2008 YZ450 Valve adjustment help

I always find at least one out of speck.

All my bike were.

I am kind of picky, i even took a couple of 185's and used 600 grit wet and dry paper on a piece of glass to make a 183 and a 184.

i like perfection.

Heat has a little to do with it too Desert gets hotter than the Colorado Mountains.

I would make adjustment at room Temp

Grey-Yes it has compression and will turn over with the ratchet with ease.

Grey-Yes it has compression and will turn over with the ratchet with ease.
Which is it? If it turns over, but comes up against a "hard spot" as the piston starts upward, forcing you to push harder to get past it, it has compression. If you say it turns over easily, it sounds like it doesn't.

Grey- I meant to say that it turned over easily with no binding. Anyways I pulled the head off this morning and found a broken intake valve that was sank into the head. m_856a9da7c58f43c5a6339b1802a4f708.jpgm_342d796148ff45778ed73feb9f2803d5.jpg

Sucks! New Head is a definite right? I have seen one of your posts that you mentioned a head restore shop but do you think they would be able to help me out on this one? The Cylinder looks fine so I lucked out there, but a new piston and ring will definitely be going in with the new head. I already have a new cam chain on the way so that's good. Anything else besides gaskets and such you think I am going to need? Thanks for all he help. The crazy thing is that the bike has about 21hrs on it!!!!

If you're going to tell me that had compression, I'll be forced to laugh. :thinking:

But, yes, EDCo can fix that. Call them and arrange to send it out.

You got me on the compression. Not sure what I was feeling. Maybe it was just hopefull thinking. Thanks for the link and advise

good thread!

So what caused the failure?

I personally think that the Cam Chain was loose and the bike jumped time but don't quote me on that. When I bought it the guy had just had the valves checked by his mechanic. He said that the cam chain will need to be replaced soon but I will be fine for a while. I guess 4 rides and 3 hours was a little more than a while. The crazy thing was that the bike ran without a nitch of noise or warning... Then KAAAA-BOOOOMMMM. Thank god I just landed and was not on the face of a jump.

My new 450, just rode in.

The 2 exhaust cam's 0.02mm to small

1 of the 3 intake's 0.02mm to small.

Thats allready an explanation foor the decell fire's I guess

Thats allready an explanation foor the decell fire's I guess

No, it's not.

A certain amount of decel backfire from a YZ450 is entirely normal. If it pops off a few times during decel in an irregular manner, it's an indication that the pilot circuit is set up about right. It should do that some of the time, and sometimes not, depending on altitude and weather. If it's excessive, i.e. a steady stream of popping every time you back off, it's probably lean.

Tight intakes can cause a lean idle, but only when they are well below spec, and by the time they do that, they should be causing extreme hard cold starting, and a "hanging" idle.

Remember that excessive popping is very often caused by an air leak in the front half of the exhaust.

it was a new bike, no intake of air at the beginning of exhaust.

Ik thought if the valve adjustment is too bad, intake/exhaust are the same time open. We call it "valve overall". Normally a car is always running with a little bit of exhaust gas + new air/fuel mixture. In extreme situations, the fresh mixture can go in the exhaust.

Valve clearance would have to be very far off to alter valve timing to a significant degree, and both the intakes and exhausts are normally open for about 80 degrees as the engine goes over TDC at the end of the exhaust stroke as it is.

The most common place for an exhaust air leak is at the joint between the header and mid pipe.

I always put some "copper grease" on it.

It's protected up to 1100°c

I personally think that the Cam Chain was loose and the bike jumped time but don't quote me on that. When I bought it the guy had just had the valves checked by his mechanic. He said that the cam chain will need to be replaced soon but I will be fine for a while. I guess 4 rides and 3 hours was a little more than a while. The crazy thing was that the bike ran without a nitch of noise or warning... Then KAAAA-BOOOOMMMM. Thank god I just landed and was not on the face of a jump.

Man you're scaring me now, I better get a new cam chain for my used 450 before it happens to me.:-o

You read this one, then?

http://www.thumpertalk.com/forum/showthread.php?p=3150405#post3150405

It was written for an '05 or earlier model, so ignore the part about removing the stator plate.

Gray, good ref for cam chain replacement. I'm ordering a chain tomorrow AM, but I DON'T have a puller for flywheel . . . do you have a recommendation for a decent low-cost one, or do I have to order the actual factory Yamaha tool?

Thanks,

RD

If your YZF is '05 or before, it takes one puller, which happens to fit most Japanese MX 2-strokes too, and if it's '06 and up, it uses the same one as a CRF450. Either puller should be readily available at a good shop for $20 or so.

If it's a late model, you might look at this:

http://www.thumpertalk.com/forum/showthread.php?p=5462850#post5462850

If your YZF is '05 or before, it takes one puller, which happens to fit most Japanese MX 2-strokes too, and if it's '06 and up, it uses the same one as a CRF450. Either puller should be readily available at a good shop for $20 or so.

If it's a late model, you might look at this:

http://www.thumpertalk.com/forum/showthread.php?p=5462850#post5462850

Yes it is a late model . . . any year CRF450F? (I found one on Thumpertalk but it doesn't have a year noted)

Check listings at Motion Pro or somewhere. I believe they are all the same.

From Rocky Mountain

Tusk Flywheel Puller 24mm

Fits: 2008, YAMAHA, YZ450F

Regular: $19.99

Our price: $14.95

Part# 1179010001

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