Long term 2004 KX250F report

[Aaron_Silidker]

Just thought I should post this here since not many people read the KXF/RMZ forums and I think this pertains to anyone who owns a four stroke MX bike.

As everyone knows, the 2004 KXF/RMZ is touted as one of the least reliable small bore MX bikes made. I am posting this to show that they are the opposite of that when taken care of.

I bought my bike used in august 2004. Had no problems with the bike. In june 2005 I decided to do a top end, and due to my stupidity wayyy overtorquing the cam cap bolts I put a different used head on. At the time when the head was off I replaced the valves with new stock ones just so I knew they were ok. I also had a very good valve job done on the head on a Serdi machine to make sure the seats were concentric to the guides.

Last fall after the bike was 2 years old, the crank big end bearing siezed. No big deal, happens to many bikes I own and I consider it a normal wear part. I replaced the crank, crank bearings, and did another top end. The valves had not moved at this point and I was very impressed considering I really don't baby the bike.

Today I checked the valves again and low and behold after being in the bike for well over a year, 3 top ends total, numerous oil changes, riding in all different types of sand, mud, dry dusty weather, etc, they hadn't moved at all.

To this day I have no clue how people managed to blow these things up so much...guess they didn't know how to take care of them and not over rev them constantly.

For what it's worth I am a slower B class MXer and ride pretty agressively....agressively enough to ruin a frame in a crash I had when I first bought the bike.

Moral of the story, whatever you get has the potential to be reliable. Keep on top of the basic maitanence, don't ignore signs your bike needs attention (valve clearance tight!) and when you do replace the first set of valves that get beat up by the stock valve job, get a good valve job done on the seats by a very experienced machine shop. The guy who did mine pretty much guaranteed me that the reason these valves go to crap so fast is the fact that the stock valve job on anything (car, bike, etc) sucks and the seats arent concentric to the stem so the valve head has a bending moment on it.

[punkrock MX]

ruin a frame in the crash? lol..unless u cased some hugeee jump or happened to land on a rock i doubt u could really bust the frame up..most pros cant even do that. pro sx riders go through frames alot but i dont think anyone on here rides hard enough to do that

i guess you're one of the lucky few thats had good luck with the rmz..most people dont

[Aaron_Silidker]

I crashed, the steering stop broke off and the lower clamp broke and the fork smashed into the frame and crushed a tube. New frame from ebay and I was set!

[barch88]

People need to take care of their stuff better. I see so many bikes that just look horrid because the maintenance, and then they bash the brands because they didn't take care of it and it broke.

[Bobarino91]

uh, three top ends, a new head, one crankshaft and bearing, and a valve job in two years and that's reliable? you replaced just about everything but the case and cylinder. i'd hate to see what you condsider to be unreliable.

Bobby

[kyleyz]

my 02 has only had one top end! no break downs either....

[Motocross26]

uh, three top ends, a new head, one crankshaft and bearing, and a valve job in two years and that's reliable? you replaced just about everything but the case and cylinder. i'd hate to see what you condsider to be unreliable.

Bobby

[RideRaceLive123]

Yeah I agree with you with a crank being a normal wear part..on a 2-stroke. Because on my 80 a crank would only last like 5 rides but that thing was a unreliable piece of crap.

But no way on a 4-stroke, because they have oil being sprayed directly on the crank.

BTW, how much hours did you have on your KXF?

[bigbluerider4life]

like someone has already stated all that stuff u did in only 2 years and thats reliable?

u shouldn't ever have any problem with fourstrokes other than normal maintnence and wear, ( what you stated isnt normal)

o yeah and suzuki and kawasaki do suck, it isnt cuz no maintnence etc.

they just suck

yamaha forever! ESPECIALLY THE 250F'S

[AHerm87]

Wow. I'll bet all those part replacements were expensive. Are Kawi/Suzuki 2 strokes known as unreliable? Or is it just 4 strokes? A friend of mine has a '99 KX125 with good compression on the original rings and piston. He never did any type of racing with it, but he does crank it and let it warm up for 5 minutes before riding. Do MX/SX guys just wear their bikes out faster?

Another friend has a 2004 CRF250X that he rides harescrambles/enduros with. He's never had any problems with valves/pistons/rings. He is meticulous about maintenance and goes pretty easy on the bike. Neither of my friends have any aftermarket mods on their bikes except eliminating the stock lean jetting.

All I hear (on this site) is about problems with modern liquid-cooled racing 4-strokes, particularly with the valves. So I'm wondering, is the problem the manufacturers, the riders riding the bikes hard, aftermarket parts, lack of maintenance, or some of all of it?

I'd like to get a CRF250/450X but all these horror stories make me wonder if I'd be buying a money pit. Sorry If my post is unorganized, my thoughts usually are.

