Are the 426f/450f realiable or high maintenace machines

I've been looking at used 426f and 450f and was wondering how reliable these bikes are and wheather or not they require a lot of maintenance. I heard stories of anything from gas and go to major valve problems, leaky fork seals, and constant maintenance. My preference is low maintenance and reliability.

Thanks in Advance,


They are reliable but do require maintenance. I have had mine for about a year and have tried to stick to the service intervals as close as possible. If you are planning on just putting gas in it and going without maintaining it you are going to have problems. The best thing to do is go on ebay a purchase a service manual on CD. They are selling them for about a buck.

Yes and yes. They are very reliable, but very high maintenance as compared to something like an XR. If you want to do nothing but put gas and oil in it, then buy an XR. If you want a solid "race bike" then get a YZF.

They are very reliable, but very high maintenance as compared to something like an XR.
I've had Xr's before, what are you saying is the basic difference in maintenance between the two? Anything major other than more frequent valve adjustments, for example?

My best advice is get both manuals and take a look at the recommended service intervals. In general; The YZF will need more frequent valve checks and oil changes. The top end on the XR will probably last longer (in hours) than the YZF as well, given similar maintenance; although for a race bike the YZF top ends last a very long time. Also the YZF may be a bit more sensitive to weather conditions in relation to carburetor adjustments. I would expect the YZF to be much harder on sprockets, chains and tires given the difference in power. If you ride tight (eastern) trails where it's warm then the YZF may boil over if you're going too slow, the air cooled XR will not.

I assume you are trail riding, otherwise non-race 4-strokes would not be considered. That said, if you MX then you'll want everything in tip top shape for every ride, in which case you'll likely find yourself doing and hour or two of maintenance between most rides (checking nuts/bolts, cleaning and lubing various things, adjusting various things, etc...). But this would be the same for both YZF and XR, if you were crazy enough to MX an XR. Given what these bikes were intended to do, they are very reliable. But they are intended to be race bikes and the recommended maintenance schedule reflects that. The XR has the reputation of running forever with nothing more than gas, oil and air filter maintenance.

So far I've been riding (trails) and doing maintenance on my YZ the same as my DRZ and in the past, my XR. As with anything I would think, the more high performance, the more care required. But for my style of riding (non-competitive) the hour or two before each trip would not be nessesary.

My 02 426 has been extremely reliable, regular oil and filter changes, I keep the air filter clean and lube where needed. I ride a little MX but mostly woods and trails. I have been extremely pleased with the bike. I'm old fat and slow so this will probably be the last bike (in this class) that I buy.


I'm still riding my 00 yzf426. I've put clutch plates and other minor maintenace things. No major problems! :cry:

My boy races B-class MX on our 2004 YZ250F and YZ450F every possible weekend. When not racing he's practicing. He rides them hard. I recently did a complete topend/head service on the 250F, but after pulling it down and inspecting it, it probably could have gone awhile longer. I bought them new in the fall of 2003. We dump the oil and service the air filters before each outing and change the oil filter every 3rd as a rule, but modify that based on track/dirt/weather conditions and number of motos/days in an event. The 450F has never been apart and still hauls like the day it was built. Both machines are still running the original clutch plates. They are rock-solid, awesome machines.

they're bulletproof

I've had Xr's before, what are you saying is the basic difference in maintenance between the two? Anything major other than more frequent valve adjustments, for example?

Keep your air filter clean and change the oil every 8-15 hours, and check your valves once a year and you'll be fine.

They are reliable, high maintenance machine. Take good care and they will last and perform well.

Id have to say this bike i have has impressed me. I dont kill it because i dont race it BUT im in no way nice to her. I may rev her to high sometimes because ive been a 2smoker for many years :cry: But do the oil as recomended and filters and the like and youll be very happy with it. :cry::cry::cry: I just checked my valve clearances for the first time , they are right on the $$, so im ridin 2marrow. :devil::devil::cry: AND it rained today . :D:D

My 426 has been very good to me so far. Aside from valve adjustments (mostly from installing the 450 cam) I haven't had to do any "extra" maintenance. Change the oil often, keep the air filter clean, keep your valves in spec and you'll be happy.

Compared with other MX four strokes, the big YZF's are about as difficult to maintain as a sundial. Get a good Stainless oil filter, clean it with every oil change at around 10 hour intervals, keep the air filter clean at about the same interval, and all the other normal dirt bike lube and adjust stuff.

You'll probably need to adjust 2-3 valves within 20 hours on a brand new bike, or after a valve job, after which it may go for 2 or even 3 years without needing a valve adjustment. No, I'm not kidding. At some point, it will turn up with a couple of valves below clearance. Correcting them will last a while, and then one day it will suddenly have a couple of intakes at 0. You'll adjust them and 2-4 weeks later it'll be like that again, and you'll know it's time for a valve job. You'll have so many hours on the engine by then that you either won't believe it, or you will have lost track.

The '00 426 was built with Stainless valves, and their top ends last even longer. These are high performance engines, and they get run hard, so things fail occasionally. But NOT very often at all.

The 426's will break or wear transmission gears to the point of popping out of gear. The 450 has done this, but not as much.

The '00 had a balancer shaft drive gear that is held in place with a taper and a key. These work loose once in a while and rattle. New key fixes it.

The earlier 426 big end was weaker than the later ones, and I have heard (never seen) of them breaking.

The timing chains can wear the sprocket off the crank and or skip time with the possiblity of a valve striking the piston if not replaced once a year or two.

That's about it. I listed these "known issues" only to admit that they aren't perfect, but I can't stress enough how rare a failure of any kind is with the big blue bikes. There are cars on the road today that aren't as dependable. :cry:

my 426 was/is bulletproof. Of course like the others have said you must maintain them.....this is a RACE bike. I changed the oil every other ride and cleaned the oil filter ever other oil change. I cleaned the air filter every other ride and I checked the valves every 3 months or so.....although I only had to reshim them when I did the 450 cam mod.

I had NO failures of any kind after over two years of riding MX ....and we ride alot! I never had any transmission problems and or engine problems. Leaking fork seals are not bike specific...that happens with all dirt bikes after they wear. Fork seals, brakes, tires, oil changes etc will be fairly consistent among bikes and manufacturers.

The YZF's are very reliable and durable.

my 426 was/is bulletproof.

The YZF's are very reliable and durable.

yes they are, but when they break, they do it with pinache.

for example; instead of 3rd gear slipping out of gear, you may lose all use of 3rd gear.

or maybe you shred half of the teeth off of one of the 4th gearwheels.

my personal favorite is the straight key breaking the keyway off the crank (pre-01 only).

my 426 has not been bulletproof, but i ride it like a 125.

I've been very happy with my 2000 YZ426 and have had no major issues. Just keep up with regular maintenance items and you'll be fine.

I ride a 00 426 and ride 90% track, with regular maintenance, consistent oil changes, and very minor fixings, i have had no problems........ and she runs like a raped ape! :)

I love my 426. Change the oil and clean the air cleaner regularly. Keep up on the basic stuff. It really depends on how you ride it. :)

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