horse power ratings seen with my own eyes!

Just back from the local ktm dealer here and they dyno'ed a 520 sx stock and saw 46.7 hp then put on a new fmf power core IV silencer and saw 47.6 hp the major thing was that the silencer did everything that fmf said it would. "It comes on sooner and stays on longer!

they also dyno'ed a stock sx 250 and saw 41.9 hp and 29.8 ft lbs of torque.

That sounds like a very small gain for a exhaust system.

Yes, it would be a small gain for an exhaust system, but it appears that he is only talking about changing the silencer.

Yes that is all they did was the silencer but what affected it most was with the air box cover off it could reach fifty horse power!

I just thought the numbers would be interesting to see since some guys say thier bikes are more than fifty Hp......stock!

Wow, that must have been a "sick" machine. I have seen dyno test results, and they are ALL in the 52-54 hp range. As a "physical proof"-- I am 6'2" and weigh 250 lbs geared up.I straight line raced a YZ426F 10 times. The YZ had a full pipe, and was in perfect tune. They are supposed to have 47hp stock. The rider of the YZ weighs 165lbs in full gear. My 520 is basically stock, with only holes drilled in the airbox cover. I absolutely ran away from him time after time, with no problem. Also, I have seen dyno differences from different brands of dynos. I know all about HP, because I drag raced for years (1965 Barracuda-9.70@147mph)There is a good possibility that either the bike, or the machine was off. I have seen 10-11 dyno graphs for the 520, and the lowest one was 49.7hp, and the highest was 56hp.


2001 520EXC KTM

1974 Suzuki TM125

1977 Yamaha DT100

1984 Yamaha DT100

1977 Trail Horse minibike

1986 Honda XR350

Don't forget forget that 2 different dynos can give 2 differrent hp figures. :)

Are you sure an exc and a sx would not dyno differently?

Out of curiosity, how much torque did the 520 make, and at what rpm?

About these holes you drilled in your air box.... I have the same bike as you, and the only problem with the power I have found is "quick rips" off idle, it wants to sometimes cough and just quit. Do the holes solve that ?? Just curious if you have the same thing happen... Its only if I let the bike get down to near idle in a turn then need quick wide open power to clear a jump right out of the turn... Thanks for anyone else's help too....

The problem with dynos is that they are not consistent enough to compare one dyno graph from one dyno, with another dyno graph from someone elses. You can't say 'oh but my bike makes over 50hp coz i saw it on a dyno'. Big deal. A dyno is useful because you can measure the difference a modification makes to the bike, just like the exhaust mod in the first post. Outright horsepower figures are pretty much irrelevant. We are talking about rear wheel horsepower, so there are other factors to consider, such as gearing and rear wheel size.

its great that your 520 eats 426's, but again there are other factors to consider. The power delivery on your 520 is like a sewing machine, silky smooth, so it grabs and moves forward, smoothly. A 426 is pretty damm aggressive in its power delivery, so it needs heaps of traction and a rider skilled to keep it hooked up and driving, rather than sliding and spinning. The only way you can say your bike makes over 50hp is if you take it to every dyno operator in your area, and if it makes that figure on all of them, then i guess it does (but make sure they have all been calibrated). To say it does because it will drag off someone elses bike is, well, a bit unscientific.

Also, is the 47hp stock power figure of the 426 at the engine or at the wheel? If its a factory quote, then it must be at the engine, right? If this is so, why are we comparing rear wheel figures with engine figures? As a drag racer, surely you must see the errors in your statements. What power does your drag car make? At a recent horsepower event here in oz, a 5.7 litre twin turbo V8 made 850hp at the wheels on only 15psi boost and on avgas.


The off idle bog is typical for the Yam's and for all 4-strokes, as what i know about it.

In most cases it's a lean spot, there are different ways to solve that (as much as possible)

First try to enrich the idle circuit by losing the feul screw in steps of 1/4 turn (cclw) and try.

if this doesn't work try to raise the idle a bit.

if you're still not satisfied raise the needle 1 clip.

Good luck.



'99 WR400 F, YZ exhaust, throttle stop trimmed, WR timing, airbox cover removed

There is a mod that can help cure this that wastalked about in the YZF forums. I think they were calling it the B.K. (Brian Kinney) mod. Worked for the YZ 426...maybe the same for the KTMS????? Who knows?

The holes in my airbox sure helped. I got a kit of 10 1" breather inserts from my local dealer, and took a 1" paddle bit, and drilled holes in my airbox cover. The breather inserts come with small little filters in them alresdy. I also have the James Dean jetting (OCEMN neddle 4th clip, 165 main). The factory bike Smets rides has a bunch of holes too. The "pop and stall" condition you are describing is sure helped by this.

