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Thesolidman1

2006 YZ450 got hot and siezed, stock w/ 40hrs

19 posts in this topic

Hi, riding my 2006 YZ450 Thursday, my bike siezed up. My friend who was riding behind me said he smelled something. This bike has 40hrs, is stock, (except for jetting). I changed the oil every 3-4 hrs. I drained the engine oil and measured it and it was exactly 1 qt. I also drained drained the coolant and it was just a tad short of 1 qt, which is the capacity of the system. The track was hardpacked and it was a cool day. Probably the about the smallest load on the engine of any riding conditiions. I have not tore the bike down yet, but I cannot understand what would cause such a dramatic failure with all fluids good, and easy conditions. Maybe the waterpump failed? Seems unlikely. I have not tore down the engine yet. This will be my first 4 stroke rebuild. It is my hope that only the top end is damaged. Anyway, I don't know the cause, and was hoping someone out there could help. Thanks friends!!

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Carefully check the coolant and oil pumps. You will need to know what seized in order to find out why.

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Thanks Gray, when I get time to tear it down I will repost with additional. Also, thank you for your son's service to our country!

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Also, check oil pickups.

It is not extremely common, but it does happen in all makes and models of bikes. The factory sealant (if they accidently use too much) can be a culprit, as well as milling materials (which are almost always present in the cases, but sometimes moreso than others) can accumulate on the pickup, and restrict oil flow.

This is the reason I drain the oil in ANY new bike I purchase first thing, run it, and drain it again. I use cheap oil for that, then put my normal oil in.

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Yes and no. Distance the oil travels from the oil tank to the feed pump is quite short, but you can't get to the oil tank end of the passage without splitting the cases. There is no screen on it in any case.

The return screen is also located between the cases, but it is "semi" accessible through a port below and behind the magneto flywheel.

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my cam chain went to $hit in my 06. it got so stiff so fast when my bike died i could not turn it over. it was "seized". with all of my weight on the kick it wouldnt turn over. tore it down thinking my auto de-compression thing was messed up but it was the cam chain...i think it was due to sand in my oil tho:(....haha it was kinda funny...when i finaly got my cam chain out it would hold its shape no matter what position you held it in.

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So it sounds like I should carefully inspect the oil pump, not worry too much about the pickup since it's inside the cases and has no screen on it, and also check the "return screen" for blockage? And that would be on the other side of the engine from the oil pump? Thanks

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That's interesting. Maybe the cam chain has something to do with it. It was siezed at the track, when I got it home it will kick over but makes a terrible grinding sound, it's ugly. Did you replace the cam chain sprockets with the chain or just the chain? Thanks guys..

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i only replaced the chain. the sprockets were not worn very bad. if your bike is making grinding sounds you got some problems:( it will probably be more expensive than a cam chain. how is it to turn over? like stock, loose or harder? dispite the grinding

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That is not all the uncommon with Two strokes... but I haven seen that with 4 strokes much.

With a two stroke, it is usually a "cold seize" where the piston heats up and expands and locks up. Also a 4 corner seize. But when it cools it can roll over again but the damage is done.

Could be similar with a 4 stroke though, but I would bet it is in the crank, not a piston to cylinder seize.

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seems some of the 06 cam chains did have some stretching issues creating failures from jumping teeth.......these need to be checked and/or replaced

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The trouble with the '06 chains that have failed is not so much that they have stretched, they kink and bind up.

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I wonder why they would use a different chain manufacture? Is the 06 chain different from ALL the 450s?

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I pulled the engine mostly apart last night. The top end is fine. I pulled the right side crankcase cover off. The oil pump drive gear was in pieces, the oil pump case was cracked, and pieces of the gear wedged behind the clutch and the rivets that hold the primary gear to the clutch basket were machined right off. Pretty weird. Worst of all, the crankcase is broken where the oil pump drive shaft gear goes in. I priced the crankcase, you have to buy the pair, and the cost is almost $700. This sucks. This bike has 40hrs and has been babied. Clutch basket is over $300, but I think I can get a hinson and swap over to it. I don't know what caused it, but I'm guessing the either the oil pump siezed up, or the drive gear just broke on it's own. If anyone has any suggestion how I can get a crankcase for a reasonable cost i'm all ears.

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