Maintenance & Technical > KX500 Original

Power question

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Hillclimb#42:
I hear ya'. Its definately weird. I have both a 250 and a 500. The 250 is basically stock and the 500 has some mods, but not maxed out. I hillclimb against all cc's of bikes. The hillclimbs are seperated in their classes by cc's or age groups, but we also race for the overall Fast Time of the Day. Fast Times of the Day are often had by 500's, but there has been plenty of Fast Times of the Day ran by 250's, KTM 380's and 450 four strokes. My buddy rides a 750 Triple 3 cylinder 2stroke, but he rarely wins fast time. When I ride the 500 its like my 250 on constant nitrous, but not always faster on the timer. The 500 does have alot of power, but there are so many things that go into a fast drag race or hillclimb, its freakin nuts. If the 300 can put it to the ground, then you're beat. Power isn't the issue necessarily. We monkey with gearing, tire pressure, tire patterns, Cut tire/ full nobb, rider position, hole preparation and suspension (and more) to get the power to the ground. The power is pretty much the constant, but you have to play with the things you can change to have a quick time.
  My general rule on my other bikes is to gear as tall as you can without a bog, and that is fast. The 500 doesn't play with those rules. It will just roast the tire getting you squirrely or loop out, when geared too high. I would guess that your set-up, riding position or possibly something as simple as 5lbs of air pressure cost you more than being down on power.

greencannon:
Had a 300 and also a 380. Both very impressive both vey fast bikes and engines have the big bore feel. But when my  stock K5 has a fresh top end, fresh tire and fresh clutch plates, click 4th gear and it pulls away like a top fuel dragster....If any bike had a slight chance it would be the 380 on its best day.  Your 15/46 gearing seems a bit high for track racing though. Thats the gearing I would use for high speed runs on the ice. Your losing some serious  acceleration with that gearing that would let you pull away quickly.
As for track racing,  one thing to remember as others have stated, sometimes its easier to go faster with less bike.

SweetTea:
My 300 pumpkin is what got me wanting the big K5 so much!  I was actually looking for a a KTM520 at the time, found it, but the dealer blew it up in front of me trying to get it jetted correctly.  So I quickly ran away from that place and went to another trusty KTM dealer.  Went there looking for the 520 which they didn't have at the time.  But they did have a leftover last year 380 and a 300 on the floor.  So I took a used 380 for a spin (wouldn't let you ride the new ones) and about peed myself!!  Could not keep the front end down!  I came off a KTM400EXC and the difference was stunning.  I was grinning from ear to ear and was set on buying the leftover 380.  However, the dealer talked me into the brand spanking new up to date 2004 300 EXC (Which was probably a grand more, thats why he talked me into it).  I didn't get to test ride it, but he for sured me the power was similar to the 380.  While it was definately a ripper, it just didn't have that adrenaline pumping two-stroke screaming power like the 380 had.  To this day I wish I would have bought the 380, might still have it if I did.  But I can't say anything wrong about the 300, it was one of my most favorite machines, lightweight, super strong, could flick it around like no other.  I think my WR450 is a bit stronger on power, but weighs a ton, and amazingly, I like my WR better than my 525 I had.

So now I finally have the big bore of my dreams, and still haven't ridden it yet, probably another month or so and I'll get to finally ride the big K5.  I'm positive this thing is going to rock my world more than anything I've owned though, if it doesn't, thats okay, I will for sure make it, but I have no doubt!

vwcamper74:

--- Quote from: greencannon on September 22, 2010, 01:55:53 PM ---Had a 300 and also a 380. Both very impressive both vey fast bikes and engines have the big bore feel. But when my  stock K5 has a fresh top end, fresh tire and fresh clutch plates, click 4th gear and it pulls away like a top fuel dragster....If any bike had a slight chance it would be the 380 on its best day.  Your 15/46 gearing seems a bit high for track racing though. Thats the gearing I would use for high speed runs on the ice. Your losing some serious  acceleration with that gearing that would let you pull away quickly.
As for track racing,  one thing to remember as others have stated, sometimes its easier to go faster with less bike.

--- End quote ---

The track was a fairly open high speed type enduro/desert track.  The initial acceleration is where I got the jump but when we got to the higher speeds is where he reeled me in.  His bike kept revving out and picking up speed.  I seemed to run out of revs.  Maybe my bike isn't revving out as far as it should or I needed to gear even higher?
I haven't pulled the motor down since I have owned it so chances are that it needs a freshen up.


I don't want a reason to get rid of the bike as it has been my dream bike since I was a kid. 

Sounds like with it running right, it should still hold it's own out in the high speed stuff :-D

oic0:
What pipe is on it? the most popular pipes for the bikes are the torque pipes but if you try to ride it like a 250 revving it out with one of them on, you'll be disappointed. Especially if its got some big ol dents in it. It keeps pulling a ways past peak but not nearly so hard. Jetting can make a world of difference too.
Ive got a top end pipe on mine, it still pulls on bottom but you can hear the change of tone as the revs climb. Then it goes crazy. I really don't know how it compares on the dyno to the bottom end pipes though since there is a huge shortage of KX500 dyno charts, especially ones that show rpms. The only one ive ever seen was from an ancient magazine shootout with all stock bikes.

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