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Old 05-14-2007, 09:44 AM   #1
hartzpad OP
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KTM 450/525 owners: Is this how all EXC's are?

I've got a plated, modded Yamaha WR426 that has been 100% reliable (over 13000 miles of dual sport use) and a great trail/street bike, just needs electric start and a 6th gear.

I was set on a 2003-2005 KTM 525EXC but I've ridden 2 used 525 MXC's lately and both had very strong low end but little to no top end. My WR seems much more fun to ride, it has good low end power (heavy flywheels helps on trails) a strong mid-range hit and it pulls hard to redline. The KTM's I rode have great low end power until a perceived 6-7,000 RPM's where the power just almost stops, you almost have to short shift it to keep accelerating. I love everything about the KTM's, the ergo's, the looks. the seemingly easy maintenance, and especially the 6th gear. I've been told that it is the lower compression ratio (11:1 vs. 12.5:1) and longer stroke that keep the 525 from "feeling" fast like a WR with its high compression and high revving 5 titanium valve engine.

Someone suggested that I try out a 450 EXC because they have better top end power and more snap that the 525's, is this true? I ride from 4500-9000' if it makes any difference.

Is this strong low end but not much top end power typical of all KTM 525's and 450's (EXC's and XC-W's)? I desperately want to like the KTM 525, but I need to know if this is normal on other bikes? Should I expect the KTM 450 EXC to be different than the 525?
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Old 05-15-2007, 05:54 AM   #2
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You need to learn more about what KTM your riding. Some MXC are 5 speed trans and some are close ratio 6 speed trans. You need to ride an EXC that has a 6 speed wide ratio trans and will run close to 100 MPH top end with 14/52 gearing.
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Old 05-15-2007, 06:56 AM   #3
Some Dude
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Not that you want to buy a bike with the intention of modding it right out of the shoot but,............I came off of a YZ400F with shorter gearing and fmf powerbomb and that was it. No flywheel weights or such to make it a better trail bike. I was used to the hit and especially with the lower gearing it had super snap. However I got tired of kicking and wanted a taggable bike that could chug when needed and snap would be nice. I got on an 05 525 exc and immediately felt at home and improved my tight single track riding instantly. However as I got more aggressive I started to miss the snap of the YZ and started to hear a slight knock in the 525. So I did some research and decided to overhaul the head with oversized stainless valves. This will help cut down valve adjustment intervals as the new valves and seats will not wear as fast and flow much better. While I was at it I went ahead and installed a higher compression 98mm piston (540cc kit). The results were amazing and the bike is just plain old fast in the tight stuff as it is on the open straights. Cost for parts is under $900 if you do the tear down and re-assembly. I would do it all over again. You can find an older 525 for $2500-5000 and then plan on spending another $1000 to make it more reliable and less maintenance. I went one step further with a Vortex CDI and having selectable ignition maps really added the snap into the equation.

I also have a 450 but in MXC trim. It is mildly snappier then the stock 525 exc, however does not chug up hills as well with the MXC gearing and lack of displacement. All of the 450's except the SXF or XC have the longer 525 stroke and only difference is the bore size.
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Old 05-15-2007, 07:16 AM   #4
hartzpad OP
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Quote:
Originally Posted by BMW Atlanta
Not that you want to buy a bike with the intention of modding it right out of the shoot but,............I came off of a YZ400F with shorter gearing and fmf powerbomb and that was it. No flywheel weights or such to make it a better trail bike. I was used to the hit and especially with the lower gearing it had super snap. However I got tired of kicking and wanted a taggable bike that could chug when needed and snap would be nice. I got on an 05 525 exc and immediately felt at home and improved my tight single track riding instantly. However as I got more aggressive I started to miss the snap of the YZ and started to hear a slight knock in the 525. So I did some research and decided to overhaul the head with oversized stainless valves. This will help cut down valve adjustment intervals as the new valves and seats will not wear as fast and flow much better. While I was at it I went ahead and installed a higher compression 98mm piston (540cc kit). The results were amazing and the bike is just plain old fast in the tight stuff as it is on the open straights. Cost for parts is under $900 if you do the tear down and re-assembly. I would do it all over again. You can find an older 525 for $2500-5000 and then plan on spending another $1000 to make it more reliable and less maintenance. I went one step further with a Vortex CDI and having selectable ignition maps really added the snap into the equation.

I also have a 450 but in MXC trim. It is mildly snappier then the stock 525 exc, however does not chug up hills as well with the MXC gearing and lack of displacement. All of the 450's except the SXF or XC have the longer 525 stroke and only difference is the bore size.
Yep, I've been told to either start with an SX motor and add 5th and 6th gears, or take an EXC motor and add larger displacement, bigger valves, and raise the compression to wake up the EXC motor and give it snap comparable to a motocross bike. I don't want to spend money tearing down the engine on a 3 year hold bike just to make it comparable to my WR in the power delivery department.

