2020 7:10 AM
Edited Date/Time: 11/17/2020 7:14 AM

i think the modern yz250 engine is just short of 50 hp out of the box and i believe the older 250 2-stroke motors from the mid 90s were in the mid 40s. the old rm250s made like 41 hp but the last generation motor which is a yz clone is around 50 and its alot more aggressive than the yz motor.

its alot easier to take away HP than it is to add it..you can use a flywheel weight or gear it up or run it alittle on the rich side to mellow it out.

i had a 01 cr250 with an FMF pipe/powercore II silencer..that bike was pretty fast stock but if i jetted it just right it was literally too much for me at the time..a 17 yr old 120 lb kid. i ran it alittle rich just to mellow out the hit

my 04 cr250 was one of the most rideable bikes ive owned/ridden as it was very linear and didnt have the normal grunt of a 250 2-stroke..it was more like a big 125

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11/17/2020 7:15 AM

A late gen stock KTM 250 2T makes 50HP which is about 5 more HP than Japanese 2 strokes. Modifying the older bikes will never be as good as a newer model, the manufactures have done very well improving the bikes over the years.

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11/17/2020 7:28 AM

I've spent some time on a fairly stock 2000 yz250 (had a pipe), and thyen like 500+ hours on an 06+ with a pipe.
Very similar engine character but I guess the 2000 was more mellow.

This 2000 had the newer SSS stuff as well, it was a sweet bike and I never felt like my 06+ was really any better.

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11/17/2020 7:39 AM

I have a '96 KX I bought new and had it ported by Mitch Payton back then. It gives up nothing to a new KTM. In fact it was stronger on top but a bit less ride-able.

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11/17/2020 8:16 AM
Edited Date/Time: 11/17/2020 8:17 AM

To answer the OP's original question, the "02, '05 and '06 YZ250 engines are all the same. Yamaha hit upon a great powerplant in about '99 and re-tuned it one year, then left it alone. Only minor jetting changes and silencer lengths throughout the years, from what I remember.
The trend has been toward smoother power all these years, so older versions will likely hit harder ('98 and previous, although I've never ridden one of those.) Late '80s and early '90s bikes probably have even more hit but less power.
EDIT: PS, yes a flywheel weight will tame the power considerably. It would help you to not light up the rear tire as quickly.

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Braaapin' aint easy.

11/17/2020 8:17 AM

The mid-2000 Japanese bikes were just under 50 hp and quite fast. I had a 2000 CR 250, which was considered one of the faster 250s at the time. It was fast with nice, even power. I replaced it with a 2005 CR250 which was faster, but with less low end, but more mid and up power. I still have the '05 and ride it regularly. Both the mid-2000 YZs and CRs will ping on pump fuel and need either a mix of race fuel or head work to eliminate the detonation. Yamaha and Honda were stretching these production bikes to their limits (and slightly beyond) on pump fuel. But they made a lot of power.

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11/17/2020 10:40 AM

I can speak to my Suzuki experience. I bought a dozen new RM250s, the first in 88 and the last in 2002. Had a couple 40+ D14 championships on the 96/97 conventional fork models then retired from racing. Still always rode at my home track. Thought my last new one (2002) was super easy to ride. Went RMZ 250 in 07. Fast forward twelve years, missed the jap snap, found the nicest last model RM I could find, a low hour vet woods rider owned never raced 07 and I'm 64 years old. The 07 RM power seems so violent I suck on it. I'm way faster on my 07 now 290 RMZ. The RM looks really cool sitting in my shop and my new 2020 RMZ 250 is being delivered tomorrow.

