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charger01

My 2007 YZ450 Valve Report

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I bought a brand new 07 YZ450 a couple months ago and have put 8 hours on it and decided to check the valves yesterday. After reading all the posts in this forum about how hardly anyone has had to adjust them, I was very surprised to find that my exhaust valves were out of spec to the tight side, they measured .17mm to be exact. I reshimmed to within spec and will check the clearance again in another 8 or 10 hours. Hopefully they will still be in spec. Not sure why I am one of the few that has had to adjust the valve clearance. I changed the oil and filter right after break-in and then again after 3 hours. This is the first yamaha i've owned in about 5 years. I've had 4 different CRF450s and have never had to adjust the valves on any of them(except for 1 tight exhaust valve after the break-in on an 06) . Other than the valves I really love the YZ. Power is great and handling is so much better than the crf IMO. I can throw it around so much easier and it doesn't tire me out as fast as the crf did. As long as I don't experience any valve issues I will be very happy with the switch I made. :applause:

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It's worthwhile to look at how you measured them to be .17mm. There is no direct English equivalent to this metric increment, which is .0069", and the nearest English gauge is .007". .008" is very near exactly .20mm, so you see how small the difference really is, and what tolerances you're working with. Also remember that feeler gauges are by their nature, a device that requires a lot of subjective judgment on the part of the user, and I very often find that I don't get the same measurement as a less experienced individual does on the same assembly.

Also, Yamaha builds these engines to as close to the low end of the clearance spec as they can, and they use .01mm shims to do it. Since both valves were the same, my first guess is that they were built exactly like you found them, and that you measured wrong. Or, it could have been an error in reading or setting up the fixture they use at the factory to gauge the the valve shim selection. Check again in a little while, and see what they're doing. I think you're OK, but I'd have to see it to be sure.

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Hi grayracer513,

This is how I measured the clearance. First I tried with the .20mm feeler and it wouldn't slide in no matter how hard I tried. Next I went to the next smaller feeler which was .18mm. It fit, but was pretty tight. Next I used a .14mm and a .03mm feeler and put them together and slid them in. That resistance felt about right. After I reshimmed, the .20mm slid in and felt about right. Does this sound like I measured right? Thanks.

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It's worthwhile to look at how you measured them to be .17mm. There is no direct English equivalent to this metric increment, which is .0069", and the nearest English gauge is .007". .008" is very near exactly .20mm, so you see how small the difference really is, and what tolerances you're working with. Also remember that feeler gauges are by their nature, a device that requires a lot of subjective judgment on the part of the user, and I very often find that I don't get the same measurement as a less experienced individual does on the same assembly.

Also, Yamaha builds these engines to as close to the low end of the clearance spec as they can, and they use .01mm shims to do it. Since both valves were the same, my first guess is that they were built exactly like you found them, and that you measured wrong. Or, it could have been an error in reading or setting up the fixture they use at the factory to gauge the the valve shim selection. Check again in a little while, and see what they're doing. I think you're OK, but I'd have to see it to be sure.

I think this is a topic that gets a lot of different answers too.You could have 10 people measure the same thing and more than likely get at least 5 different answers to.Believe me i have seen it!Good post grey.Moral of this make sure you are right before you shim.:applause:

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I'm just hoping that since it looks like I'm about the only one on this forum that has had the valves be out of spec this soon that I don't run into valve problems on this bike. Hopefully they just shimmed the exhaust valves too tight from the factory. And there is NO doubt that they were tight....cause when you can't even fit a .20mm feeler(which is minimum spec on the tight side) then that leaves no doubt they are out of spec on the tight side. I'll give another update after I put a few more hours on the bike. Hopefully I report good news!! :applause:

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mine were out of spec when I checked them after 3 hrs of break-in and they were on the tight end of the spec. so I re-shimmed and at 20hrs they were still where I put them. I have 52hrs now, I am going to check them today after I go riding and probably put 4 more hrs on. The bike still starts fine though, so I am thinking they are still good.

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I only have about 6 hours on mine.Although i know i should check them,i dont want to untill it gets hard to start.Does this make me a bad person?

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I only have about 6 hours on mine.Although i know i should check them,i dont want to untill it gets hard to start.Does this make me a bad person?

it makes you a horrible person :applause: . At least check them now after break in.

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I only have about 6 hours on mine.Although i know i should check them,i dont want to untill it gets hard to start.Does this make me a bad person?

It doesn't make you a bad person, but it may make you a poorer person if you have to spend big bucks after you lose a valve, by hitting the piston or breaking one off. Remember the old fram oil filter sloagn. "You can pay me now,or pay me later". It is your choice. Good luck! :applause:

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Im having some similar issues, well worry.

This is my first 4stroke and i have just checked the valves at about 7hours and the intake where fine but the exhaust looked a little tight. Well the 0.20mm gauge would fit in but was very tight.

Is it worth reshimming so that it is middle of the spec or will this be ok and just keep checking???

Also i think my jetting has been a little lean could this be a cause???

Thanks

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My friend ran into the same issue. He bought an 06' new approx 4 months ago and we checked the valves a couple weeks back and he had 2-intake and 2-exhaust out of spec. I just figured every now and then a few of the yz's will need adjustment after break in. Most the people that post on here claim that even after a year they have not had to adjust theirs. The lack of valve issues is whats drawing me into buying the yamaha because I got tired of having my honda adjusted 4-5 times a year. Is this just a break it in, adjust and your good for a year thing or do yamahas still need adjustment periodicaly?

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I think the key would be to check them off the showroom floor, then after break-in (around 10 or so hours) and then if you are concerned every 15-25 hours. I have over 75 hours on mine ('05) with no need for adjustments at all....

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