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efan450f

05 yz 450 with tight cams please help

12 posts in this topic

if theres any one out there who could help that would be great. I bought an '05 yz 450 f used last year. i rode it a couple of times and brought it to dealer to have the valves checked and adjusted. they called me later and said that i had a cracked valve spring(exaust) and a cracked head. i am mechanically inclined but this is my first four stroke so i had them replace everthing for 1,100.00 plus tax. i asked what caused this damage they said from improper valve adjustment. so i've ridden the bike about 10-12 times since the rebuild and went to check my valves the other day. needless to say i've got about .090 on the exaust cam and my smallest feeler gauge.050 wont even fit under the intake cam. to make the situation even better i pulled off one of the cups (part that goes in between the cam and the valve shim) and the shim number is 85. the smallest shim listed in my yamaha service book 120. i called the dealer and they told my i probably need new valves. this may be true, but why so soon. when my head cracked the bike was still running great they checked and miked my cams for warp and stuff and said they were fine. do you think they could have cut my valve seats in the head to deep or is the valves sinking in to the head a common problem. should i cut the valve stem, put new valve seats in or what i don't want to ride with out the proper clearance and possibly cost my self a lot more money any suggestions would be appreciated. thanks everyone this web site rocks

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Dude that is absolutely crazy! &%$#@!?! They must have screwed you BIG time. There is no way that your bike could start breakin stuff that easily. (unless you ride the revlimitter everywhere)

Its a yamaha 4 stroke and they just dont go through top ends that fast. My '03 YZ450F is still going strong on the 5 year old top end.

Repost in the YZ450F forum and grayracer should be able to help you out.

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the increments are in metric im not sure on my readings im going from memory it was either .090 or .0090 i'll double check i will post again tomorrow either way it was way too small of a gap on both cams and whats up with the #85 shim is that even a yamaha part thank you to everyone who has replied with your input it makes me feel better knowing once i get this thing fixed properly i wont have to replace valves every couple months

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Well, the shim is almost certainly a 185, which is in the ball park of shims that the bike is likely to have been built with.

At .09mm, you need a 170 to correct that to .24mm.

I'd like to know:

How they determined it has a cracked valve spring, and where exactly the head is cracked.

Valve springs are cheap, and most things that happen to a YZ450 head can be repaired cheaper than the head can be replaced with new parts. The other thing is the wear you say you have on the valves doesn't sound good, and if your measurements are accurate, it's time to replace them.

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i will mike the shim to see how thick they are. as far as the gap goes i've got .009 on my exaust, and .005 is my smallest one and that wont fit under the intake cam. the cracked valve spring they showed me it was cracked on an exaust valve. the head was actually cracked on top where the cams sit right in between both cams the crack did not go all the way through to the combustion chamber but the mechanic said that the cams were grinding into the head making my valves so tight he could not get any gap. i wonder if he really checked my cam tolerances or just said they were okay or cut too much off the valve seat. if i check the shim thickness and if a 185 shim is the same as the "85" thats in there then i will just re-shim it accordingly but something in my gut says this is gonna cost me a lot more money. i will post back as soon as i check the shim thickness against my service book. thanks again for the help.btw if i have to put new valves in does any one suggest oem valves or aftermarket cost aside i want a better valve. thanks

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also the measurements i gave yesterday are not in mm

intake= less than .005"/.127mm

exuast=.009"/.229mm

these are right off my feeler gauge

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Guess what? Your exhaust valves are right on the money where they should be. Spec is .20-.25mm (.008-.010")

You need a .004" gauge to check your intakes. They should be .10-.15 mm (.004-.006), and they may be OK, too.

Now what about the valve spring and the crack?

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the valve spring and crack in the head were all replaced last year by the dealer so that crack is not an issue any more but since they told me it was cracked because of never having the valves adjusted so i want to stay on top of it so i don't have the same problem again.everything was replaced: head, all five valves,keepers,shims,all five springs,valve cups, valve guides the only thing reused were the cams and the timing chain. i hope the guy working on it knew what he was doing cause to top it all off i picked it up and rode it and it was smoking every time i slowed down... needless to say the guy didn't even check everything cause he didn't put the plug in my head where the manuel decompression lever went and yamaha doesn't show it as a part you can buy on microfiche. luckly i went there a week later and they still had my old head and sure enough the plug was sitting right in it! if i didn't notice the smoke and shut it off it could have cost me an engine! im glad to hear that the tolerances sound right im gonna ride it a couple more times and re check them just to see. thanks.

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Guess what? Your exhaust valves are right on the money where they should be. Spec is .20-.25mm (.008-.010")

Just the other day I checked my valve clearance for the first time after I rebuilt the top end and freaked when they all measured WAY tight...figured my valves were toast and was kicking myself for not replacing them along with everything else. Took a deep breath and restarted the measuring process to verify and that's when I realized that I was looking at the inch markings on my feeler gauges instead of the mm markings. Everything was perfectly within spec. Duh. :thumbsup:

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...he didn't put the plug in my head where the manuel decompression lever went and yamaha doesn't show it as a part you can buy on microfiche. l.... im glad to hear that the tolerances sound right im gonna ride it a couple more times and re check them just to see. thanks.
The plug, PN 90338-18004-00, is item #14 on the "Camshaft Chain" page of the parts catalog. But it's a piece of (stuff). The least little build up of crankcase pressure will blow it out. You're better off with one of these, or an 18mm brass cup plug (freeze plug).

Your intakes need to be checked with the right size gauge before you can say that they are OK. Get a .004" blade, or just buy a new set at an auto parts store for $3-4 or so.

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Efan,did you get your broken parts back??,or you just "Assumed" that parts

where damaged,and let them fix it?...never trust a dealer!

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