07 YZ450F Cam chain

i counted 14 links between the indexing marks. when i rotated the motor counter-clockwise,
What exhaust cam does it have? 14 pins is only correct if it is a 400/426 using the OEM 450 cam, and it that case, the timing mark on the exhaust will appear 1 tooth too far advanced.

A YZ400/426/450 should show 13 pins between cams, not 14.

i will take a picture of the cams at indexed TDC and post it. maybe you can tell me if i am counting wrong, or if i am completely off in left field. i am holding on to a glimmer of hope that this cam tensioner is the issue. i have been scouring the forum and everything points to it. you and Goose 07 have been extremely helpful. thanks for the input. like i said i will take a picture after the youngi'n goes to bed and i can sneak out to my shop. i don't get a lot of time out there with a 2 year old and another on the way. Mamma needs all my help and money so i sure hope it's just jumped time.

i got some pictures Grayracer and upon further inspection i believe that it jumped a tooth. my camera data cord is at work so i will upload the pics tomorrow in the A.M. with a single tooth jump what type of valve damage do you think could have happened. should i just go ahead and pull the top-end and replace the valves and have the seats 3 angled? i don't want to have to open her up again till it's rebuild time due to hours not trouble. please advise. thanks

A single tooth may not have caused any damage. I'd try re-timing it and see how it is after that.

so to re-time should i take the cam retainers off and basically re install the cam chain from scratch? do you think i should replace the tensioner also? i really appreciate your help. if you are ever down here in Texas look me up and i will take you out for a plate of BBQ and a beer.

If in fact it is out of time, and only one of the cams appears out of place, align the engine at TDC and remove only that one to reposition it. Be very critical of the process of reassembling and retorquing the cam in its saddle.

While the cam is out of place, check the chain for any tight, "kinked" links, those that do not move freely. It may be worthwhile to remove both cams in order to thoroughly inspect the chain. Also look for signs of scoring or galling in the cam caps and saddles. The tensioner is not expensive, and for that matter, neither is the chain. Once you have had this problem, the wisest choice is likely to be to just go ahead and buy both parts new in case they suffered any damage when the bike skipped time.

I'd say go ahead and pull the whole top end off to see what your piston and valves look like...

I believe I had a domino effect starting with the cam tensioner failing (maybe Gray can put together the CSI chain of events) that resulted in my rings failing (shortly after I replaced the cam chain and tensioner thinking all was good) allowing enough movement of the piston to cause the piston to slap the head (and a couple valves)...:banana:

I ended up buying a complete new motor for $2000, then parted out the stuff I didn't need, along with some other stock stuff I'd been holding onto, and made my money back plus a little...:busted:

So yeah, changing just the tensioner and chain got me up and running again, but slight problems that probably stemmed from it going out of time, quickly turned into big trouble when I was blowing so much burned oil out the back, nobody wanted to ride behind me!:banana:

All has been good since though, and I think I've finally got this beast dialed in perfectly and can trust it to go hours from camp ...:busted:

(I need a bigger tank! I'm tired of having to bring a couple water bottles of gas in my hydropack)

Good luck man, keep us posted what's going on (pics too)...

can't seem to get the pics to load???????

yzmotorshots005.jpg

this is the cam assembly at TOP DEAD CENTER.

yzmotorshots002.jpg

these are the fly wheel indexing marks at TDC. sorry thats the best picture that i could get.

any input?? Am i totally off in left field? or does it look like it jumped time? thanks.

To start with, the engine does not appear to be at TDC. As bad as the picture is, it looks as if the "H" timing mark is aligned with the index on the case. The engine should be rotated forward until the "I" is aligned instead. That will probably correct the perception that it's out of time.

Otherwise, I see both cams timed correctly in relationship to each other (13 pins), but slightly retarded, which I would expect if the wrong timing mark were used.

Here's a pic of mine for relation...You can see the marks on the cam sprockets to the far right and far left lining up with the top of the case...

DSC04299small.jpg

Otherwise, I see both cams timed correctly in relationship to each other (13 pins), but slightly retarded, which I would expect if the wrong timing mark were used.

