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Deepseadan

2002 YZ 426 about to purchase

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I'm just about to purchase a 2002 YZ 426 from my brother. I've been riding for 23 years, everything from 85 CR 500's to my latest bike, a street legal XR 400. Don't get me wrong, I love my XR and it's great for trails and i still plan on keeping it, but now that my son wants to go to the desert I would like something thats lighter with better suspension and power. I'm hoping for better hill climbing and less bouncing over the whoops. Now back to the 426. I know the history, it's been babied and is in near perfect condition. He's only selling it because he just bought a KTM 500 EXC. Are there any issues with the 2002 model or anything hidden that I should know other than the starting process. How does it compare to some of the new motorcross bikes. I'm getting it for $1000.

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I think the main thing with the early Yamaha race 4-strokes was relying on splash lubrication of the rod bearing and they would lock up. The yfz450 quad had the same issue till they addressed the problem.

I'm currently parting a 426 that had this happen and bought a quad that did it back in 08

In each case the machine wasn't mine when it locked so I can't say what oil and long it was between changes, etc. I would think if you run a synthetic oil and change it often you would be fine.

Rob

Edited by 02YZ85

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For a $1000 id buy 2 of them. :thumbsup: only had my 2001 for a few month but I love the bike,the suspension is soft compared to 450's,power down low is great.I find the filter dosen't get plugged up every ride and actually stays clean a long time.They are heavy bike but probably not as heay as the xr400.You need to check the oil filter drain bolt as they strip fairly easy and not sure about the 02's but I find the clutch on the 01 very grabby during first start after that its great.For the price and it runs I would jump on it,but the price of bikes here is much higher then most of the states.

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At $1000 and you know how it has been taken care of it is a steal in CA. i paid 1800 for my 2000 a year ago (still had original plastics and graphics on it, recent engine work).

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Yeah, it's nice to know where the bikes you buy come from. My brother is a finatic about oil, coolant, and other maintenance. He also has the oil / frame block off kit with sight glass on the case, changed out a bunch of parts to carbon fiber and countless other parts including almost new mx51 tires. The best thing is I'm trading my Yugoslavian sks and a little cash to equal $1000. Of course he's giving me a heak of a deal and he is a great guy. I can't wait. So you guys recommend synthetic oil?

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Edited by Deepseadan

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sounds like the wet sump conversion,if so change the oil more frequently than normal.

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that looks like a great bike for the price.. especially coming from a family member..

knowing the history is priceless, you hear too many stories these days of people buying old bikes off craigslist that lock up after a couple rides

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Im not familiar with the oil block off kit on these bikes. What is it exactly?

It's a kit that blocks the frame from being a oil reservoir and the oil is kep in the motor. It saves weight by using less oil, but you change the oil more often. Not my choice, but I will just have to change the oil more often.

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That would be the reason I would pass on the bike entirely, unless the owner could either provide you the parts to change it back with, or do it for you. I would not own one with the wet sump kit.

Also the splash lube information is inaccurate. YZF's have all always had a pressure fed rod bearing. The modification done to the Quad engines was to add a oil spray nozzle to the system to direct oil against the bottom of the piston crown to cool it, which helps the wrist pin avoid galling in the piston from excesses of heat, not a lack of oil. This was introduced first in the '06 YZ450 motorcycle engines, then two years later in the quads. The bikes never really had any trouble with it.

Otherwise, the 426 is a fine desert bike. The front suspension isn't much beyond a 6 out of 10, and it's a bit heavy, but it probably considerably lighter than the XR, handles better, and has a lot more power. Very, very reliable, too.

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Why is the oil block off kit bad? Lack of lubrication or just because of more frequent oil changes? Just wondering before I buy it.

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grayracer thanks for taking the time to explain how i was wrong above. I would rather be corrected than continue to tell it wrong. Do you know why the issue with the seized rods? The quad i bought had it happen twice. The second time is when the owner got frustrated and I bought it for cheap. The 426 I was told was idling when the rod locked up

deepseadan, if you end up going with the bike and your bro doesn't have the lines for the frame, I have them.

Rob

Edited by 02YZ85

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Why is the oil block off kit bad? Lack of lubrication or just because of more frequent oil changes? Just wondering before I buy it.

Ah ok, i thought it was the wet sump kit but i wasnt sure. The oil block off kit is bad because you leave the bike with a pretty small amount of oil. With a small oil volume it doesnt take long for the oil to degrade and be prettymuch useless. We are talking about oil changes every hour with this system (probably an exaggeration) vs oil changes every 10 hours.

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Why is the oil block off kit bad? Lack of lubrication or just because of more frequent oil changes? Just wondering before I buy it.

The wet sump kit is an MX-only mod that was done mainly to lower the center of gravity by moving the oil reservoir to the crankcases instead of having it stored in the frame. While this works to that effect, it's hair-splitting at best, and is a bad idea for recreational and off-road riders for the following reasons:

  • It reduces the volume of oil in the system by about 50%, which will have the effect of reducing the oil's useful life by well over that figure, considering the YZF adds a clutch and transmission into the system. Some people who raced these systems found they needed to change oil between motos. Also, the low capacity means there's no reserve oil in case you develop a leak or an appetite for oil during a desert ride.
  • The sump of the YZF was not designed as a wet sump, so it lacks some of the kinds of internal oil control baffling necessary to prevent oil from sloshing away from the pickup screen, cutting off oil pressure momentarily. With the OEM dry sump system, that's just not a problem because the sump oil is simply pumped back to the tank (frame), the return pump is faster than the feed pump, and temporary interruptions to scavenging oil from the sump don't matter.
  • The dry sump system is, very simply, superior to a wet sump in every imaginable way except for it's complexity.

Do you know why the issue with the seized rods?

Depends on which end seizes. Rolling big end bearing seizures in the YZF's have mostly been related to bearing cage wear and/or breakage. That allows the rollers to skew out of parallel with the crank pin and skid. Small end failures in quads usually proceed by overheating the wrist pin bosses in the piston, which galls the bearing surfaces a forces the pin to rotate in the rod more than normal, followed by that surface deteriorating and forcing the pivoting back to the damaged piston bores.

Of course, sometimes it's just a result of abuse through negligence in maintaining the bike, too.

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on a 400 or 426 would it be advisable to drill a few holes to lubricate the pin boss and bearing?

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I've read in a few places that with this oil blockoff kit it's possible that the oil pump has been removed or disabled. Does anyone know if this is a possibility on my 426?

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I would think you would still have to have an oil pump to get the oil from the bottom end to the top end. I don't see how an engine would survive without it.

Rob

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think hes referring to the oil return pump that would take the oil back to the tank.These engines have 2 oil pumps,the main pump that circulates the oil to vital engine parts and the other returns the oil back to the holding tank for further use.

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That's correct. The kit removes the return pump and routes oil from the sump screen directly to the feed pump. To restore it, you need the complete original return pump and separator plate, both oil lines, and all necessary fittings.

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