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Old 05-31-2011, 07:07 PM   #1
zen rider OP
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Are 250-300cc the perfect size for a two stroke and why?

Do the 250-300 cc 2-strokes hit some sort of magic sweet spot with a fun swell of midrange and a true top-end hit that gets the adrenaline pumping more than other motors?

For some reason my 1990 CR250R 2-stroke ran better IMO than a CR500 that I rode. I'll never say the CR250 had more hp than CR500. But it was something about the 250 2 smoke's eagerness to rev and the strong mid-range that seemed to be a more fun, tractable bike. The 500 had low end but was abrupt, traction was poor, and it revved out too quick -- I thought. Granted, I often wondered if the 500 I sampled needed a re-build. So I've never known if my experience is representative? But from what I know the KX250 vs KX 500 and older YZ 250 vs YZ 490 followed a similar trend with bigger bores never catching on much outside of open desert type riding.

Similarly, I seem to see a trend with KTM wherein the 300 seems to have established itself as at least a contender as one of the best all around 2-stroke dirt bikes ever. In contrast the bigger KTM 380 2-stroke fell off in popularity. And the revvy, light 200 and strong KTM 250s remain popular.

Can someone please explain why the 250 2-strokes were faster on MX tracks than the (also) light 500s (most 500s were in the 235lb dry wt range)? Would a well set-up CR500 with suspension upgrades compete with a big-bore 4-stroke such as a KTM 530 or XR650R as an ultimate powerhouse dirt bike? Finally, did the manufacturers give up too soon on big bore 2-strokes or do the bigger bores have inherent limitations?
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zen rider screwed with this post 05-31-2011 at 07:11 PM Reason: typo
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Old 06-01-2011, 05:26 AM   #2
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Old 06-01-2011, 06:05 AM   #3
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First off let me say i had a 90 cr250 and I've kicked myself for saleing it ever since that bike was more fun then anything else i've ever owned. the only thing that can come close is my 660 Raptor, Honda perfected the 250 in 90-92 when they went to the aluminum frame it changed, they weren't as much fun anymore.

I own a 98 KTM200sxc now. and i've had 2000 200exc that i built with a mxc trans. (long story,) they are great bikes light and plenty of power for someone under 200lbs. I have a friend that has a 300exc. gobs of low end power.

now the 500 question. almost all 500s where over bored 250s. there frames where bigger and heavy. and when the 250s really became the MX champs the 500s just got pushed to the back burner. Most people that road them where in the desert where the massive power on top worked well and they could take reving like that for longer then a little 250.

The problem is that's not a big market as compared to MX. defentle not in the 90's. the 500s went for years with no changes. I think they only built them until they ran out of parts. (probably not but you know what I mean)

Now i have see a few of the CR500s converted to a newer CR250 frame and with some upgrades to the motor they are wicked. Heavy flywheel weights dual stage reads a good pipe and yeah that are mean.

as for the biger KTM 2 strokes I haven't got to ride one. 300 is as big as I've been on.

if you back serch the older Dirtrider mags and such of the late 90's you'll see the decline of the 500's and if you go back to the early 80's you'll see there peak.. maybe late 70's
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Old 06-01-2011, 07:15 AM   #4
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I'll go as far as to suggest that one 2-stroke in particular may be the best overall off road 2-stroke ever built...KTM300. I'm talking non-MX here. And no, I've never even owned a KTM, so no Koolaid drinker here. About a third of my riding buddies, and a good many of the riders I see all over Utah and Colorado ride these bikes. I've tried one, and it strikes me as the most 4-stroke'ish power delivery for a 2-stroke I can imagine...and I mean that in a good way. Lots of low end but enough power to scare you when necessary. Stick an electric starter on there like many have, and it may be the best off road 2-stroke ever. Opinions are like...well, you know the rest.
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Old 06-01-2011, 09:12 AM   #5
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A couple years ago Dirt Bike did an article about the KTM 300exc vs. 300mxc vs. KX250 with all the offroad mods and a 285 kit.

