KX450F vs. KX500

[Good]

No offence, but if you want less power, get a 250 and stroke it/mod it.  That'd be between a 250 and a 500 and might be the answer there.  Maybe also get a bigger rear tire.  Just like a car, the bigger the tire, the more traction.  Just thoughts.

[500GUY]

KX or CR 500AF are the real program, half the reason the 4 strokes get better traction is modern geometry the other half is simply smoother power pulse. But put a flywheel weight on a 500 AF and they are awesome trail bikes. Get those new 4 stokes smoken hot in the trails and when ya stall them you be kicking it all day.

[kxraptor]

I switch riding between a kx500 and a yz450f.Its true the 4strokes do like to stall in some inconvenient spots , but a flywheel weight seemed to cure that.I seem to use the brakes a hell of a lot more with the KX.The newer suspension is a real plus on the YZ,but I'm gonna put a Racetech setup in the KX and hopefully it matches up well with the Yamaha.

[500GUY]

I seem to use the brakes a hell of a lot more with the KX.

That's one major point I forgot to mention, Engine braking on down hill trails are a bonus on the 4 strokes. But I hate the popping and farting.

[Texas Champ.]

I race the Houston area, You wouldn't believe the number of racers that have "Had It" with 4 strokes....You'r first comprehensive over haul will cost you 1/2 of what the bikes original cost is and this will happen from 35 to 70 hrs. on the engine . I'm not sure the 4 stroke is going to work well . many families can't afford the higher 4 stk. cost as opposed to what they used to pay to run a 2 stk....If you fall they dont restart well , finicky jetting is very sensitive to temp. and altiutde changes...and the Fuel injected Suzi's are a constant maintenance item..(maybe down the line they'll get better)..The AMA has restructured the classes to benifit the 2 stk this year...The new YZ 250 Has a 4 stk like powerband to help lure riders back...2 Strokes aren't dead yet...with the encomomy in a pinch, look for 2 strokes to sell very well this year...and of course manufactures will notice ..they don't like to build bikes that won't sell.....Kerry

[previous quote]"I seem to use the brakes a hell of a lot more with the KX -500"

Well coasting is a bad habit in MX..The K5 shoud be ran hard to the corner then brake hard,1 click down on the shifter, turn and feed em' a constant roost diet...they dont manufacture a good enough chest protector and enough tear-offs to stay behind a KX-500 very long...So if they are behind you...Give em' a taste.....Could we start you off with an appitizer today???........Kerry   

[GDubb]

That is exactly what has kept me out of the 4 choke market. My girlfriend is getting ready to buy her first bike ever (after I took her for a ride on my K5 she was hooked!).  The salesmen at the local Kawi dealership and at the Honda dealership were both pushing the new fourstrokes. I told them they had got to be kidding if they thought I was gonna buy a bike that was gonna cost half of what I paid for it just to rebuild it when the time came. Honda didnt have anything to offer except a CR85 for a 2 stroke, and Kawi was pushing the KLX140L.  But she is a smart cookie, and is set on the KX100.

One good thing about the fourstroke 450f and 250f is that in the future there should be plenty of rolling chasis' on the market for pretty cheap and if I can ever afford it, it will be K5 swap city for me.


-G

[Uzi9mm]

  My buddy recently got a CRF450X.  I guess the valves must be adjusted at certain intervals.  The first adjustment cost him about 500$.  Then the bike was makin some funny noises, it cost him 400$ and change.  Somthing about the compression release.  He was looking at aftermarket exhausts too.  But decided against it.  An after market Pro-Circuit setup is around 7 or 800$.  NO Thanks, I stay with the KX500!   

[Texas Champ.]