I'm thinking about looking for an '01-'02 KTM 520 EXC, they are quite a bit cheaper than the 525's with most of the same components. I've also heard that their power delivery is a little more raw than the newer bikes.
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Old 05-15-2007, 11:20 AM   #5
Some Dude
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Quote:
Originally Posted by hartzpad
Yep, I've been told to either start with an SX motor and add 5th and 6th gears, or take an EXC motor and add larger displacement, bigger valves, and raise the compression to wake up the EXC motor and give it snap comparable to a motocross bike. I don't want to spend money tearing down the engine on a 3 year hold bike just to make it comparable to my WR in the power delivery department.

I'm thinking about looking for an '01-'02 KTM 520 EXC, they are quite a bit cheaper than the 525's with most of the same components. I've also heard that their power delivery is a little more raw than the newer bikes.

There is no comparing a YZ or WR 450 to this "540" now. It's got the raw power of a modded LC4 and smooth as butter power delivery. I'd never go back after tasting this.
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Old 05-15-2007, 12:54 PM   #6
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I have an 07 450 EXC and love the power only have a couple hundred miles right now but it will get more . I went down 2 on the front sprocket before I rode it , it was poor untill I tuned it and adjusted the carb where it needed to be after around a hundred miles . Before the carb adjustment it would not idle , wouldn't idle down after releasing the throttle and was otherwise extreamly aneamic as most EPA tuned bikes are . After needle adjustment , idle screw adjustment and canister removal it is a blast to ride , very predictable power , plenty of it and good low end . The only complaint I have is the close ratio trans , I am used to more gear spread . Cant say much for the saet right now except the new one is on the way . SEYA
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Old 05-15-2007, 02:39 PM   #7
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I've heard the 525s run out of juice up high but have gobs of torque down low. I've never ridden one, but I do own an '07 450 EXC and it wants to pull and pull like there's no tomorrow and the engine feels light and snappy. It's got way more juice than I dare fully tap and I don't find it lacking for anything down low. For a dyno comparison of the two bikes, JD Jetting has some good graphs here:

http://www.pbase.com/jdjetting1/450_525&page=all

Scroll to the bottom for the graphs. As you can see the 525 is making a lot more torque down low but the 450 holds the power and torque longer up top.

In either case, you'll definitely want to rejet and do something about that pipe restrictor (applicable only to the '07). I went with 14:49 gearing, the JD Jet Kit along with their AP diaphram replacement, and an Akrapovic slip-on and couldn't be happier.
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Old 05-15-2007, 03:54 PM   #8
EMrider
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Quote:
Originally Posted by hartzpad
I've got a plated, modded Yamaha WR426 that has been 100% reliable (over 13000 miles of dual sport use) and a great trail/street bike, just needs electric start and a 6th gear.

I was set on a 2003-2005 KTM 525EXC but I've ridden 2 used 525 MXC's lately and both had very strong low end but little to no top end. My WR seems much more fun to ride, it has good low end power (heavy flywheels helps on trails) a strong mid-range hit and it pulls hard to redline. The KTM's I rode have great low end power until a perceived 6-7,000 RPM's where the power just almost stops, you almost have to short shift it to keep accelerating. I love everything about the KTM's, the ergo's, the looks. the seemingly easy maintenance, and especially the 6th gear. I've been told that it is the lower compression ratio (11:1 vs. 12.5:1) and longer stroke that keep the 525 from "feeling" fast like a WR with its high compression and high revving 5 titanium valve engine.

Someone suggested that I try out a 450 EXC because they have better top end power and more snap that the 525's, is this true? I ride from 4500-9000' if it makes any difference.

Is this strong low end but not much top end power typical of all KTM 525's and 450's (EXC's and XC-W's)? I desperately want to like the KTM 525, but I need to know if this is normal on other bikes? Should I expect the KTM 450 EXC to be different than the 525?
The EXC 450 and 525s have long stroke motors. So yes, it is typical that they have excellent low end, a strong but smooth midrange and modest incremental power above 7k rpm. The have excellent overall power and will go fast as hell, but the sensation of the power delivery is quite different from an uncorked WR or YZ. If you want a snappy feel, gear it down. With a six speed wide ratio you will still have plenty of top speed. Or, consider a Husky TE. The TE has a short stroke motor and a close ratio tranny and feels much more YZ like in terms of power delivery. I own both an EXC and a TE. Love them both. If you want to maximize the thrill of a strong motor, get the TE. For maximum versatility, get an EXC.
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Old 05-15-2007, 09:23 PM   #9
El Toad Man
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Often it's a perception thing. Two engines with the same top end, but one has a stronger bottom end, which makes the top end "feel" less impressive.
With more bottom end, you find that your ground speed is often faster, but you don't feel as fast.

Do you want a bike that feels fast, or is actually fast. I ask that as a serious question, as I've had bikes with loads of linear smooth power, but they're not necessarily the most fun. Gimme a good enduro 2 stroke anyday!

The first of the 525's (up to '04) feel to have a more exciting, more pronounced midrange hit than the post '05 models. In reality, the new ones just have more bottom end.

Stroke length limits maximum rpm, but longer stroke does not necessarily mean more bottom end. It has more to do with the engine tuning (cam timing/carb/ignition etc etc) Adding to the "long stroke = more torque" myth is that longer stroke often results in a heavier crank, meaning more flywheel inertia.
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