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05 Yz 450F won't start

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OK, so I put a athena big bore kit in my 05 yz 450f and everything went back together nicely and I got it to fire up.... after I took it for a ride I wanted to change the oil just incase their was any dirt or anything inside just incase. And after I changed the oil I can kick it and kick it and kick it and now it wont even fire I even tried pull starting it but nothing. I checked if timing marks they were all lined up. the valves where all in specification according to the manual. I even replaced the timing chain I thought it was that? it has spark and compression and when I pull the spark plug out it is wet! I Have even cleaned the carb with carb cleaner and it was jetted properly before it was shut off so any help here guys I am really lost and don't know where to start anymore.... I want to sell it because it doesn't seem worth it anymore. :banghead:  

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Has to be something simple, if it ran after the rebuild

You probably just flodded it.

 

Turn the throttle wide open, hold the kill button on, and kick it dozens of times to clear the cylinder

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I have just tried what you said to try and still no luck even pulling behind the quad never started it...

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Ok I had my stator replaced and the cdi box now I have spark but now wont start still but is starting to make a backfiring sound

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Tomorrow when I get time I will pull the valve head assembly off and check to see if there are any bent valves or anything out of the usual

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Try a brand new plug, I have had plugs that spark outside the motor, but change the plug ans its all good again. Did your bike feel richnwith the new big bore?

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It's not a matter of 'replacing them'

 

You either jumped multiple teeth, or broke your cam chain tensioner (which then jumped multiple teeth...)

 

You ran the motor for too long without doing the required maintenance on the head,  and now you have to rebuild the entire head, replace the cam chain, and cam chain tensioner.

Edited by TheKoolAidMadeMeSick

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The top of the piston is unharmed somehow thankfully and I have another cam chain coming in the mail along with the tensioner

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The top of the piston is unharmed somehow thankfully and I have another cam chain coming in the mail along with the tensioner

 

...yes, but you will need to get your head recut at the seats for the new valves, replace the valve guides and seals, and probably it's time for a piston and rings too.

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Then no, your piston and rings are fine. Verify the valves are leaking. While they are fully closed, spray carb cleaner above them and see if it leaks through. If so.. push the valves down and visually inspect the bevel that presses against the seat. It will either be black and nasty or they will now be sharp as he'll on the edge, which means they are worn and ruined. If they are black and nasty but not sharp, this can be fixed by removing them, vigorously cleaning those and the valve seat witb a copper brush and 're swimming you're valve clearance at tdc. I once had a valve shim smash another spacer in the head in a matter of a ten minute ride, which caused the same problem. Inspect all other parts that may contact the valve for concave imperfections.

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Ok so after getting my valve head redone: recut, new valve seals and guide, new timing chain, new tensioner. I went to install it and installation went good.

now after I went to start it. Now the kickstart wont even budge help me please?? im lost here. before and I was able to kick it over this was before I got the valve head back from the shop.

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Were you able to rotate the cams after you torqued the cam caps down? are the cam retainer clips in place correctly? Did you rotate the engine a couple of times by hand and then recheck the timing? Did the crank rotate before you out the head on? Are you sure the timing chain is correctly in the crank sprocket? Where things moving before you out the tensioner in, did you back out the tesioner to the detent before you torqued it up and then released with a flat blade screw drver under is own spring tension? You should do a whole lot of checking each step before you start swinging on thr kick starter!

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So after investigate ing I found that the head was built inproperly he had forgot bore out one of the valve guides I dont know how and because of this the valve wont open up and the company is willing to replace the whole head for free.

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