The last line of the very comprehensive article:
Quote:
"A KTM 300 is a KTM 300, and a KX 285 is not."
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Old 12-20-2011, 07:26 PM   #6
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How about 185s?

Or maybe even smaller such as 175 or 185 cc? The 250cc 2 strokes are certainly some great bikes. I think of the Yamaha DT at 250cc as the bike that started the whole ADV bike thing in a way. The name of the game with 2 cycles is light weight. The engines can be peaky and offer poor fuel economy compared to 4 cycles but they sure are light and simple. There are really small 2 cycle bikes at only 90 or 100cc, but these rarely have a full sized 21 inch front wheel and decent suspension travel. So this gives the Kawasaki KE175, Suzuki TS185, or the Yamaha DT175 as the lightest practical 2 stroke adventure bikes. Unfortunately these bikes have been gone from the USA for a long time. I may be mistaken, but I think that TS185s were still sold brand new in Mexico until 2003. There is always a desire for a little more power. Yamaha's DT230 Lanza is a bike I'd sure like to try. I agree that there is a sweet spot for 2 cycles between 175 and 300 cc. A 500 2 cycle can be a bit heavy and the fuel economy suffers so it gives up too many virtues for the extra power. Maybe 185 cc is perfect? Now where I can I find a nearly new TS185?
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Old 12-20-2011, 08:49 PM   #7
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Quote:
Originally Posted by RayAlazzurra View Post
Or maybe even smaller such as 175 or 185 cc? The 250cc 2 strokes are certainly some great bikes. I think of the Yamaha DT at 250cc as the bike that started the whole ADV bike thing in a way. The name of the game with 2 cycles is light weight. The engines can be peaky and offer poor fuel economy compared to 4 cycles but they sure are light and simple. There are really small 2 cycle bikes at only 90 or 100cc, but these rarely have a full sized 21 inch front wheel and decent suspension travel. So this gives the Kawasaki KE175, Suzuki TS185, or the Yamaha DT175 as the lightest practical 2 stroke adventure bikes. Unfortunately these bikes have been gone from the USA for a long time. I may be mistaken, but I think that TS185s were still sold brand new in Mexico until 2003. There is always a desire for a little more power. Yamaha's DT230 Lanza is a bike I'd sure like to try. I agree that there is a sweet spot for 2 cycles between 175 and 300 cc. A 500 2 cycle can be a bit heavy and the fuel economy suffers so it gives up too many virtues for the extra power. Maybe 185 cc is perfect? Now where I can I find a nearly new TS185?
Unfortunately you wont be able to find to many new 2 stroke bikes out there any more. Certainly none that can be plated, at least on the left coast.
However they do exist and the technology has kept pace with the 4 stroke bikes. Manufactures like Gas Gas, Husaberg, and KTM all make 2 stroke bikes in the 250 to 300 cc range. 5 or 6 speed, wide ratio transmissions, charging systems to run headlight/taillight/turn signals. Electric start, adjustable ignition mapping, fully adjustable exhaust port operation, (power valve), suspension to die for, and the price tag to match.
The 250 or more to point the 300 cc machines run more rotating weight in the engine. The displacement allows for excellent throttle response while still having the rotational weight for good torque characteristics.
The down side to these bikes is that with the performance come a maintenance price tag. Manufacture recommended engine tear downs at 80 hours. And I mean TEAR DOWN. Split the cases, check the big end bearing and everything in between. Piston/rings at a minimum at the 80 hour mark. These cylinders do not bore, you seize it up, it's off to have the cylinder bore re plated and sized.
My bad, I'm ranting. I love my 2 smoke, but as an enduro weapon. Dual sported? Naaah, I'd have to run crappy tires! LOL
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Old 12-20-2011, 08:50 PM   #8
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The reason 2 strokes are a dying breed here in the states are the emissions regulations applied to new vehicles of any type.the new version of a jap 175cc is basically the ktm 200 exc.havent rode 1.did about 30 miles on a borrowed ktm 300 xcw out in the cali desert and loved that bike .the ktm 300 has changable power valve springs with preload adjustment on each spring.the bike i rode felt like the throttle was connected to an electric motor-smooth and linear response.many third world countries still use 2 stroke bikes-i think thats what they use to get rid of old motor oil.in the late 80's i was into sand duning atv's.i had the last version of honda's 3 wheeler-the water cooled atc250r.i also had a fourtrax 250r with a cr500 motor stuffed in it.the cr500 seeemed to vibrate alot and had a mean hit-but didnt have a smooth over rev like the 250.in a long drag race the 500 would get about 6 bikes on the 250-but the 250 would reel it in at 75 or 80 mph.if i didnt need a plated dual sport bike i would own some kind of 300 ktm-the bike is very user freindly and the newer models have e-start.my brother had an old kawi kdx220 and wont part with it-its used in the woods on single track only.
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Old 12-20-2011, 08:56 PM   #9
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Old 12-20-2011, 09:04 PM   #10
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KTM snowmobiles?