Ok, DOC I will give you a response. Of course dynos are different-- that is why I base my conclusion of HP to be an average of 52-54 for the different dyno charts. Ummmm-the YZ426 was tested at the same time, on the same dynos, and its average was 47--not the "claimed" manufactures rating. So, yes, these ratings were at the rear wheel, as MOST dyno charts are.As a FORMER drag racer, I do not see any "error" in any statements I have made. My drag car has not been Dynoed, but with the many available computer hp programs available, I recall it being in the high 700s. I have not raced it since 96. however to enlighten you, I not only drag raced, but I also owned a Mopar resto/performance shop, with a 4 car drag team! I have completely restored quite a few Mopar musclecars, and a few classic oldies. I have also designed, and built many drag motors. So I would hope by now you understand--your flamebait reply to my post is BS. I stated "different dynos give different results" in my post. I also gave a physical example of the comparative HP and performance of the two bikes, hoping to provide useful info. So I want to know, what errors did I make in my statement? What was even the point you were trying to make? I have seen probably 10-11 dyno charts for the 520-- I cant recall if they were EXC, or SX, but every one I have seen, has not only the 520 producing more peak power, but if I recall, from 3500 rpm to 8500 rpm, the KTMs curve was substantially better, at one point 11 hp more!


2001 520EXC KTM

1974 Suzuki TM125

1977 Yamaha DT100

1984 Yamaha DT100

1977 Trail Horse minibike

1986 Honda XR350

Thanks, but why don't you re-read your first statement in your first post, quote "Wow, that must have been a "sick" machine. I have seen dyno test results, and they are ALL in the 52-54 hp range". Like i said, big deal. Just because your bike cracks 50 hp on your local dyno doesn't mean anything. To say someones 47.6hp bike on another dyno makes it a "sick machine" is, like you say, BS. Is that making sense to you?

You didn't make a good come back on my comment about your "physical proof". Like i said, the power delivery on a 426 is much more aggresive, so it needs to be in the right hands to make your "physical proof" mean anything. Do you think you could pull the holeshot at your local track with Mr.McGrath on a 426 and you on your 520? As you are a FORMER drag racer, you should know that there is much more too it than just holding on the gas. There is a technique, and it takes quality practice to perfect it. A quality rider like Jeremy should be a good example of this. He does pretty well, agree?

When you mentioned your work with MOPAR Muscle cars, i automatically assume you work with carburettors, right? If so, that answers my question about your own drag car. I was assuming it was fuel injected, and my question was how did you tune the ignition/fuel maps without the aid of a dyno. Funny how you know all about HP, but your own car hasn't been measured, tee hee! Over here in OZ we have 5 litre touring cars making well over 600hp on 98 octane fuel and without forced induction. These motors still run 16 valves, but can make the numbers with advanced programable engine management systems (Motec in this case). I remember reading that your Nascars are restricted to carburettors, and was wondering what sort of figures those engines were making?

Ok, DOC I was trying to remain civil. Now, I will tear your assinine comments to shreds, junior. First off, to respond to your assault on my saying it was a sick machine, it would be obvious to me, if the bike only put out 47 hp, and all other dyno tests show substantially higher, then the bike would have to be "sick", unless the dyno is waaaayy off, which a 5hp difference is waaay off, especially at these "little" hp figures, when most dynos are used for far more hp-- When someone tells you to tie your shoes, do they tell you step by step, or do you have enough intelligence to figure the rest out (I did not think it was necessary to bring up the possibility of the dyno being off). I did not feel the need for going into step by step detail on dynos, and their problems, and how different types of dynos have different inherent problems. I would hope most of the people that read these boards would have enough intelligence to "see the obvious". Obviously in your case, thats not enough. What basis of training or knowledge are you basing your pathetic statements on? I see you are a computer programmer. Now, to explain to the ignorant about power to weight ratios irregardless of the "aggressive" as you put it power delivery of your beloved 426s. I weigh 250lbs in gear. the other rider weighs approx 170 in gear, thusly bringing the total weight of me and my bike to 496 lbs, and the 426 and rider to 426 lbs.Sure, I could beat Jeremy in a straight line drag race on a big, open field--it really dosent take much skill to do a full on acceleration run(the only skillful part is the launch, the rest is hold it wide, and shift as needed).Ok, now your hopefully seeing the "physical proof" evidence. There is a 70 lb weight difference between us and our respective bikes. If you look at empirical test data (the dragging we did could certainly even be called a "double blind experiment")then even you, could understand the conclusions drawn were correct. And by the way, the other rider is an "A" Enduro and Hare Scrambles rider, --I would certainly say he knows how to control his bike, as well as a starting technique. I am actually the one who had trouble getting my 520 to hook, even with a near new Michelin 130 profile tire. Your immature comment on "teehee" you dont even know how much hp your car is putting out, I find hilarious! I dont care how much HP a piece of paper tells me-- I care what happens when the lights turn green, and I run consistant times.