[Aaron_Silidker]

You guys are the reason they blow up! Top ends are preventative maitanence. I did the valves so they were a known to me, the head was my fault, not kawasakis. I just torqued down the cam caps without looking at any specs.

A crank is a normal wear item on any bike, 4 or two stroke. These are ultra high performance machines and they wear out. I got about 6 months on my 125 cranks and 2 months on a top end.

If you guys think a slipper piston (the little teeny pistons that are in these bikes) can last more than 60 hours you are nuts.

I guess you guys all want bikes that you never have to take the engine apart and just ride it forever. Get a freakin XR if that is what you want. The fact remains this bike has only let me down ONCE and that is when the crank was old and I knew it needed to be replaced.

Anyhow, I consider unreliable to be a bike that breaks unexpectedly. This bike has never done that. I knew the crank was iffy when it siezed last fall.

BigBlue, you state nothing should be a problem with normal maitanence...what do you consider normal, just oil changes? There is a reason people replace top ends, a reason you replace the valves when they start to wear, a reason why you replace cranks after their service life is up, it is called preventative maitanence and it keeps your bike from breaking when you least expect it.

Oh well, I tried....guess people will never be realistic about their bikes.

[MetalMan1729]

All the manufactures make good bikes, people post about the problems they have with their bikes. People don't start threads just to say their bike has not blown up. The vast majority of people with fourstrokes do not have major problems with them. For you guys that say kxf/rmz sucks have you owned one? Have you experienced first hand that it is not reliable? I know some of you have had problems with them but all the 250f's need maintenace and work. Personally I have 65 hours of hard riding on my '05, stock valves, no problems, just regular maintenance. And allot of that riding was top speed 5 gear in the desert, and riding like that is hard on the valvetrain.

[MetalMan1729]

Part of the regular maintenace was I replaced the piston once and shimmed the valves once, and they were not even out of spec, they were just slightly tight.

[Bill_P]

uh, three top ends, a new head, one crankshaft and bearing, and a valve job in two years and that's reliable? you replaced just about everything but the case and cylinder. i'd hate to see what you condsider to be unreliable.

Bobby

That's exactly what I was thinking. If that's reliable, I need to find a new sport.

[mxkid416]

I've had my 05 for a year, and the valves haven't moved once and not a thing has gone wrong with it.

+1 to what Aaron_Silidker said, the reason alot of them are blowing up is because people don't replace stuff as it wears, I see nothing out of the ordinary that he replaced. I don't ride as much as I used to, but only 125, I would put a new top end in at least once a month, new clutch every other month and crank and bearings at least once a year, Its all preventative maintence. Things wear out. They need to be replaced.

[Aaron_Silidker]

Oh yea forgot to add that I had to replace my clutch because it became worn out...guess my KXF is a total POS because wear parts have to be replaced. Chain and sprockets had to be replaced once also! What a POS!!!

[barch88]

Oh yea forgot to add that I had to replace my clutch because it became worn out...guess my KXF is a total POS because wear parts have to be replaced. Chain and sprockets had to be replaced once also! What a POS!!!

You're parts seem to wear out a lot faster than most peoples bikes though. I know people with stock older YZF's that ride them HARD and they still run solid, valves never out of spec, etc...

[punkrock MX]

i dont understand why more people dont ride 250 2-strokes..they have torque and are REALLY reliable..i think 125 2-strokes are reliable but the 250 2-t seems to be the perfect balance of power and weight..

once u get used to them its like you're riding anything else..

[723onYZ250f]

just one of my many RMZ/KXF friends: brand new 06 blew up in 30 hrs with proper maintanence and everything and then blew up 4 more in just over a month riding basically everyday. he rode my yami 250f alot when his broke. never got those problems and the top end was well over a year with us bothing riding it alot.

[rmxtgh]

most of the 4 strokes are very reliable bikes.....you're better of with a 450 even if you are a slow rider cuz the 250fs are taxed more by revving etc....the RMZ and kxf did have issues with overheating cuz the radiators were not big enough to keep the bike cool.....crf 250's i've heard have a tendency to grenade the valvetrains.......yamaha's i've never heard of any bad things/recurring issues...i've got an 01 426f thats been perfect for me although i haven't ridden it much the last two years cuz last year i broke my arm last year and this year some assclown landed on me.....so i've been sticking to the woods on my RMX250 which has been super reliable.....the yamahas i think have been so good because they have plenty of oil capacity...all i've ever heard or seen is change the oil regularly and you'll have no problems.....my guess is aaron s. is a much better rider than most people on here and thats why his bike needs more maintenance than most believe is normal.....a low level C rider or slower is much easier on a bike than a fast B or A rider....