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11/17/2020 11:29 AM

I Vintage race an 82 RM250Z and its reputation as a legendary 250 motor holds true. For an non-power valved motor it is a ripper and not far off my 06 RM250 through the upper midrange.
I recently bought an 03 Honda CR250R and it is more powerful than both of those previously mentioned bikes.
I also recently rode a 20 YZ 250 and was disappointed with the motor. My 03 CR is stronger mid to top, closer to new KTM power.
Lastly, I rode a 20 KTM and man that thing had a great motor. It is the best of the bunch..
I have not dyno'd any of them but that's my seat of the pants comparison for what its worth.

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Name withheld... Esquire


11/17/2020 12:15 PM

I can't comment on the older bikes but I had a 2007 RM250 that was quite aggressive when stock. I put a pro circuit pipe and muffler on it and that made it easier to ride. The hit was smoother and then it pulled better up top.
The smoothest setup I've had was a YZ250 with DEP pipe with standard length DEP silencer and a 9oz flywheel weight. There was almost no hit compared to stock and it pulled forever. On really slick tracks an 11oz flywheel weight would probably have been even better.
I now have a YZ250 with HGS exhaust and HGS shorty silencer and no flywheel weight. It hits hard but signs off earlier. I find I can short shift this set up though as it has more torque to pull the higher gears

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11/17/2020 12:55 PM

Donkey Kong wrote:

A late gen stock KTM 250 2T makes 50HP which is about 5 more HP than Japanese 2 strokes. Modifying the older bikes will never be as good as a newer model, the manufactures have done very well improving the bikes over the years.

Per the MXA dyno the '17+ KTM makes just over 47 stock. With a PC pipe and silencer it makes 49. Personal experience on the dyno with the PC combo and u4.4 51.5hp. The previous gen ('16 and older) were making 50 stock.

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2018 KTM 250sx
Instagram CamaroAJ

11/17/2020 3:50 PM

A Suzuki is a bit snappy compared to the yz but in a good way.
The yz hits harder and rips more on top. The Suzuki is quicker to turn over. Stock for stock.

I had a 2019 Ktm 250 and it didn’t have the immediate snappy throttle response of my Rm.
It had good smooth bottom and mid and fell on its face on top.
In my opinion all the last gen Japanese 250s run better and are more rider friendly. Just my opinion though.

Sounds like you may want a yz250x. I think that would be a very smooth engine.

Pictures for proof of opinion. Lol

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11/17/2020 4:50 PM

I had an 05 YZ. Loved the power on it. It was completely rebuilt with all OEM parts. No porting or anything. That bike was great! I have a 98 as well. Biggest difference I noticed was the 05 had more bottom and not quite as much on top as the 98. The 98 doesn't have much bottom compared to the 05, but it feels like it will pull forever. It's really fast up top! Not sure how it will transfer over to the track, but we will find out soon. The 05 was pure joy on the track.

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2017 RMZ450
2005 YZ250-sold :,(
1998 YZ250
2005 KX250F

80% of the time it works every time
IG @hammerfamily_4 & @2HRacing
Thanks to : Factory Effex, N2Dirt, Acerbis, DT1, Fasthouse, Matix, FMF, ASV, 100% & Mika Metals

11/17/2020 5:18 PM

JWACK wrote:

A Suzuki is a bit snappy compared to the yz but in a good way.
The yz hits harder and rips more on top. The Suzuki is quicker to turn over. Stock for stock.

I had a 2019 Ktm 250 and it didn’t have the immediate snappy throttle response of my Rm.
It had good smooth bottom and mid and fell on its face on top.
In my opinion all the last gen Japanese 250s run better and are more rider friendly. Just my opinion though.

Sounds like you may want a yz250x. I think that would be a very smooth engine.

Pictures for proof of opinion. Lol

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How was the KTM in the handling/suspension department? I had an 05 RM that I really enjoyed. That engine was very lively. Recently scored an 03 CR that I’ve never ridden yet. Needs a good amount of cash to get it race ready. Debating on pursuing a 17+ KTM.

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11/17/2020 5:32 PM

I prefer the RM in every way.
But you have to get the setup right or it can be a handful. Recently at Glen Helen the rm just wanted to kill me the entire time. By the time I got a decent setup the weekend was over. But that was my fault and not the bike really.
Keep the CR.