The valves are a constant adjustment problem. The compression release works of of the exaust valves and has to be adjusted as well then you've got the cam chain , even if you have an auto adjuster..you still have to check it. The cost of a 4 stk. exaust will get your 2 stk a pipe ,and suspension set up nice, unbreakable levers and aftermarket replacement reeds....lay them over in a corner during a race and see which one starts first...the NGK plug for a CR450f  msrp right at $16.00 ......Kerry

[BDI]

I just had to put a head on a yamaha yfz 450. Unloaded head $425.00, valves $80.00 X 5, cams $300.00, springs $1.25 X5 . I was able to use the the retainers and seats. These are the best prices I could find on line and and did not include piston, cylinder and gaskets this was for an 04 quad.I still feal bad for fixing the bike for the guy I tried to talk him in to parting it out and buying a new one.

[don46]

I race the Houston area, You wouldn't believe the number of racers that have "Had It" with 4 strokes....You'r first comprehensive over haul will cost you 1/2 of what the bikes original cost is and this will happen from 35 to 70 hrs. on the engine . I'm not sure the 4 stroke is going to work well . many families can't afford the higher 4 stk. cost as opposed to what they used to pay to run a 2 stk....If you fall they dont restart well , finicky jetting is very sensitive to temp. and altiutde changes...and the Fuel injected Suzi's are a constant maintenance item..(maybe down the line they'll get better)..The AMA has restructured the classes to benifit the 2 stk this year...The new YZ 250 Has a 4 stk like powerband to help lure riders back...2 Strokes aren't dead yet...with the encomomy in a pinch, look for 2 strokes to sell very well this year...and of course manufactures will notice ..they don't like to build bikes that won't sell.....Kerry

 

We've had riders go back as well, but then most aren't the most mechanically apt anyways and it wouldn't matter whether they rode 2 or 4 stroke. I don't know where you got the 35-70 hrs. number or the 1/2 the cost of new, but I would have to call BULL, I've had 5 250f's and 1 450f and haven't had problem 1 on either, these are Race/Practice bikes. Oil and air filters are changed diligently, valves are checked frequently, rarely have I had to adjust them, the 450 is on it's second season, I've cleaned the scavenger screen, changed the piston, checked the valves (they haven't moved since new) it runs like a watch. In my opinion, most people that have problems can be traced back to them, and it doesn't matter the brand. Oil and air are number one, then stay off the rev limiter all the time, can't tell you how many times I've listened to some of the local racers riding them like a 125, hammering the rev limiter, and low and behold they are the ones with the crappy bike that blows up, and right next to them is the same brand with no troubles.

Admittedly they are more labor intensive and cost more if they do blow up, but out on the track a 250 2t doesn't stand a chance, if they did you'd see more at the races. I read an article in DR today, there was a kid that was trying to qualify a 250 RM, couldn't make it, then went out on a 450he'd never been on before and beat his lap times by 7 sec. If a person was only doing cross country or trail rideing a 250 2t would be a fine play bike, but if you want serious MX you have to go 4t.

[Texas Champ.]

 Don ; The post prior to yours replace the head...over $1000.00 , no piston, rod, crank, and labor.  Don I didn't register on this forum to come on here and lie....If I don't know,I don't reply.
 The people who I know that have had these problems change there oil often ( some every ride ! ) . It maybe that it's hotter here than where you live ( left blank-no entry)  Your quite fortunate that you can change a piston or crank. most mx Dad's can't do that. , so they have to pay a shop to do the work and it adds up.
 2 stks. are competitive. Mike Clement ( 6 time Vet. World Champion ) does it on a 2 stroke , the guys trying to stay up with him are on the limiter and constantly winging the clutch.....km

[don46]

I'm not syaing your lying, I'm trying to understand, by your account, every 35-70 hrs you must shell out $3000-3500, lets be real, if that was the case the manuf. wouldn't sell 4 strokes, there would be a revolt. Sorry to say, I still believe it goes back to the person riding/maintaining the bike. On the MX track a 2t can be competitive in a very few circumstances, very few, for example a very tacky track with an abundance of ruts, on a hard slick track no way. Sadly, look at the starting line at the Supercross races or last year at the nationals, if a 2t  was good you'd see more of them on the starting gate. If everybody went back to 2t , I'd be right in line, but at this time to be competitive you've got to have a 4t, bottom line. On the KXf there is no adjustment on the compression release, the cam chain is automatic.

