KX450F vs. KX500

[hughes]

My boy's 2004 Yamaha TTR-90 is going strong with no valve adjustments or top end failures.

i don't think that helps. the old style 4t's were very reliable, xr650's and stuff. i had a 200x that ran forever but that stuff don't count. its the new style 4t racing motors that have every part as small as possible to save weight, and pumped up passed the point of reliability in question.

I was just trying to add some humor.   

[don46]

honestly, it comes down to what you want to ride and what your willing to deal with, bottom line, they're all good, it comes down to personal preference. Admittedly a catastrophic failure whether 2 or 4 stroke would be expensive, reality is that catastrophic failures are pretty rare, and if its a new bike the manuf. usually takes care of it. As BDI said earlier, you have to do the PM, you do that and you have a pretty trouble free bike.

[bigbellybob]

As BDI said earlier, you have to do the PM, you do that and you have a pretty trouble free bike.

i don't remember him saying that. i do remember him saying

Titainium valves like to lose their heads after so many hours regardless of how well you maintain your bike and should be changed out as prevenitive maintenance like two stroke pistons.

and saying

I don't think that cleaning your air filter or changing your oil regularly can make any of us immune to these sorts of failures.

                                                   http://met-tech.com/motorsports.htm

[BDI]

I have a honda CRF450x and It is easily the best bike I have ever owned. The freedom this bike gives me is awsome, I can leave my house and as long as I can keep linking gas stations I can ride forever no two stroke oil needed. I try not to kill my bike with maintenance, I don't clean my filter every time I ride, I don't power wash the hell out of my bike every time I ride, I do keep My valves adjusted, I do keep my oil toped off and I change It when I think It's been in there long enough. I also live life on the rev limiter and I will be changing out my valves when I notice the bike wanting valve adjustments to frequently. Because I do my own valve adjustments hopefully I will see that train coming down the track, no matter what kind of bike you own you should always keep your ear on the rail.   

[bigbellybob]

i have a 07 yfz450 and it is easily one of the worst bikes i have ever owed. had to pull the cab 6 times just to get the thing so it would not die when you gave it the gas, this is new off the showroom floor. and when the time comes to pull the head i will be looking for a 2t to putt in it for the same price of rebuilding the head.

[don46]

  . Titainium valves like to lose their heads after so many hours regardless of how well you maintain your bike and should be changed out as prevenitive maintenance like two stroke pistons. 

Bigbellybob do you remember this statement, the one I was referring to?

You and others have had bad experiences with the 4t, thats to bad, I think they are good bikes and are alot of fun to ride, but at the end of the day it's to each his own. I find people either love them or hate them, I ride only KX's so I can't talk about other brands, but I'm sold on them. They have not cost me a dime, other than PM's, now having said that they'll probably both blow up tomorrow

[bigbellybob]

don46 yes i remember i just quoted it 2 posts ago. and that's my point i think it was $80 a valve, that's some costly PM's. i really hope your bikes don't blow up tomorrow. i was on the fence for some time and was really thinking of getting a new 4t but found that i couldn't afford to pay the payment and still pay for the PM's. the power that the manufacturers are getting from these new 4t's is unbelievable. 15 years ago no one would have believed you if you told them a 450 4t would put it to a 250 2t. i really believe that the 2t and the 4t have switched roles in the reliability department.

[Good]

I'd like to ride a 450 just to see the difference.

Actually HOW different is the 450 from the 250 2stroke?  Truly, does the 250 not compare powerwise?

I rode a 250 4 and it was weak, but haven't thrown a leg over a 450 yet...  I was very impressed with the rear shock on the bike at the time, though.  It was a Suzy from around '04 or '05.

If I had the money, KX500AF...  I'd even be happy with the ATK700...  dreams...

[don46]

In a drag race I don't think the 450 is faster than the 250 2t, the 4t puts the power to the ground better and has better low end torque, but if you can twist it and hold on the 2 t will climb with the 4t.

I'm not necessarily a 4 stroke guy, I have 4 2t and 3 4t and have bought a new 06 250 motor off ebay that I'm going to big bore, who knows maybe that will be the ticket, the chassis is great, I don't like the power delivery of the 250.

the other conclusion, nothing is cheap anymore, diesel fuel is $4.20 a gallon and probably more in other parts of the country, if you wan to play, you've got to pay.

