Post by: chump6784 on August 27, 2012, 11:57:19 AM
Ergonomics. Both bikes feel different but both are comfortable and I could switch between them between moto?s and I don?t think I would have a problem. The KTM is taller and wider around the tank with a harder, flatter seat but that is about it.
Motor. For a bike with 50 hp the KTM is very smooth. It really feels kind of four stroke like in that the power is very linear with no real snap in the mid range. It is just strong from bottom to top. Heaps more bottom end than the RM. The track was really tight and the fastest part of the track is third gear wide open for about 2-3 seconds so I didn?t really get to test top end but off the line with a concrete start pad I pulled one holeshot and one second. I couldn?t get off the line as quick but hit the dirt and I ripped back through the pack. The hardest thing was keeping the front end down. Definitely a quick motor
One thing I did find was how responsive the throttle was. It was like riding an injected 4 stroke, breathe on the throttle and the bike snapped forward, especially coming out of really tight second gear turns.
On those tight second gear turns, the RM had to be clutched to get around them and pull out of them. I found the best way to get the KTM out was no clutch and let the strong bottom pull it out. It resulted in less wheelspin and better drive. Even with a Pro Circuit pipe and R304 muffler the RM doesn?t keep with the KTM and the KTM runs a 13/48 gearing which does hold it back a little out of corners but adds to the tractability
The motor does have a knock to it though. I was sure it was piston slap and was getting really worried so I asked another guy with a KTM 250sx about it and his sounds the same so all good. It also vibrates a lot more than a jap bike but once the gate drops I don?t notice it.
Overall very happy with the motor
Brakes. 260mm of Brembo goodness. Need I say more? No? well I will. One place where I would make up the most ground on anyone was under brakes. I could go in faster and deeper and then just pull the brakes and make the turn much easier than anyone else out there. The only other guy that could come close was on an sx-f, but his heavier bike didn?t stop like mine. Even with a 270mm rotor on my RM it doesn?t come close to the KTM.
Handling. Let me start by saying that at 85kg plus gear both the KTM and RM are sprung too soft for me, especially in the front. Both bikes would dive in the front under brakes and if there were rough braking bumps the front wheel would deflect on both bikes. Once I had heavier springs and valving done in the RM it was much better so I know my first port of call for the KTM.
After practice I was questioning the purchase of the KTM. It just didn?t handle. The front wheel pushed through corners and then once it stuck the back end would come around. Had I got so used to the legendary handling of the RM that the KTM just felt like crap?
I got back to the pits and slid the fork up in the triple clamps a couple mm, checked and readjusted sag and dropped 2 psi out of each tyre. WOW, this was a totally new bike. Think about taking a corner and it was there, rail through the corner, twist the gas and the bike just drove dead straight. There was no fishtailing usually associated with a 2 stroke, the smooth powerband and chassis ment that the bike just hooked up and drove exactly where I wanted it to go. It was kind of like the RM into turns and a 250f on steroids out of turns. The smile on my face was unmissable in the pits after the first moto (where I went from dead last in a first turn pile up to 3rd).
One big improvement of the KTM over the RM is its stability after an over jump. When I had stock suspension on the RM in the event of a big over jump the bike would kick sideways and it would be hard to pull up for the next corner. No matter how big the over jump on the KTM it stayed dead straight and rode straight to the next corner
During the day I made smaller changes to the clickers to get the bike to settle on the ever rougher track and it will be off to get stiffer springs and maybe some valving work and I think it will be the perfect bike.
Overall I am very pleased with the bike. It isn?t night and day better than the RM but it is better and with the right spring rates I think it will be awesome. It does remind me a lot of the late model four strokes, the ergonomics, the tractable power (for a 250 2 stroke) and the stability of the chassis but is still distinctively a 2 stroke. Throw in the detail and quality of the parts that KTM use and I would say hands down that this is the best bike I have ever ridden
Post by: nom de guerre on August 27, 2012, 12:37:42 PM
With regards to the engine, run the red PV spring w/brass screw flush w/case, get a 160 main, 40 pilot, Suzuki NECJ in the 3rd... Really transforms the engine. BUT, if you are happy(sounds like you are), run it!!
Post by: SachsGS on August 27, 2012, 03:39:19 PM
Post by: chump6784 on August 27, 2012, 08:31:22 PM
Good stuff Chump...
