08 YZ450F Timing Marks Don't Line Up


11 replies to this topic
  • MotoMike_205

Posted May 07, 2012 - 05:43 AM

#1

Guys,
I bought the bike new and have about 65 hours on it
I haven't done anything to the motor and tried checking the valves for the first time yesterday
The manual says to line up the fly wheel mark with the side case and line up the cam marks level with the top of the head.
Exhaust cam mark at 9 oclock and intake cam mark at 3 oclock
When I line up what I think is the fly wheel TDC mark, the cam marks don't line up level with the top of the head.
As I rotate the fly wheel a little more counterclockwise, there are two other marks on the fly wheel that make a rectanglar shape.
What are these marks on the fly wheel for?
If I line up the cam marks level with the head and check the valves they're not that bad
Exhaust valves .007 intakes approx .004
Could this mean the cam chain jumped a tooth on the crank?
Not sure how to proceed?
Thanks for any help.
Mike

  • grayracer513

Posted May 07, 2012 - 07:04 AM

#2

There are 3 marks on the flywheel within about 10 degrees or less of each other. The first two, reading from right to left, are normally joined by a horizontal line to form an"H". These are for strobe checking ignition timing at idle. The third mark (farthest clockwise) is TDC. If you're confused, check TDC by using a Phillips screwdriver down the plug hole.

The only timing mark to be considered when aligning the cams is the one at 9:00 on the exhaust, and the one at 3:00 on the intake. Ignore all of the others while inspecting the timing. It is not unusual for the marks to fail to line up perfectly because of chain wear, etc. If you suspect the timing is off, imagine the mark on the cam being at the next tooth over which ever way you think it should be and see if that would make it look better aligned or worse.

If the timing is off, and it got that way on its own, get a new chain. Carefully inspect the tensioner for smooth operation, and replace it if you are at all suspicious. Tight, binding pivots in the chain is the most common culprit. Also check the cam saddles for signs of seizing or galling.

  • MotoMike_205

Posted May 07, 2012 - 07:51 AM

#3

Thanks for the info grayracer and clarifying the other two marks are the H mark for strobe check.
From your description, the third mark TDC is what I set the crank to and saw that the cams where off.
The timing must have gotten that way on it's own because this is the first time I've checked anything.
As far as smooth operation, when turning the crank, I can feel a stiff spot and then feel it release as I keep turning.
Could that be the tight, binding pivots in the chain as you mentioned?
On the Yamahas, is it common for timing chains to go bad before valves need adjustment?
I haven't inspected the tensioner or cam saddles yet and not sure if I should just order a chain or keep checking things.

  • grayracer513

Posted May 07, 2012 - 08:54 AM

#4

It's not unusual for the piston to need replacement before the valves need adjusting, really. You should check TDC with a probe to verify you're looking at the right mark. "Smooth operation" as I used it referred to the operation of the tensioner itself. The tight spot you feel could be a valve in contact with the piston.

Timing chain failure in YZF's is usually a matter of the chain becoming stiff at the pivots, which is, IMO, related to the choice of oil and the oil change intervals. This condition cannot be inspected for with any degree of thoroughness on a practical level without removing the chain. The chains are cheap at less than $20, and should be replaced annually, just as a preventive measure.

  • Yamaryder29

Posted May 07, 2012 - 09:00 AM

#5

Your timing chain is stretched.I usually change my timing chain every 40-50 hrs. It is not uncommon to for the chain to stretch before needed a valve adjustment. I have an 08 and i'm on my 3rd timing chain without needed a valve adjustment. For $19, replace your chain or let it stretch and jump time and take your top end.Top dead center ius the"I" mark on the flywheel.

Edited by Yamaryder29, May 07, 2012 - 09:01 AM.


  • MotoMike_205

Posted May 07, 2012 - 01:00 PM

#6

So if the tensioner and guides are ok, are there any other parts that get changed with the chain?
Does the crank gear that the chain is driven by get replaced and do I need any special tools?

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  • Yamaryder29

Posted May 07, 2012 - 03:09 PM

#7

So if the tensioner and guides are ok, are there any other parts that get changed with the chain?
Does the crank gear that the chain is driven by get replaced and do I need any special tools?

You can inspect those parts for wear. 99% of the time they are fine. To change the chain you need a flywheel puller, they make them specific for a yz450f. It'll cost $15. After the 1st time it's paid for.

Edited by Yamaryder29, May 07, 2012 - 03:10 PM.


  • grayracer513

Posted May 07, 2012 - 03:54 PM

#8

The flywheel puller is the same one as used on '02-'08 CRF450's. The crank gear is cut directly on the crank. Normally doesn't need much attention.

  • MotoMike_205

Posted May 09, 2012 - 05:38 AM

#9

Thanks for the info guys!
You're both saying chains are less than $20
Where do you find the chains that cheap?
I looked on RockyMountainATV and Motosport and they're both selling them for $70

  • Yamaryder29

Posted May 09, 2012 - 06:10 AM

#10

Thanks for the info guys!
You're both saying chains are less than $20
Where do you find the chains that cheap?
I looked on RockyMountainATV and Motosport and they're both selling them for $70


You were checking out the wrong chain.
http://www.rockymoun...oem-schematic/2
Go to this link, then select camshaft chain.

  • grayracer513

Posted May 09, 2012 - 06:57 AM

#11

TT OEM parts sells them for $17.something, and Yamaha's retail price is like $19.50 or thereabouts.

  • MotoMike_205

Posted May 30, 2012 - 07:45 AM

#12

Thought you guys might want to know how things went when I Installed a new timing chain and spark plug in my 08 YZ450F.
The engine marks I thought weren't lining up was incorrect.
When I pulled the side cover off, I stuck a plastic straw down the spark plug hole to check for TDC.
I turned the crank until the straw topped out so I knew it was at TDC, then looked at the fly wheel marks.
The TDC mark is to the right of the H mark.
Aparently I was looking at a mark on the fly wheel that turned out not to be a mark, the darkish colored mark I was looking at through the access hole when I checked the first time before taking the side cover off turned out to be a spec of debris because I was able to wipe it off the fly wheel.
The mark that turned out to be debris was to the left of the H mark so no wonder the timing looked way off when I checked the first time.
When I got the old timing chain out and put it next to the new one I could see it stretched out longer than the new one.
After I got everything back together and put fresh gas in, it fired up and ran ok.
I took it to a small local track to ride on dirt and it ran pretty good.
At least I got a new chain installed and I'll know what I'm doing the next time plus If I want to install a new piston and ring I'll pretty much know what to do when it comes to installing the timing chain and cams.
Thanks again for all your help!

Mike





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