[bigbellybob]

yea racing ant cheap. i think the 450 has a big advantage over the 250 2t. they have  more torque and that's why they put more to the ground and most make more peak hp too. but with the 2t getting back some of the cc advantage they are bridging the gap. the new ktm 144sx is a good example. it is not winning a lot but is very close.

http://www.motocrossactionmag.com/ME2/dirmod.asp?sid=&nm=&type=news&mod=News&mid=9A02E3B96F2A415ABC72CB5F516B4C10&tier=3&nid=350AB56EC8BB41F49929CD8E1737A06E

i think we could see a ktm 285sx next.

[kayx250]

I'd like to ride a 450 just to see the difference.

Actually HOW different is the 450 from the 250 2stroke?  Truly, does the 250 not compare powerwise?

I rode a 250 4 and it was weak.....

thats how I felt when I rode my first ever 4-stroke mx bike I was embarresed to tell the guy what I really thought and this was me coming off a 2001 kx125 thats had never been open even for a new piston!!...that thing was a turd...now I did ride a 07 kxf450 and it was a power house and like someone said I actually do believe my bike "could" technically win in a staigt out drag race(I actually put money on a drag race with him but he refused) on a track it would slaughter me but then again thats what they are designed for, winning races and thats it, not lasting 10 years on the same piston, or starting easier, and running cooler or what ever you guys are complaining about they are full out RACE BIKES

[Kev]

Hi guys, For four pages everybody has been stating facts, not opinions, and kayx250 hit the nail on the head. The new 4t's (KXF, CRF-R, YZF, RM-Z) are full on race machines. Technology on par with F-1 racing. Does anybody here care to imagine what the maint and repair costs are on a Honda F-1 engine? I know a lot of you guys are around my age (45) and raced in the seventies. Do you remember doing top ends after every race on your 2 smokes? If you didn't you weren't competitive. I don't recall thinking how cheap it was. Relativity gentlemen. 4 strokes are here and here to stay and 2 strokes will soon only be in museums. I am not a 4t cheerleader, I prefer 2t, that is why I ride the KX5 and that is why I was just discussing the KX 250 with Don46. However only a fool thinks that 2t's are going to make a come back just because of their maintenance costs. The EPA couldn't care less about the maintenance costs on racing motorcycles and they d*mn sure don't care about our leisure time hobby. 2t's might well be available in the future, but we all know that it will not be for retail. You will have to be a race team or you won't touch one. It has been a good 4 page read and everybody has stated the obvious and some not so obvious facts. So now lets all go and buy what we can afford, get lots of dirt/sand in our teeth, ride em til they break, fix em and get more dirt/sand in our teeth before the Gov takes it all away from us. Keep em roostin boys!!!   
Kev

[kayx250]

well I officially can vouch for the little debate here....4-stroke for the win.





I have a 2003 kx250 with a 2005 kx250 engine swapped in and I just bought a 2008 kx450f and the 450 wins hands down it handles better, pulls harder, hooks up better, breaks faster, I can ride a wheelie in 5th for like a full mile now becuase I have so much more control of the power and the best part it it makes me feel way more confident riding on it the one and only complaint so far is it is EXTREMELY loud

[Uzi9mm]

Fully indoctrinated.  Drinkin the Kool-aid.

[KXcam22]

Still liking it!  Now that I am more used to it I can use the advantages of the power delivery to go faster.  It's a stable platform that inspires mega confidence.  I can get one kick starts, hot or cold most times.  I am used to kicking the KX500 so this thing is like kicking over a vespa scooter. Stalling is the only major issue and I am down to about 1 per hour of riding.  In the same situations and terrain the KX500 would stall zero.  Frustrating, since this type of flameout stall sometimes takes a dozen kicks to restart - then you have to catch up and re-pass.  For really tight riding the KX is vastly superior - 4strokes just don't lug the same.  My KX brakes were excellent so no real improvement there. The real place that I find it superior to the KX500 is comming out of corners.  When the KX hits the powerband you get a fair bit of wheelspin (and excitement) just about the time you get to the acceleration bumps. This makes it diffficult to control while maintaining the acceleration (but it is also why we love 500's).  The 450 power allows me to use more throttle in the corner so my exit speed is much, much higher and then the different power delivery makes the acceleration bumps kind of vanish.  In a typical single track corner I can easily gain 10-20' on the exit on most people I am chasing.  I am still not a convert but becoming a big fan.  Cam.