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11/17/2020 8:09 PM

As someone else mentioned the YZ250x has a smoother less violent delivery than a regular YZ. I also had an 06 YZ and at 150lbs I thought the power was a bit too aggressive. I rode a new YZX and really liked the engine character.

As you mentioned with the old school bikes the engines can be made to run quite well, it's the suspension, brakes, and ergos that hold the bike back.

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11/17/2020 8:32 PM

vtec wrote:

i think the modern yz250 engine is just short of 50 hp out of the box and i believe the older 250 2-stroke motors from the mid 90s were in the mid 40s. the old rm250s made like 41 hp but the last generation motor which is a yz clone is around 50 and its alot more aggressive than the yz motor.

its alot easier to take away HP than it is to add it..you can use a flywheel weight or gear it up or run it alittle on the rich side to mellow it out.

i had a 01 cr250 with an FMF pipe/powercore II silencer..that bike was pretty fast stock but if i jetted it just right it was literally too much for me at the time..a 17 yr old 120 lb kid. i ran it alittle rich just to mellow out the hit

my 04 cr250 was one of the most rideable bikes ive owned/ridden as it was very linear and didnt have the normal grunt of a 250 2-stroke..it was more like a big 125

Interesting you never here anything about a 04 cr250, sounds like a bike I would like. Power band similar to a 125 ? Mid to top ? I rode my pals 97 or 98 rm250, he had every bolt on, including a ignition. Ride it like your supposed to ride a 250 and it,s slow. So I ride it like a 125, screaming it, and slamming gears. I bought a 98 yz250 new, power was decent. Twisted the forks in the triple clamps, all the time, even with applied tclamp. Front end felt real light, odd. Restored a 90 cr250, pc, fmf pipe, answer silencer, smooth lowend theN just kept pulling, fun ice bike.

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11/18/2020 9:16 AM
Edited Date/Time: 11/18/2020 9:19 AM

My '07 KX250 has the hardest hitting most violent powerband of any 250 2t I've ridden. I'm a vet rider and owned/ridden/raced a bunch of 250s over the years.

Kawasaki designed the '05-07 engines for Bubba to be able to compete against the 450s at the time. I had a custom head insert made by Phathead, and threw on a 11oz flywheel weight to tame the power a bit. It's perfect for me now, it was almost unrideable when I got it.

Rode a brand new '16 YZ250 smoker and couldn't believe how mellow the powerband was.

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Ride like a girl!!!
2016 KTM 500 EXC-F
Current project: 2007 Kawasaki KX250-R7 retro build
Current project #2: 1987 Kawasaki KX250-E1 rider/racer resto
1989 KX125 resto
1987 RM250 resto

11/18/2020 9:21 AM

^Interesting queen of spodes. I had an 05 KX and then switched to an 09 YZ. For me, the powerplants were pretty similar.

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11/18/2020 9:33 AM

b_kowalsk wrote:

As someone else mentioned the YZ250x has a smoother less violent delivery than a regular YZ. I also had an 06 YZ and at 150lbs I thought the power was a bit too aggressive. I rode a new YZX and really liked the engine character.

As you mentioned with the old school bikes the engines can be made to run quite well, it's the suspension, brakes, and ergos that hold the bike back.

Same weight and on my 6th yz 250 i felt the same when i rode a 250x it was great

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11/18/2020 9:43 AM

seth505 wrote:

^Interesting queen of spodes. I had an 05 KX and then switched to an 09 YZ. For me, the powerplants were pretty similar.

Mine had a fully rebuilt engine with new OEM Kaw crank assembly, piston, conn rod, clutch, every bearing replaced and new centercases and engine covers. Could be the 05 you had was tired.