That's what it looks like to me also.

A buddy of mine had his '08 with 55 hrs on the meter jump time this weekend.

He said it started making a hell of a racket for a few seconds then died. He could just barely get it kicked over, pushed it back to where we were staged and kicked it over so I could hear it and it had a bad clanging noise like there was some piston/valve contact...?

We pulled the valve cover and it looked like the chain jumped two teeth...the cams were still indexed to each other correctly so I'm guessing it jumped at the crank sprocket. The journals in the cam caps had some slight scoring.

I pulled the cams and reset the cam timing at which point to bike fired up and ran fine without any unusual noises. Go figure...I would have thought that it wasn't going to run after listening to the racket it was making when he kicked it over.

there are three marks on the fly wheel. none looked like an "H" all three looked like an "I". so i am going to assume that the first 2 marks are the "H" and the third mark is the "I" . so looks like i need to start again.:busted::banana: sooner or later i will figure it out

That's what it looks like to me also.

A buddy of mine had his '08 with 55 hrs on the meter jump time this weekend.

He said it started making a hell of a racket for a few seconds then died. He could just barely get it kicked over, pushed it back to where we were staged and kicked it over so I could hear it and it had a bad clanging noise like there was some piston/valve contact...?

We pulled the valve cover and it looked like the chain jumped two teeth...the cams were still indexed to each other correctly so I'm guessing it jumped at the crank sprocket. The journals in the cam caps had some slight scoring.

I pulled the cams and reset the cam timing at which point to bike fired up and ran fine without any unusual noises. Go figure...I would have thought that it wasn't going to run after listening to the racket it was making when he kicked it over.

Ya, it even ran great for two and a half laps of a hare scramble the next day before it dropped a valve. Oh well. Such is life I guess.:busted:

Ya, it even ran great for two and a half laps of a hare scramble the next day before it dropped a valve. Oh well. Such is life I guess.:busted:

Aww damn...so you ended up racing it yesterday, huh? Did you replace the timing chain before you raced?

there are three marks on the fly wheel. none looked like an "H" all three looked like an "I". so i am going to assume that the first 2 marks are the "H" and the third mark is the "I" . so looks like i need to start again.:busted::banana: sooner or later i will figure it out
If you look a little more closely, you should be able to see a crossbar between the first two marks, making it appear to be an "H". But you are correct, it is the third mark, counting left to right that is the TDC mark.

thanks, i will take new pics tonight. i gotta get back to riding!!!! I am going through withdraws!! all the corn fields are freshly harrowed and it has rained a bunch this last week and i am drooling over the soft moist dirt. fresh drainage terraces to jump and no bike to do it on!!! waaaaaah!!!

same thing happened to me. I rebuilt my 07 yz250f and put an OEM yamaha timing chain in it and 30 hours later it skipped time causing the pistion to actually bend and break off the head of one of my exhaust valves. And blew a hole through my piston

last year my brothers 07 yzf 450 dropped an intake valve which broke off destroying his head which had alot of work done to it cracked the jug and bent the con rod. when i rebuilt the motor i did every bearing, seal, did a stroker crank (balanced) big bore kit new head oem new cam chain and kibble white stainless valves. so the bike has 12hours on the meter since the rebuild and the cam skipped twice now in 3 short rides. I have the thing apart in my garage waitting for a new oem chain and tensioner. the intake was out (retarded) 45 degs.

here are some pics

http://i745.photobucket.com/albums/xx97/ringet421/HPIM1903.jpg

http://i745.photobucket.com/albums/xx97/ringet421/HPIM1898.jpg

What you need is a new cam, maybe some head work. From the pictures, the exhaust cam is timed correctly, and the intake is a tooth advanced. However, from the second picture, assuming both were taken in the same crank position, the cam is nowhere near where it should be given the position of the sprocket. This makes it appear to me as though the cam sprocket spun on the shaft, which is quite often caused by a seizure at the cam/head, which typically results from oiling problems or assembly faults.

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