With regards to the engine, run the red PV spring w/brass screw flush w/case, get a 160 main, 40 pilot, Suzuki NECJ in the 3rd... Really transforms the engine. BUT, if you are happy(sounds like you are), run it!!
Thanks. I was going to start playing around with that stuff but i also really like the smooth powerband. It really gets the power to the ground even with how much is there
How does the linkage WP suspension of the KTM compare to the RM in the really "hacky" parts of the track?the rear was quite good. It was kicking around a bit under brakes so I slowed down the rebound a couple of clicks for the last moto and it settled it down a bit more. I think you could contribute a lot of that to the front being so soft and allowing the front to dive too much
Post by: _X_ on August 27, 2012, 09:51:46 PM
Post by: scotty dog on August 27, 2012, 11:11:07 PM
Post by: Stusmoke on August 28, 2012, 01:22:02 AM
Good stuff Chump, cool write up, glad to see ya hapy with the new beast
X2 mate. Nice work. You got any vids for us?
Post by: chump6784 on August 28, 2012, 04:42:26 AM
Post by: msambuco on August 28, 2012, 05:13:14 AM
Post by: factoryX on August 28, 2012, 05:42:54 AM
Post by: TMKIWI on August 28, 2012, 07:35:16 AM
Post by: dean100yz on August 28, 2012, 03:24:05 PM
Im in the same situation and just tried out a '12 KTM250sx at a local sand track yesterday.
What you said sums it up. I didnt find the handling as precise as the RM on the front so maybe its a setup thing
As for those brakes
I've ridden Jap stuff too long, damn things nearly pitched me several times!
Post by: chump6784 on August 28, 2012, 08:36:14 PM
Good info from a guy who likes both bikes. Your short test info helps KTM and RM fans. I for one did not know the KTM had smooth power through the RPM range. Everything I read about the SX talked about high peak HP. After putting a PC pipe on my YZ250 and not being able to handle the quick response over the stocker I figured I would not like the SX. Based on your report it has a great managable powerband. Good to know.Although the power is smooth there is a lot of it. You still need to be careful with the throttle as it is really responsive but there is just not the "hit" of the jap bikes
here is a spreadsheet graph i have made up of different bikes from dyno charts and MXA's dyno readings over time. You will notice how smooth the KTM power band is and no other bike on the chart ever beats it.
yes i know not all dyno charts read the same and conditions will affect readings but this is what i have got.
Post by: Stusmoke on August 29, 2012, 10:34:05 AM
Post by: TMKIWI on August 29, 2012, 10:58:58 AM
Just looking at that graph makes me scoff at the powerbands of four strokes. And the lack of power compared to the 250s. It astounds me how people can possibly defend their purchase of a 250F
The problem Stu is they (250F's) go round a track faster then dyno figures show.
Power is not everything.
Post by: dean100yz on August 29, 2012, 04:42:11 PM
Just looking at that graph makes me scoff at the powerbands of four strokes. And the lack of power compared to the 250s. It astounds me how people can possibly defend their purchase of a 250F
The problem Stu is they (250F's) go round a track faster then dyno figures show.
Power is not everything.
Yeh true point that
Post by: citabjockey on August 29, 2012, 06:40:22 PM
Also, the fact that a 33HP 250F matches the lap times of a 45+ hp 250 means that peek power only means so much. Now, if someone could put together a 2T engine that makes 35 or so HP but over a much wider range, and keep it light, and keep it reliable, and keep it cheap, it might end up being a faster bike for the masses!
Still, a 50HP KTM SX must be very entertaining to ride. Would love to try it sometime.
Post by: Stusmoke on August 30, 2012, 09:13:30 AM
Just looking at that graph makes me scoff at the powerbands of four strokes. And the lack of power compared to the 250s. It astounds me how people can possibly defend their purchase of a 250F
The problem Stu is they (250F's) go round a track faster then dyno figures show.
Power is not everything.
Touche.
The other true point is that the 250F powerband requires you to run it up pas 12k rpm. Talk about stress on all those flailing parts. There is a reason that they are expensive to maintain (sometimes).
Also, the fact that a 33HP 250F matches the lap times of a 45+ hp 250 means that peek power only means so much. Now, if someone could put together a 2T engine that makes 35 or so HP but over a much wider range, and keep it light, and keep it reliable, and keep it cheap, it might end up being a faster bike for the masses!
Still, a 50HP KTM SX must be very entertaining to ride. Would love to try it sometime.