"The down side to these bikes is that with the performance come a maintenance price tag. Manufacture recommended engine tear downs at 80 hours. And I mean TEAR DOWN. Split the cases, check the big end bearing and everything in between. Piston/rings at a minimum at the 80 hour mark. These cylinders do not bore, you seize it up, it's off to have the cylinder bore re plated and sized. "

I've heard about the KTM maintenance schedules and it makes me wonder... Do the snowmobile and PWC owners tear their 2 cycle sleds and ski doos down this often? I know that US Chrome and other places do a lot of business replating snowmobile cylinders with fresh Nicasil, but after how many engine hours of abuse? A lot of these sleds have power valves too. I guess the KTM engines are just designed for an extreme power to weight ratio and run a bit closer to the ragged edge. I also wonder how long the top end lasts on a newer 2 cycle like the Yamaha DT-230? They never sold in the USA so I do not know anyone who owns one. The old air cooled Yamaha DT 175s and DT 250s used to go quite a while and that was with pretty poor lubricants by today's standards.
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Old 12-20-2011, 09:22 PM   #11
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Quote:
Originally Posted by RayAlazzurra View Post
"The down side to these bikes is that with the performance come a maintenance price tag. Manufacture recommended engine tear downs at 80 hours. And I mean TEAR DOWN. Split the cases, check the big end bearing and everything in between. Piston/rings at a minimum at the 80 hour mark. These cylinders do not bore, you seize it up, it's off to have the cylinder bore re plated and sized. "

I've heard about the KTM maintenance schedules and it makes me wonder... Do the snowmobile and PWC owners tear their 2 cycle sleds and ski doos down this often? I know that US Chrome and other places do a lot of business replating snowmobile cylinders with fresh Nicasil, but after how many engine hours of abuse? A lot of these sleds have power valves too. I guess the KTM engines are just designed for an extreme power to weight ratio and run a bit closer to the ragged edge. I also wonder how long the top end lasts on a newer 2 cycle like the Yamaha DT-230? They never sold in the USA so I do not know anyone who owns one. The old air cooled Yamaha DT 175s and DT 250s used to go quite a while and that was with pretty poor lubricants by today's standards.
Good questions. I can't say about snowmobiles and PWCs. I figure the more competition orientated, the shorter the life cycle. I had Kawasaki triples in high school and and they were the sh!!t back then. Auto injection I think it was called, smoked like hell! My KTM runs Moterex full synthetic at 60:1 like the book says. A touch of smoke when cold, then nothing. I do my own maintenance (within reason) so I'm a freak for jetting. I HATE listening to the guys who roll their bikes off the trailer, kick it 20 or 30 kicks, then "pin" the throttle to clear the engine. Then have oil running out the front and back ends of their pipes after a 20 min ride.
Really I'm lying, I get a kick out of it. Makes the whole KTM mystique thing work!
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Old 08-06-2013, 11:19 PM   #12
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The reason 2 strokes are a dying breed here in the states are the emissions regulations applied to new vehicles of any type.
As long as it's being ridden off-road the EPA doesn't care. ONLY California State OHV parks care with their stupid Red/Green Sticker thing.

