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max49

Catastophic Failure

28 posts in this topic

My son's '07 YZ450 seized 3/4 of the way through a mostly high speed MX style enduro 75 mile today.

The bike has never used any oil before but I checked the oil before the race and it seemed a 1/4" low, so I started it and let it idle and shut it off for a couple minutes and checked it and the oil was a little high.

The bike seized during a long straight where he was riding 5th gear pinned. When it seized, the rear wheel did not lock up, and he was able to coast to a stop. After we got the bike off the course, the dipstick was dry. There were no signs of any oil leaking or blowing out. When we drained the oil we only got a few oz. of black and what seemed like very thin oil.

Can you guys think of any explanation where the oil could have gone? It might not do much good but it would be good to know if a failure could cause the oil to go somewhere or if lack of oil caused the failure.

The exhaust was pretty much dry and the antifreeze was an oz. or 2 low didn't seem to have oil in it.

We put a new clutch in a couple of weeks ago and the new clutch seemed to be working perfect. It had about 75 to 100 miles on it.

At this point, it is impossible to push the kickstarter down. We also noticed that when keeping the bike in gear, and pulling in the clutch, the bike moves with zero resistance. In the past, it has always been difficult to push the bike in gear with the clutch in compared to pushing it in neutral--now they feel the same. Could this have something to do with the failure? But even it did, I still don't know where the oil could have gone.

With a seizure like this, what are the odds that this damage could be limited to the top end only?

Thanks in advance for your ideas.

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If it didn't leak it, or pump it into the cooling system, it had to have burned it.

The lack of clutch drag is due to the absence of oil between the plates.

In the absence of oil, the piston should be the first thing to fail, followed closely by the cams, then the big end. Time for some exploratory surgery.

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I just seized my 06 YZ450 from no oil, just needed a piston, rings and cylinder.

I know why I had no oil though.....

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I just seized my 06 YZ450 from no oil, just needed a piston, rings and cylinder.

I know why I had no oil though.....[/QUOTE]

Let's hear it.:worthy:

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oil bolt fell out....I needed a new top end anyway:smirk:

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you will need to dissassemble it to really be able to access the situation. Drain the antifreeze and look for any oil mixed

Curious how long was 5th gear pinned and for how far?

Grey curious if it burned it the exhaust would be bellowing smoke right?

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Grey curious if it burned it the exhaust would be bellowing smoke right?

Not necessarily. To burn through one liter of oil in 55 miles at an assumed average of 7000 rpm in 3rd gear, the engine would need to burn .014 cc each time it fired.

How much smoke would that create, and how important is oil control?

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Curious how long was 5th gear pinned and for how far?

I'm Max49's son and was the one riding it when it seized. The enduro had 2 long straights in the section of the course where it seized, and each were between a 1/4 mile and a 1/2 mile. I would estimate that I had 5th gear pinned for about 5-7 seconds on each straight.

A minute or two prior to the engine seizing, coming out of a corner, it seemed to "skip a beat" when getting on the throttle--similar to when you're about to run out of gas. It only did this once, though, and I knew I had plenty of gas, so I didn't think too much of it, until it sputtered to a stop a few minutes later.

Thanks for all of the ideas so far. We're planning on taking it to a trusted mechanic soon, but being a college student with bills to pay and tuition due next month, I'm trying to research what could have caused the engine to seize so I can get a better idea of how much money it's going to take to repair it.

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I'm trying to research what could have caused the engine to seize so I can get a better idea of how much money it's going to take to repair it.
There's no relationship between the cause and the cost. The actual damage is going to determine that.

The cause is always interesting, and can, at least in theory, help prevent a repeat failure, but the evidence is often destroyed by the failure in such cases.

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I don't know GR, I keep hearing these stories pop up that sound a hell of a lot like what I went through with the cam tensioner failing...:worthy:

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Thanks for all the replies.

Grayracer, lack of oil sounds like an informed explanation as to why the clutch had no drag when pushing in gear. Thanks

I took the cover off the clutch any way and every thing in there looks fine.

I also drained the anti freeze and it looked like new.

Thanks for the encouraging words WGP, I'd feel lucky if all we need is a cylinder, head & rings.

I talked to the owner of the shop I will probably take it to. He said he thinks there must be a hole that I have'n't found.

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When I blow compressed air into the oil fill hole, the air comes out the big black hose in the top of the head and discharges on the bottom left side of the engine. Is this normal?

It was not obvious , but is it possible that the oil could have been pumped out this hose? If this is possible, it could have come out and went straight to the ground without getting all over the bike.

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1) When I blow compressed air into the oil fill hole, the air comes out the big black hose in the top of the head and discharges on the bottom left side of the engine. Is this normal?

2) is it possible that the oil could have been pumped out this hose? If this is possible, it could have come out and went straight to the ground without getting all over the bike.

1) Yes. That's the crankcase vent, and that's why it's there.

2) No. If 200 cc had come out the breather underway, the mess down the side of the bike would be phenomenal

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That darned plastic allen head plug on the left engine case cover (06 YZ450F and all YZ250/450f's for that matter) has a nasty habit of coming out. I lost mine on a couple of practice laps before a race and thankfully noticed the oil all over my left boot. A guy who wadded it up earlier gave me the one out of his bike before leaving for x-rays and the day was salvaged.

Needless to say, I now always check that plug before a ride. I also now keep a spare of that sucker as well.

Your issue seems weird Max. Good luck and let us know where the leak was if you will. Thanks also to GR for the continual great info and advice.

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When was the last time you replaced the piston you probably burned a hole in it or broke the piston and oil burned up in the exuast. I have broke two pistons in my yzf400 both in the 3rd season of the piston.

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