Personally, I dont care what you have in OZ,BTW WHAT do YOU have??? I feel like I am talking to a 13 year old, who says, "cool car, but I know someone who has a top fueler". Who gives a sheeite over what someone else has? Did you feel you were impressing someone? I believe our NASCAR cars make 7-800 HP. I am getting the impression if brains were dynamite, you coulden't blow your nose! Quit while you are behind (this far)wanker!


2001 520EXC KTM

1974 Suzuki TM125

1977 Yamaha DT100

1984 Yamaha DT100

1977 Trail Horse minibike

1986 Honda XR350

[This message has been edited by trl junkie (edited September 20, 2001).]

WOW a bit of dog fight going on over HP figures. Any one know the HP of a 2002 KTM 400 EXC at the engine & rear wheel thanks

Such a mature age man, yet still hasn't mastered the control of his own emotions. The "tee hee" was to break the ice a bit. This is a discussion, not a war, lighten up! But now, while your blood is boiling, im starting to find this amusing!.

I was expecting you to comment on your first statement that, quote again "There is a good possibility that either the bike, or the machine was off." I'll assume that machine means dyno, and if it does, then you have just contradicted yourself by your first (as above) and last posts (I did not think it was necessary to bring up the possibility of the dyno being off). But this is okay, because it isn't really important to my point.

A dyno is really useful because it measures the difference, if any, a certain modification does to a engine. In the very first post, captain ktm stated that he saw a bike make 46.7hp before being worked on, and then 47.6hp after the mods. Look, by the use of a dyno, we have seen that the pipe makes a difference. Lets all praise dynos! But, where do you have the right to say that the bike and or the dyno are "sick", just because you have seen 50+hp come from these bikes on another dyno. Its irrelevant i think, just like you don't care what power your drag car makes (but if it was mine, i would love to know). I just can't believe that you have worked in the industry but haven't realised the real use of the dyno. How do you build, and continue to modify a drag car without one? How do you know if the mods you are doing to a particular engine are for the better, or for the worse?

Im thinking that you are one of those big talkers at the pub that likes to impress young girls with your talk about your drag car and your 54hp KTM. Not to mention the fact you are a FORMER drag car racer that also found the time to work on MOPAR muscle cars, and a few classic oldies thrown in. You must include the many drag motors that you have built, as that is very impressive but, don't forget about the performance shop which had a four car drag team! Thats right, four cars! At this stage, im just wondering did you feel you were impressing someone?

I was just wondering if you were using carburettors or fuel injecttion, because in this age it is very interesting to compare the two. I don't own a touring car, and never will, but don't you, a mechaninc and FORMER drag racer, find it interesting that a pushrod 5L V8, drinking 98 octane fuel can make 600hp or so with the assistance of advanced fuel injection? I was thinking you were going to give me a few facts about how far they have or haven't progressed in the last few years. After all, it would be fool hardy to talk to you without trying to draw some of your wisdom in other areas.

Im starting to get worried, because i feel that you might snap soon, and probaly bash your wife and kids if you have any. This statement alone may push you over that limit. I don't want to do that, as there is already too much violence in your part of the world, with way too many deaths. I still think about the terrorist attack on the Trade Towers, and hope that the families of the victims can pick up their lives soon, even though it would be difficuld to do. The above argument may be based on humor, but this statement is not.

OK OK OK,........GENTLEMEN! We must be civil about this whole thing!!!!!!



I do know that dynos run differently all over the world.

As far as the ktm being sick......I HIGHLY DOUBGHT IT!

I rode this thing on the weekend and it ripps!

I will never buy one because I love my 400 exc.

but I wont get into how many hp it has because Im only affected by torque to the ground!

Another thing here is the weather and elevation of where the bike is being dynoed.Most car buffs use a corrected hp number to "even" out the playing feild.I will say this a bike in Colorado is not gonna put up the numbers that the same bike would in NY.My half a cent.

ok you ktm lovin meatheads-first of all you losers, it is a well known fact that no two mass produced machines will make the same hp/trq on any to argue like children over this is ridiculous.a dyno should be certified every so often so it gives consistent readings.if you took 5 bikes off the assembly line they would all have different readings-so maybe its better to say that a certain bike has produced in stock form 47-54 hp on a dyno.end of story,by the way how many 520's have won a national outdoor/supercross race?happy arguing.

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