The magazines also criticized the '07 KX250 for having a violent powerband (and shit forks but that's separate)

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Ride like a girl!!!
2016 KTM 500 EXC-F
Current project: 2007 Kawasaki KX250-R7 retro build
Current project #2: 1987 Kawasaki KX250-E1 rider/racer resto
1989 KX125 resto
1987 RM250 resto

11/18/2020 11:05 AM

My 86 and 88 cr250s had sweet smooth power
Bands. At least thats how I remember them.

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11/18/2020 11:10 AM

I had an 05 250sx and I seem to remember a lot of hype about the engine being stronger than others in the class. It sure was a lot to hang onto.

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11/18/2020 11:30 AM
Edited Date/Time: 11/18/2020 11:32 AM

Donkey Kong wrote:

A late gen stock KTM 250 2T makes 50HP which is about 5 more HP than Japanese 2 strokes. Modifying the older bikes will never be as good as a newer model, the manufactures have done very well improving the bikes over the years.

That is... Completely wrong.

Peak numbers aside (which are close btw), the KTMs make all their power through the mid range, making something like 3.5-4hp more over the YZ250 in that area. The YZs make that same amount more than the KTM in the top end.

The YZ power is broader and easier to ride imo, though that is subjective. I've yet to meet anyone who has ridden both that prefers the KTM power, but that doesn't necessarily mean anything. The power valve is easily tunable on the KTM, which is a big plus.

The KTM is more advanced in other areas (chassis/geometry).

As an aside, I'm not sure that either the KTM or YZ engines can be modded enough to make more hp than a well tuned last gen CR250 engine. That case reed design was a monster. It had its own flaws though.

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James

11/18/2020 11:39 AM

b_kowalsk wrote:

As someone else mentioned the YZ250x has a smoother less violent delivery than a regular YZ. I also had an 06 YZ and at 150lbs I thought the power was a bit too aggressive. I rode a new YZX and really liked the engine character.

As you mentioned with the old school bikes the engines can be made to run quite well, it's the suspension, brakes, and ergos that hold the bike back.

The X with the power valve mod is probably as good as it gets for a 250 2 stroke for most mortals. Stock, I found it a little too tame and really difficult to get it to rev out, even with perfect jetting. That pv mod really helps open it up without making it hit as hard as the regular YZ.

I've done quite a bit of experimentation between X and regular YZ engine parts in general over the past few years and have a hybrid of sorts that runs beautifully for my needs/skill level. It's nice having all the options for parts between both bikes.

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James

11/18/2020 4:38 PM

I just rode my 96 cr 250 the other day and that motor may be one of the best out there ever for me......I'd certainly take that one over any of the newer generation honda's........ Loved those 90's cr 250....

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11/18/2020 9:26 PM
Edited Date/Time: 11/18/2020 9:27 PM

b_kowalsk wrote:

As someone else mentioned the YZ250x has a smoother less violent delivery than a regular YZ. I also had an 06 YZ and at 150lbs I thought the power was a bit too aggressive. I rode a new YZX and really liked the engine character.

As you mentioned with the old school bikes the engines can be made to run quite well, it's the suspension, brakes, and ergos that hold the bike back.

SoCalMX70 wrote:

The X with the power valve mod is probably as good as it gets for a 250 2 stroke for most mortals. Stock, I found it a little too tame and really difficult to get it to rev out, even with perfect jetting. That pv mod really helps open it up without making it hit as hard as the regular YZ.

I've done quite a bit of experimentation between X and regular YZ engine parts in general over the past few years and have a hybrid of sorts that runs beautifully for my needs/skill level. It's nice having all the options for parts between both bikes.

Please tell me more about those mods.

