I was just reading over a dirtbike magazine I bought a few months ago. There is a guy in the mag who turned a ktm520 exc into a 540 with 78 HP. The bike is claimed to still be very reliable. My question for you guys out there is why are people getting their raptor(or any other quad for that matter) punched out to 690's, 720's, etc. to get around 70HP. It seems that since the raptor already has a bigger, higher tech engine than the ktm, it should be possible to get a ton of power without resorting to big bore kits.
If i'm overlooking something, feel free to point it out.

JaMeS

 

you should know that dyno on a motocross is different since there is less power loss to the wheels than a quad....

 

honda predator...Lets figure that if the ktm540 engine was on a quad, it would put out about 73-74 RWHP instead of 78 RWHP as on the dirtbike. My argument still holds.

JaMeS

 

yeah but then it depends on the engine...see a stock ktm520 puts out 50hp while a raptor660 only 35.......

 

You're forgetting how corked up a stock Raptor is....do a simple un-corking, and the power levels are much closer. (yeah I know the Raptor's engine is much larger, but the KTM was designed as a higher-stressed racing engine) I wonder how much power that KTM would produce if it was as stopped up stock as the Raptor is?

 

There are going to be many factors. I am not a builder, but I know there are major differences. The heads are different, the Rap head can only flow so much, valve design and length, cams, etc. I bet if you called Trinity or any reputable builder for that matter and said, "hey, I want a 90 horsepower rap and money is no object, it could be done!

I have a question. Explain to us all "how" the Raptor engine is higher tech then the specific KTM motor you speak of? 5 valves isn't going to be the answer.

Money produces power and reliablity is another word of caution!

 

swytak
I said feel free to tell me if i'm overlooking something. I may have overlooked the fact that the raptor does not have a higher tech engine. sorry about that. Don't get mad at me. It still seems to me that if the raptor was outfitted with, larger valves, a higher lift cam, bigger carbs, different exhaust, a ported & polished head, High compression piston, etc. I see no reason why the raptor would not produce power in the 70+ HP range. The raptor motor(as I see it) has a whole lot of potential. It is alright to disagree, I am open to other people's opinions.
Thanks for replying everyone.

JaMeS
P.S. Just because I think the raptor engine is capable of making 70HP without a Big bore kit, does not make it so. That is just my opinion so take it with a grain of salt if you wish.

 

yamahagye,

No offense takin, just giving my thoughts as well!

If you look back to where the Rap motor was initially brought in to production, you will see that this motor is an old design. Atleast 10+ years old, not what I would consider "high tech".

You said that if the Rap motor had a high comp piston, overbore, big cam, carbs and exhaust, why wouldn't it make 70+ RWHP? They do! But, most people only want to go so far. The more power the more chance for it being unreliable. Running on the "ragged edge" as some would say, isn't much fun for most.

Regarding your thoughts on dyno #'s for the KTM, cycle frame vs. quad frame, the difference will be more then just 4-5 HP. The motor in a quad frame has to turn mroe then double the weight of the cycle rear end. Just some other things to think about.

Again, I'm not getting mad at all, just giving "my thoughts". Just to make this perfectly clear, I don't know all or even know a little compared to some others on this forum. So I too, don't want to mislead anyone!

Swy

 

Incase you never noticed, why 4wheelers seem to have lower HP's it's because of the Tranny. The tranny is a weak spot on super high HP 4wheelers, because there is so much more traction, compared to a dirtbike, thus until makers can come up with a stronger tranny, 4wheelers will always have to suffer through lower HP numbers than dirtbikes.

 

swytak
Since the raptor engine is an old design(like you pointed out), I guess it has its limits. Care to argue about why the bomb ds650 does not put out 70HP?lol, j/k. Lets not even go there. Thanks for replying everyone.

JaMeS