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Discussion Starter #1
So I tried to get some riding in yesterday and it just wasnt a good day...

First things first i was out at a local track and the bolt came out of the top of the rear shock... but i caught it in a time so other than a few dings on the top of it, it was still good to go.. (immeditaly thought about the one that caught fire when that happened on here... lol)... So i get that all fixed up and decide to wash it...

After im done washing it i take it for a burn around the yard to dry it off, and it starts ticking very loudly...I shut it off and try and kick it... no way that was going to happen. So I take the valve cover off to see that the actual bolt that holds the decompressor arm to the cam bracket has broke the retaining clip and backed out... Im not sure what broke that circlip but when the arm fell off and busted the decomp all to pieces...

So i change out the decomp to which i found out that you can do it in while the cam is in the engine... saved me the trouble of playing with the timing chain...

Anywho i get that all up and running good agian and head back out to the track (which is about 5 minutes down a back road)... I get there and line up my first jump (thank god it was a table top) and right at the lip of the jump it died... almost went over the bars as the front bumper dug into the top of the jump... good thing i wasnt going any faster... so after it rolls to a stop i tried to kick it over... but there was 0 compression... at first i thought maybe the decomp was stuck open... or maybe a hole in the piston...


After pulling it home i tore it back down and found the decomp to still be good... however the timing chain was off the sprocket.... which i thought was very weird considering i was just in there and it was nice and tight... so i pulled on the timing chain and the whole thing came up... It broke in 2, and it was a heavy duty DID cam chain... it had a extra 2 plates of thickness over the stock one (an upgrade i made after that incident where the timing chain jumped the sprocket)... So i pull all that apart and take the head off... expecting a mess... but to the best of my knowledge the two intake valves hit the piston twice (by couting the rings on the piston) and they bent and stuck open... Everything else looks good..


So I have a question... how does one go about removing the bent valves? I was thinking just cutting the tops off them and sliding them out through the bottom... that way i wont have to push them up into the head to remove the retainers and whatnot...

Also has anyone else ever heard of snaping a timing chain? I didnt think there was that much stress on the valve train... but maybe i was wrong...

Are there any advantages over running something other than stock valves? If not ill just go with stock as they have seemed to hold up pretty well in my machine...


I will add some pictures when i get home from work today... although there isnt much to see... other than the way the chain broke... which looks like there was alot of force on it when it did break.... It just blew apart....
 

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Is it possible that when the decompressor went south that a piece of something was in there to later get into the chain and break it?
 

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Im a firm believer in replacing the timing chain yearly because they start binding up. I have went through 3 in 3 years, they are considered a wear item in my eyes.

KW, Ferea or stock valves dont really matter in the 04/05 motors they are all good with stock CDI. I think the stock may be a tad bit lighter if youre concerned with that.

I run stock springs with KW valves because I got a good deal on them, whatever you think is good will be fine im sure.
 

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Discussion Starter #4
This timing chaing was not stretched nor did it bind on any link... mind you it broke mid link...

As for the decomp dropping a piece in the engine... I found both sides of the clip that broke and every piece was accounted for before i put it back together... I made sure of this....


So did the intake valves hit the piston causing the chain to break? or do you think the chain broke and caused the valves to hit the piston?

Im just glad i didnt lose my top end from this...
 

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This timing chaing was not stretched nor did it bind on any link... mind you it broke mid link...

As for the decomp dropping a piece in the engine... I found both sides of the clip that broke and every piece was accounted for before i put it back together... I made sure of this....


So did the intake valves hit the piston causing the chain to break? or do you think the chain broke and caused the valves to hit the piston?

Im just glad i didnt lose my top end from this...[/b]
I would bet that the chain broke first leaving the intake valves open, thus hitting the piston.
 

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Discussion Starter #6
Yea thats what i was leaning towards as well..... but it sure looked like it would have taken alot of stress to break that chain...
 

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To start with the only way the timing chain would break because the intake valves were open the cam would have to be in that postion and the valves stick. Which is probably what happen.

You said you had wash your quad I bet if you look at the guides there will be rust there which caused your problem (stuck valves).
 

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If the timing chain broke first, how would the valves get hit? As soon as the chain snaps, the cam is free to rotate on its own. If the valves were open the spring pressure would surely try and close the valves, thus rotating the cam (any direction at this point) and closing all the valves. At least that's how I see it happening in my head. The only way it could snap the chain first is if it snapped, it somehow bound up on the cam sprocket, but there's just too much room up in the valve cover and I dont see that happening.

Do you think it's possible you floated the valves, they bent and got stuck in the head and the chain snapped? I cant believe the chain even snapped, I didn't think the stock 450 chains were that much of an issue, and I've never heard of anyone even upgrading to a heavier chain, I cant imagine that one breaking!?
 
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