'02 YZ426 piston question....

I've had my bike for almost a year now and have put about 20+ hours in at the track. I used to have a 2 stroke 125 and I had to replace the top end way too often. My question is do I wate till my top end blows (loses compression) like on the 125 or should I go ahead and change the piston before I begin to have problems? Also I don't really know how much longer the pistons last in these things. Any advice would be greatly appreciated. Thanks guys :banghead:

Don't wait for the motor to blow, it will be very expensive that way. Bottom end including the piston usually aren't the wear items if the oil and air filter are kept clean. Bottom end usually requires bearings, rings and honing. Valve train maintenance is the main thing with a four stroke. Valves, valve springs, timing chain and a valve job will eventually need to be done.

Do a leak down test. Then visually inspect the top end, maybe even have the head reconditioned for piece of mind. These motors can and will last forever if properly maintained.

It's running great and idles wel. I've checked the valve clearances and timing recently and it was all spot on. It will occasionally die if it sits runnin for a while when it's hot. What is a leak down test? And if it's running okay do I really need to worry about these things? I'm still a virgin to all this :banghead:

A leak down test is a compression test. It'll tell you if your rings or valvetrain have loosened up.

It's up to you if you want to worry about it or not. These are the most reliable thumpers, but their not bulletproof. Do you know the previous owner and his maintenence routine? The biggest problem these bikes have is poor maintenence by the owner.

He treated it very well. Routine Air filter cleaning and oil changing.

If you trust him then dont worry about it.

The engine will let you know when its time to freshen up. The 02's didnt have many weak points.

My 01 WR426 has around 210 hours and 3705 miles on the stock motor with only two valve checks. Both times valves were well within specs. Many of those hours are from dez races. The bike runs like a clock.

I always change the oil every ride or two and clean the air filter before every ride. The bike runs better then the day I bought it.

my yz426 was perfect even after 2 race seasons had it checked before i sold it and was perfect

oil filter and air filter all the time

Man.....hearing stuff like that makes me all warm and fuzzy on the inside. When I first rode my new bike, I thought it was the greatest thing ever made by man. I thought it was the perfect blending of man and machine. When I go around the track I feel a flow, a smoothness I've never felt on any other bike. It's a little heavy, but I weigh around 225 so I can still toss it around like a CRF. My only fear was that it was going to be as big of a hassle as my 125 2-stroke. From what I've heard I'm going to have a great time while owning this bike. Now if I can only find a tire that won't get ripped to shreds by mixture of torque and hard dirt at my track......long live the YZF!! :banghead:

Man.....hearing stuff like that makes me all warm and fuzzy on the inside. When I first rode my new bike, I thought it was the greatest thing ever made by man. I thought it was the perfect blending of man and machine. When I go around the track I feel a flow, a smoothness I've never felt on any other bike. It's a little heavy, but I weigh around 225 so I can still toss it around like a CRF. My only fear was that it was going to be as big of a hassle as my 125 2-stroke. From what I've heard I'm going to have a great time while owning this bike. Now if I can only find a tire that won't get ripped to shreds by mixture of torque and hard dirt at my track......long live the YZF!! :banghead:

Rule of thumb weigh half as much as your bikes CC's. Kidding. 225 on a 125!!! Damm I would give the 125 props. Your gonna love the thumper.

For tires I always recommend the Maxxis IT rear and a Dunlop 756 front on these bikes. If your track riding then go with a Dunlop 756 for the rear tire as well. Tire selection depends on the terrain. Which is different for all of us.

I still believe the Maxxis IT rear is hall of fame tire. Great price and fantastic wear. The Dunlop 756 up front is killer as well.

Rule of thumb weigh half as much as your bikes CC's. Kidding. 225 on a 125!!! Damm I would give the 125 props. Your gonna love the thumper.

For tires I always recommend the Maxxis IT rear and a Dunlop 756 front on these bikes. If your track riding then go with a Dunlop 756 for the rear tire as well. Tire selection depends on the terrain. Which is different for all of us.

I still believe the Maxxis IT rear is hall of fame tire. Great price and fantastic wear. The Dunlop 756 up front is killer as well.

http://i4.photobucket.com/albums/y146/Kizzle426/DirtBike006.jpg :banghead:

Just put it on a couple of days ago. Also, I didn't used to weigh as much. When I was racing the 125 I weighed about 175 but didn't have any muscle. I forgot to mention I'm 19 and 6' 3" and Have a bit of muscle, So I'm a little heavier now. I've had the bike since the end of January and I love it. Here's a pic (just had to)....

http://i4.photobucket.com/albums/y146/Kizzle426/20516aab.jpg

http://i4.photobucket.com/albums/y146/Kizzle426/6119f096.jpg

Yes I race it, I just recently put the stock sidepanels on and took the number off the front number plate. The guy who had it before me had #4 all over it like a Charmichael wanna be. When I race now I just put an 11 on in electrical tape. Anyway, I'm done now. :banghead:

Man.....hearing stuff like that makes me all warm and fuzzy on the inside. When I first rode my new bike, I thought it was the greatest thing ever made by man. I thought it was the perfect blending of man and machine. When I go around the track I feel a flow, a smoothness I've never felt on any other bike. It's a little heavy, but I weigh around 225 so I can still toss it around like a CRF. My only fear was that it was going to be as big of a hassle as my 125 2-stroke. From what I've heard I'm going to have a great time while owning this bike. Now if I can only find a tire that won't get ripped to shreds by mixture of torque and hard dirt at my track......long live the YZF!! :banghead:

the word is maxxis tires

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