KTM sells a ton of 2 strokes. Yamaha still sells the YZ and I think some of the other guys are still making mini 2 strokes.

The emissions point is moot because Evinrude and SkiDoo have some really clean burning 2 strokes. I think the biggest demise of 2 strokes has been at the Pro level of racing all the top guys are on 4 strokes and now the AMA racing rules structure favors 4 strokes over 2 strokes.

It's all Yamaha's fault for putting the YZ400f into competition back in the late 90s. People laughed at Doug Henry 'til he finally won with that thing. <10 years later nobody was on 2strokes at the pro MX level.
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Old 08-07-2013, 05:26 AM   #13
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Originally Posted by RayAlazzurra View Post
...... I guess the KTM engines are just designed for an extreme power to weight ratio and run a bit closer to the ragged edge. I also wonder how long the top end lasts on a newer 2 cycle like the Yamaha DT-230? They never sold in the USA so I do not know anyone who owns one. The old air cooled Yamaha DT 175s and DT 250s used to go quite a while and that was with pretty poor lubricants by today's standards.
I rode a time capsule 1980'ish DT175 last fall. I can't believe it used to be my favorite bike back in the day. Back then it would smoke my KE175 and I lusted for one. But I was pretty shocked at the reality of how those old two strokes performed. It had a little power in a very limited rpm range but not much of anything anywhere else. It basically felt like a lawn mower engine.

The DT had no low end punch, no midrange punch and wouldn't rev out. It just chugged along with me holding the throttle WFO the whole time. The other surprising thing was it weighed more than my fully street legal MXC200. In comparison MXC has way more power everywhere, hits hard in the midrange and revs out into a strong top end. The DT had as much in common with my KTM as a Model A does with an Indy car.

In other words those old DT's, KE's, etc. lasted forever because they didn't make enough power to break anything. But that also made the old two stroke street legal "enduro" bikes more road friendly. I rode my KE125 everywhere because it was my only transportation for many years. They wouldn't seize bombing down the road all day with the throttle pinned and would happily chug away for years without service.

That said, my MXC is a 2001 and the cases have never been split. It just had the top end done and power valve serviced for $500 including shipping both ways. The cylinder was still perfect, crank seals good and the bottom end still tight. So running a KTM as a dual sport would seem to relieve some of the race bike maintenance pressure. But that hard midrange hit and shrieking top end that are so fun on a trail make it a handful on the highway.
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Old 08-07-2013, 05:49 AM   #14
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I rode a time capsule 1980'ish DT175 last fall...
IMO - That is mostly due to the restrictive pipe and muffler on the DT. Put a performance pipe on it, and it will be reasonably close to your current KTM - considering that it is 25cc's smaller, air cooled, and has no power valve.
The Yamaha IT-175/200's used basically the same motor, as did the Blaster ATV. A pipe and a reed cage really lets the motor run as designed.
IMO- 2-stroke technology really has not come very far since water cooling and variable height exhaust valves.
I would still like to find a nice DT-175 today, or a Can-Am TNT 175... Both were great bikes.

I feel that the 175/200cc class is the "Perfect size" for a 2-stroke motor. The 250's are pretty close, and the 300's are just too big, and vibrate too much.
125's are the most "FUN".
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Old 08-07-2013, 06:39 AM   #15
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Define "reasonably close".

The whole reason I was riding my buddy's DT-175 was because I felt the same way you just posted about them. He has a pair of them and I was planning to make him an offer for one. That is until I rode it and remembered what they are really like. This was a clean running example because a very good Yamaha mechanic has looked after them since new. Most of the DT-175's I rode never ran as well as these. But I was too disappointed to even consider owning one.
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