2006 yz450 Seized Engine: Dropped valve or timing chain stretch...

So today while riding we came to the top of a hill with a two foot ledge and no good approach angle so I got close to the edge and went to pop my tire up onto the top of the ledge and I gave it some gas and let out the clutch. It didn't hook up like I needed so I tried again and as I went to give it gas and let the clutch out, the engine maded a clacking type noise and died. I didn't wrap it out it only briefly raised the rpms before it died. I tried cranking it over and it went a rotation then stopped.....

When I got home I was thinking snapped cam chain balled up in the bottom end. I pulled both side covers, but first the ignition side, the chain was tight and no filings in my oil that onnly had 30 mins on it. I pulled the whole right side cover thinking that it might be something on that side and the same thing thte oil that I saw was clean and not bad at all, and I could spinig the engine backwards until it got to the bottom of its stroke.

So I'm thinking that I dropped a valve and its stopping the piston at TDC and then maybe one of my cams is hitting something that is messed up in the head and stopping it at BDC. I won't have time to tear the head off till next week but I was hoping to pick some of your brains with thoughts or suggestions before I get to the point. i can't think of any way to cam chain could ball up and not look ok. As well I can.t think of anything else that would make the piston stop in its stroke at TDC and BDC or just short of each, its kinda hard to tell when you can't make a full rotation.

Either way I'm thinking that I'll be replacing a cam chain its due for sure. I've already got 30 hrs on it this year. I'll probably install my big bore kit and the WR 1st and 5th if I'm going to have it apart. I just hope if it is valves that I don't have a messed up head like some of the similar situations that I was reading about on here.

Thanks guys!!!

So today while riding we came to the top of a hill with a two foot ledge and no good approach angle so I got close to the edge and went to pop my tire up onto the top of the ledge and I gave it some gas and let out the clutch. It didn't hook up like I needed so I tried again and as I went to give it gas and let the clutch out, the engine maded a clacking type noise and died. I didn't wrap it out it only briefly raised the rpms before it died. I tried cranking it over and it went a rotation then stopped.....

When I got home I was thinking snapped cam chain balled up in the bottom end. I pulled both side covers, but first the ignition side, the chain was tight and no filings in my oil that onnly had 30 mins on it. I pulled the whole right side cover thinking that it might be something on that side and the same thing thte oil that I saw was clean and not bad at all, and I could spinig the engine backwards until it got to the bottom of its stroke.

So I'm thinking that I dropped a valve and its stopping the piston at TDC and then maybe one of my cams is hitting something that is messed up in the head and stopping it at BDC. I won't have time to tear the head off till next week but I was hoping to pick some of your brains with thoughts or suggestions before I get to the point. i can't think of any way to cam chain could ball up and not look ok. As well I can.t think of anything else that would make the piston stop in its stroke at TDC and BDC or just short of each, its kinda hard to tell when you can't make a full rotation.

Either way I'm thinking that I'll be replacing a cam chain its due for sure. I've already got 30 hrs on it this year. I'll probably install my big bore kit and the WR 1st and 5th if I'm going to have it apart. I just hope if it is valves that I don't have a messed up head like some of the similar situations that I was reading about on here.

Thanks guys!!!

30 hrs on the chain and you want to replace it?, my 450 ive got probably over 100 hrs past 2 years of riding, and im debating whether to touch it this year, and if i do, its to put a high comp piston in,

but in theory, it does sound like could be a dropped valve, if it broke off while running chances are you head will have a real nice dent into it :thumbsup:, also why it stops at the bottom could be, because if that valve dropped or broke off from the stem, either way i look at this i would forsee your valve springs rising up and coming out of place up on your head so it could be jamming up your cam in there, so stopping at the bottom, but its all theories until you get that sucker opened, all you gotta do is pull your gas tank off and pop off the top cap to the cams and you should see whats going on possibly, wouldnt take too long?

Major engine failures in YZF's, when they happen, fall mostly into 2 categories: failed cranks and valve gear failures. Valve gear problems are easily half or more of all of them, and far more than half of the valve gear failures are either caused by the timing chain, or subject the chain to damage.

The chain costs $20 or less.

Replace it annually, anytime there has been any other major failure, or whenever you're that deep in the engine to start with.

