Frame-off KX500 rebuild Pics / Question re: Power

[martyestes]

Hi all,

I exclusively rode/raced 500's (mostly CR's but also had one KX, a '92) from 1989 - 1996. Since then, I went to 2stroke 250s, KTM 520, 525 and a '08 KX450F.  I still have the KTM 520, it's my dualsport and probably the best bike I've ever owned. Great motor!

I got a hankering for a 500 again, and a friend had a '96 for $500. Runner, and looked like fairly low hours but had been "beginner crashed" a lot. I did a complete rebuild on it. Motor mounts were loose so the frame needed lots of welding around the mounts. Powdercoat. New bore, Pro Circuit suspension, sprung for me, etc. etc. Don't make the same mistake I did - replace those crank seals.  Thing was drinking trans fluid.  Out came the motor and the bottom end is fresh now too. Bike was built for MX. Stock motor except for PC pipe/silencer and Rad Valve.  Jetting is in the ballpark. 

This is coming from an Intermediate-level motocross guy, early 40's but still jumping all the jumps, etc. Took it out last weekend to a somewhat dry/dusty MX track and just wanted to share my thoughts on the motor, mostly because it's not what I remember. Back in the day, when comparing 500's to 250s and 125's, the bottom end was incredible. My biggest surprise with this KX is that you have to rev it more than I remember to make that power.  It is sooo smooth, but not as fast as I thought it would be. So much so that I thought something was wrong. Checked the timing. Drag raced my friend on his CRF450 and I won every time despite the slippery conditions. We switched bikes...same result. But his bike felt faster. The grunt off the bottom and even into the mid is nowhere near the 4-strokes.  The powervalved KX is surprisingly mellow - still fast - but mellow. I think it's all just relative. And maybe on a loamy, softer track it will feel faster than it did last weekend. I spent more time on CR500's than KX500's and from what I remember they were more violent, and stronger off the bottom.

I guess I'm writing this to make sure it jives with your experiences?  I weigh about 40 pounds more than I did when I was racing, which surely has something to do with it.  These days, I prefer bottom/mid motors vs. mid/top. The rear shock and overall ergos feel really different also.  I have a 5.8 spring for intermediate MX, 220 pounds + gear. Sag is set correctly but the bike feels "chopperish" and doesn't turn as well as I was hoping.  Still some dialing to do there.

Thanks for any feedback!

Marty

Pics Link: (can't seem to get them to embed)
http://s1147.photobucket.com/albums/o559/h2yamyk/KX500/?action=view&amp;current=DSCN2917.jpg" target="_blank"><img src="http://i1147.photobucket.com/albums/o559/h2yamyk/KX500/DSCN2917.jpg" border="0" alt="'96 KX500 - condition when purchased

[wierdo]

I thought the same thing when i first got my kx500, i didn't know what all the hype was about, until i looked at the trench that i was leaving behind, too much revs and too much power  . then i started to listen to the guys on this forum about how to ride them properly ( upshifting early and getting into the highest gear as soon as possible) use the torque not the power. most importantly be smoooth everything seems slower when things are going smoooth.  just wait till you get some traction and then you'll see the difference. 

[greencannon]

if you were not impressed then its prob because the tire was trenching like others have stated.  even at high speeds on the gas
its spinning close to a 50ft stream of earth
Occasionaly im able to focus that brute power and get the rear tire to really hook under heavy throttle and the feel of the torque
 is almost mindblowing.
That big KX chassis makes big power feel a bit more tame than it really is sometimes, dont worry youll get a reality check when
you go to slowdown and realize you just came into that turn way too hot
 

 

[The Flyin Hawaiian]

It had been over 20 years since I had ridden a 500 of any type when I built my 04 KX250/500. I felt the same way as you did in regards to the power delivery. Ive raced enduros on mostly converted 250 mxrs over nearly 30 years with 2 years on a 88 KX500 here on the east coast. When I got back on the 500 it just never felt scary fast. I did notice the torque which is one of the reasons I like it so much. I also noticed the trench it was leaving behind! I tried a friends CRF450 out a few years back and that felt like it would be a handfull in the tight stuff! My 500 is so smooth and controlable in the tight woods! It hooks up well and just motors along. Its easier to ride than my 250! At first I felt slower on it because I wasnt on the pipe like the 250, then I noticed that the scenery was going by awfully fast with half of the effort. I changed my style to suit the 500 and ride it more like a 4 stroke. My wife loves it also and wants me to build her one!

[Hillclimb#42]

 I have Hillclimbed a 96 kx250 and a 97 500 for a some years now. The 500 was stock length and so was my 250 for the first few. Surprisingly, the 500 times were not always faster than the 250 times, and even when they were, it wasn't by much. A 500 seems alot faster because, for one its louder and pulls harder at times, but also spins alot harder at other times. Out on the trails and ridin for good times, I agree lugging the motor will hook it up and show you the difference quickly. I would disagree that the cr 500's are more explosive. they have no powervalve and have less power stock, but I believe this gives them more traction. the powercurve on a dyno has a big jump in power when a kx powervalve opens. That lends to its traction issues... or rut- making skills depending on how you look at it.

During a race / hillclimb / dragrace, the hook-up has alot to do with body position and bike set-up. When spinning too much, you really have to grow a set and scoot back on the seat, but be ready to get the weight off the wheel when going ( i.e. leaning forward or slipping the clutch). My worst bad habit is, I give the 500 too much respect, and ride the tank when I need to go fast. the ideal traction point is ............. The front wheel barely off the ground. Maybe two to three inches max, when you start using body english to carry the front wheel, while holding it wide open in second, then you are fast. to  go faster, its a matter of gearing and suspension (and tire) set-up. I wouldn't think of pulling 1st gear holeshot on the 500. The guy to beat in the 600cc class that I race has a worn out spot on his cr500, where the seat meets the back fender. he is also a master at keeping the front wheel light.

 The thing that I noticed about the 500 that surprised me, was that the 500 jumped and landed as well as the 250. I thought it would be like driving a streetbike around the woods, but it is really close to the same in that area. I would definately agree that my 250 turns much better than the 500. the 500 will chew up a whoop section though like no other. Now with the extensions on the 500, with some race mods and race gas, i would venture to say that it is the animal that everyone is talking about. I have had 4 runs up the hill on it this year and i would say 3 of those runs were too fast for a good healthy long life.