Yes there are things that are more of a pain on the 4t, you won't get any disagreement from me on those points. I'm saying no way that kinda dough for a rebuild and that the 2t is not competitive with the 4t on the MX track. You seem to believe that without a doubt the 4t is going to blow at 35-70 hrs and when it does it will totally destroy the motor, no sorry not seeing it, i've seen busted pistons that did no damage to the motor other than the piston. But hey, believe what you may.

[bigbellybob]

i've seen busted pistons that did no damage to the motor other than the piston.

how much did the new piston cost? where did the peaces of the piston go? how did that not damage other things in the motor? how can the rod go up and down with no piston and not damage something? this is hard to believe.

as the rules change the 2t will become more competitive. the 4t has just had to grate of an advantage. yes a motor that is babied will last longer than one that is hammered on. but racing is the hardest thing you can do to a bike. the 4t is definitely more expensive, they cost more to buy and cost more to maintain and really cost more to rebuild.

[KXcam22]

Easy on the words there boys. This is all very interresting.  I am a new 4-stroke owner and I am not worried.  I recognize that this bike will not take neglect like my K5, but then I am a fine mechanic and have never neglected a bike yet.  I expect at least 100 hrs or more between valve adjustments.  Many get this. If I was back racing it would be less.  About the only difference between my K5 routine is the more frequent oil changes but even that is blown a bit out of proportion by some.  From what I read some change their oil every ride. My manual suggests 15 hours - I am going to hedge my bets by going 15 hours but running good synthetic. I did have to add an hour meter, which is probably a good thing to have on any bike. Keep the air filter clean and I have no worries.

I can understand that the new 4-strokes aren't for everybody.  I have only ridden the bike a few time but already I can tell (other than the newer ergos and suspension) that the 4-stroke power characteristics allow me to put more tractible power the ground (which is the part that counts) that anything I have been on.  I think a good example to look at is supercross; tight tracks make me think that light bike weight would be king (as in 2-stroke) but even the privateers are riding 4-strokes for the acceleration/traction factor to clear the jumps with short in-runs.  I am sure reapir costs can be astronomical for a grenaded 450 but the same goes for a 2-stroke if you snap a rod and whindmill it through the cases.  It is my opinion that for someone who must take his dirt bike to the dealer for maintenance, then a 4-stroke is not for them.  I was eavesdropping at my local dealer, and he quoted a guy $400 for brake bleeding and some other misc work - and he wasn't out of line - just the number of hours required at their shop rate.  I also notice that many dealers steer customers onto these bikes knowing that they can't maintain them properly. On the flip side I have also seen dealers recommending lawnmower quality 2-cycle oil to owners of new high performance 2-strokes (KX85's), both somewhat underhanded practises.

I have to support Don on the shattered piston thing.  I have had that happen to me a number of times where it caused no other damage.  I once blew a cam ball-bearing on a 4-stroke 500, took off the sump and managed to reassemble the broken bearing cage parts until I had found them all, replaced the bearing and off to the races - no other damage (yea I was lucky).

I know everyone has opinions and has "heard" about some ugly costs and rebuilds but I like to talk directly to the guys who ride em and race em for some real evidence.  So far I think this bike is going to be great and last a long time, but who knows.  Maybe in a few years I will be looking for a K5 engine to shoehorn in there while my wife plants flowers in whats left of the 450 engine.  But for now I am going to wheelie away with a grin. Cam.

[puffy]

I agree with alot that is being said .But 40 to 70 hours until a rebuild is no way true. But 3000 grand for just parts to rebuild a 4 stroke is a minimum.Every one I know says if you can do it for that your lucky.