"Major engine failures in YZF's, when they happen, fall mostly into 2 categories: failed cranks and valve gear failures. Valve gear problems are easily half or more of all of them, and far more than half of the valve gear failures are either caused by the timing chain, or subject the chain to damage." I haven't followed your advice concerning cam chain replacement, but I was going to replace it soon :thumbsup:.  

Weird note I rode the bike 2 weekends ago and the oil level was fine, then my buddy bought a new bike this week so we went monday night and then i decided to change the oil before we went today. My oil was waaay low i didn't get anywhere close to a quart out of the bike. no puddles under the bike and being as the valves haven't been serviced for a very long time i'm guessing that the valve guide are worn out, and it was burning through it? Though I didn't smell or see burning oil. I'll probably pull the valve cover then the head off today and see what it looks like. btw gray do you get $20 chains from thumper talk? The ones with rocky mountain atv mc are like $80

Edited by sledtrash

do you get $20 chains from thumper talk? The ones with rocky mountain atv mc are like $80

$20 is retail for an OEM Yamaha chain. Made by Borg-Warner Japan, same as the Pro-X chains. TT lists them for $17.55

So the right outside intake valve is sheared and stuck sideways in its chase and the right exhausts valve is bent and the other exhaust valve seems like it has problems as well. The head is pretty gouged up so it looks like a new head, the piston has some major gouges in it as well so i'll probably be putting my big bore kit on it probably just do a complete rebuild.... I don't know when it will happen its going to be an expensive build.

Contact Engine Dynamics about fixing the head. They can turn some pretty disastrous looking junk into usable heads for way less than a new one.

Do yourself a favor, replace the crank now. Even if it seems fine right now, you will more than likely have a crank problem within a few hours of running it. I had a bike jump time and bend the exhaust valves with 45 minutes on the motor. The crank seemed fine, so I didn't replace it. 5 hours later the crank failed and damaged my cylinder and piston in the process.

Well I plan on splitting it and making sure that the crank is balanced but it was new last winter as I put a WR crank in for my lighting. But I will post some pictuures later today when I have access to a real computer.

Like always gray thank you for the helpful info!!!

Edited by sledtrash

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yup there it is....

So Gray, I was wondering if the heads from the older engine would work or if it is just the 06-09 heads??? I looking at parts on ebay and I'm wondering what to consider?

i'd say your best to buy a whole new head with valves and all that for about 500$, the damage to that head could be fix'd probably but the cost is probably going to be around the same anyhow between the machining and welding to or what ever to fill in all that dents and stuff, and valve seats... etc, just my opinion on that though!

So Gray, I was wondering if the heads from the older engine would work or if it is just the 06-09 heads??? I looking at parts on ebay and I'm wondering what to consider?

Only the '06 -'09 heads fit. You could use a head from an '07- '11 WR450, but you'd have to plug a couple of holes and the performance might also suffer slightly.

You haven't called Engine Dynamics yet, have you?

i'd say your best to buy a whole new head with valves and all that for about 500$, the damage to that head could be fix'd probably but the cost is probably going to be around the same anyhow between the machining and welding to or what ever to fill in all that dents and stuff, and valve seats... etc, just my opinion on that though!

Obviously not based on any facts whatever. EDCo can probably repair that head for less than the cost of a decent used one on eBay. A new bare head runs $580 with a discount, the valves are $70 each, and the lifters are $25. That's $955, and we're not done yet. The difference between reality and the number that you "came up with" will likely repair the head he has.

Thanks Gray! I haven't been arond the older styled 450 so I wasn't sure if they were the same and could be used. I'm planning on calling them sometime this week, I have college finals this week so I'm trying to make myself study as much as possible. I appreciate the responses.

Obviously not based on any facts whatever. EDCo can probably repair that head for less than the cost of a decent used one on eBay. A new bare head runs $580 with a discount, the valves are $70 each, and the lifters are $25. That's $955, and we're not done yet. The difference between reality and the number that you "came up with" will likely repair the head he has.

not sure, looking now, a head is yeah like 900 on ebay,i co uld of sworn back when i had engine troubles that a head was about 550 or so with valves, but could be wrong, and probably am as i am seeing

You can get used ones for that, but then there's always the question of how used it is.

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