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11/18/2020 9:30 PM

250 cross wrote:

I can speak to my Suzuki experience. I bought a dozen new RM250s, the first in 88 and the last in 2002. Had a couple 40+ D14 championships on the 96/97 conventional fork models then retired from racing. Still always rode at my home track. Thought my last new one (2002) was super easy to ride. Went RMZ 250 in 07. Fast forward twelve years, missed the jap snap, found the nicest last model RM I could find, a low hour vet woods rider owned never raced 07 and I'm 64 years old. The 07 RM power seems so violent I suck on it. I'm way faster on my 07 now 290 RMZ. The RM looks really cool sitting in my shop and my new 2020 RMZ 250 is being delivered tomorrow.

Congrats on the new Rmz ! I really like my 2020 250rmz have about 30hrs since March Zero problems ! I just entered my first Mx Race at 66! Won first moto! I was the only yellow bike out of 16 seem like most of the old guys ride 450 husky or Ktm... Ok I was
Thinking of getting a 2T 125 /250 sounds like you have a bit of experience with both...
Thanks for your input!

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11/18/2020 10:02 PM

vtec wrote:

i think the modern yz250 engine is just short of 50 hp out of the box and i believe the older 250 2-stroke motors from the mid 90s were in the mid 40s. the old rm250s made like 41 hp but the last generation motor which is a yz clone is around 50 and its alot more aggressive than the yz motor.

its alot easier to take away HP than it is to add it..you can use a flywheel weight or gear it up or run it alittle on the rich side to mellow it out.

i had a 01 cr250 with an FMF pipe/powercore II silencer..that bike was pretty fast stock but if i jetted it just right it was literally too much for me at the time..a 17 yr old 120 lb kid. i ran it alittle rich just to mellow out the hit

my 04 cr250 was one of the most rideable bikes ive owned/ridden as it was very linear and didnt have the normal grunt of a 250 2-stroke..it was more like a big 125

profeshenal125 wrote:

Interesting you never here anything about a 04 cr250, sounds like a bike I would like. Power band similar to a 125 ? Mid to top ? I rode my pals 97 or 98 rm250, he had every bolt on, including a ignition. Ride it like your supposed to ride a 250 and it,s slow. So I ride it like a 125, screaming it, and slamming gears. I bought a 98 yz250 new, power was decent. Twisted the forks in the triple clamps, all the time, even with applied tclamp. Front end felt real light, odd. Restored a 90 cr250, pc, fmf pipe, answer silencer, smooth lowend theN just kept pulling, fun ice bike.

all the case reed cr250s are like big 125s..but supposedly the 05-07 were a bit better in that regard and with some massaging (milling down the head/squish band + airboot modification) they could be made into monsters. i personally liked it like this but if you are a bigger guy or like to lug your bikes i could see someone not liking it all that much.

i remember reading in mxa at the time that the 05-07 cr250 was a dyno monster due to its electronic powervalve system but in the real world it didnt stack up to the other bikes. the motor was based off a street bike motor and they never got it to its full potential due to the 4-stroke revolution that was occuring at the time.

my next bike (if i get back into riding) will probably be a yz250f but if i were to get another cr250 i would probably just get an 05 or newer and put on a lectron or pwk carb and a set of reeds and an exhaust system and call it a day.

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11/19/2020 9:26 AM

over the years i owned the following 250 bikes:

1992 cr 250: rocket fast, not tractable violent hit no mods.
1994 cr 250 not as exciting as the 92 more effective.
then went to 125s
2003 ktm sx 250 great engine attached to a shopping cart. nevr came to grips with the hydro clutch. put a stock exc silencer and heavier silencer made the engine super tractable.
went to 125s then 250 f and quit riding.
in 2015 restored a 2004 cr 250 with lowered cylinder and tightened squish. super powerful but turned over really quick. the gears were short.
2018 yz 250x felt slow after getting of the cr. after riding it along with my buddies i noticed it was deceitively fast. but smooth. it vibrates a bit, switched to pro taper evo with pillow top grips to calm down the vibes.

might get a brp top clamp or a mako 360 to further reduce handlebar vibration.

now i have in sight a sherco two stroke enduro.



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