In most cases yes, but look at the powerband of the 250sx; its pretty linear for a two stroke. 8500 RPM peak horsepower (by my eyes) and falling down in the RPM ranges wouldn't be a disaster. Hell all of those 250s are pretty linear. So I reckon running it like a fourstroke would keep it perfectly competitive in the power department but maintaining the light weight advantage through the corners
Post by: Micahdogg on August 30, 2012, 05:37:59 PM
The KTM lugs hard, pulls smooth and has more on top. It's not as exciting, until you start laying down some good laps and realize how well the power is produced. Mine also has a knock sound, but I think it's probably due to the 93 octane I'm running. I bet it would go away if I used something closer to 100.
The brakes are just stupid. There is no need for this much brake. I'm never even close to 50% effort on the front brakes. Most of the time I just breathe on the lever and the bike stops fine.
Ergos are pretty close.
Handling, I do feel like the RM handled better. I only have about 25 hours on my KTM, but I feel like I have to move around more (stay up front more) in order to get comfortable in the handling. I'm still not there, but it's not like I was always comfortable on the RM. On more days I felt dialed on the RM's handling though. The KTM is tolerable though. Keep in mind I have the PDS shock too.
They hydraulic clutch is nice. I never wanted one, and after just a few rides I like it so much that I would retrofit it to another bike that didn't have one standard.
Overall, it's a very nice bike and I have no regrets. The powerplant felt so good stock that all I did was lean the clip one notch (to cut down on the spooge) and that's it. I'm not even messing with needles or the PV spring. Between the motor, brakes, clutch and nice new package of the 11+ KTM, I can more than handle any negatives.
Post by: chump6784 on August 30, 2012, 10:19:11 PM
One complaint. Vibration. I am surprised every woman doesn't have a ktm tucked away for those lonely nights.
Post by: _X_ on August 30, 2012, 11:55:22 PM
Post by: chump6784 on August 31, 2012, 03:16:50 AM
Post by: TMKIWI on August 31, 2012, 08:34:22 AM
Post by: _X_ on August 31, 2012, 11:53:02 AM
Post by: gpnewhouse7 on August 31, 2012, 09:19:54 PM
Also, the fact that a 33HP 250F matches the lap times of a 45+ hp 250 means that peek power only means so much. Now, if someone could put together a 2T engine that makes 35 or so HP but over a much wider range, and keep it light, and keep it reliable, and keep it cheap, it might end up being a faster bike for the masses!
You mean like a KTM 200 exc?
Post by: chump6784 on August 31, 2012, 09:34:44 PM
seat bounce! new school front of the bike huh. look good man.
No seat bounce, just trying to soak that sucker up.
Post by: _X_ on August 31, 2012, 11:19:13 PM
Post by: citabjockey on September 03, 2012, 12:08:31 AM
In most cases yes, but look at the powerband of the 250sx; its pretty linear for a two stroke. 8500 RPM peak horsepower (by my eyes) and falling down in the RPM ranges wouldn't be a disaster. Hell all of those 250s are pretty linear. So I reckon running it like a fourstroke would keep it perfectly competitive in the power department but maintaining the light weight advantage through the corners
Linear is not the same thing as "flat". When you look at these dyno charts you see the linear climb of the 250's (and also -- to a much smaller extent the 250f) in the slope of the line. If someone could take a 250 motor and simply clip off this top portion -- limit it to between 35 and 40 horsepower but have it make that power starting at 4k and the same at 5k and 6k and 7k all the way up to 10k, THAT would be a flat powerband and much wider than even the spread of the 250f.
Now such an engine would not win any drag races against a 50HP SX BUT in any kind of technical stuff it would be more predictable and require less compensation by the rider to dial in exactly how much power is desired (for example, as you accelerate in a place where the tire can only stand 25HP before breaking loose you have to be backing off the throttle as the engine makes more power just by RPM). Easier to ride. Also less interesting to ride and some would say less fun as well but might end up being a faster bike for lap times -- at least at an amateur or lower levels. And because it would be stressed less than the 50HP models it should last forever.
All that said, the best riders can deal with the steep power curves and can take advantage of 15 or so extra ponies -- so the top pros would always be put on the bikes with the best power. Because of this the public will never get to sample a machine like this -- the manufacturers have no reason to build it. I do think it would be interesting to put joe average racer on it and see what would happen.