yzf 450 valve clearance???

Hi, just been checking my valve clearances on my 04 yzf 450 and they seem to be a little out compaired to the manual

the engine has had a full re-build and been run for 4 hours max

Exhaust are both 0.254mm (0.010") spec 0.20-0.25mm (0.0079-0.0098")

so just on max should i re-shim?

Inlet are, left 0.152mm (0.006") middle 0.254mm (0.010") right 0.0229mm


spec 0.10-0.15mm (0.0039-0.0059")

theres a fair bit of difference on the inlet side, would this cause any affect to the bikes running or risk damaging the motor?

This is my first time of checking valve clearances as i'm pretty new to four strokes and not 100% cluded up for how to go about re-setting timing if i go and take cam's out

So any advice/ help would be very much appreciated!

Thanks in advance Gary

You need to recheck. For one thing, it's very odd that the clearance at the center is larger than spec, and for the other, your numbers don't line up on the right. .0229mm would be extremely tight. If it's actually .229mm, that's loose again.

hi thanks for the quick response, inlet right should be 0.229 typo!

Could it be that the guy who done the motor set them up loose? I thought that valves would stretch making clearances go tighter, is it a big issue them being a little loose compaired to being tight?


Normally, valves and seats wear at their mating surfaces, so the valves move upward into the head, making them tighter. Loose valves would be due to some other wear condition, perhaps damaged cam saddle caps, or to incorrect set up.

Thanks again, i will get on to the guy that built up the motor and ask what clearances they were set up to


You can ask him that, but given that the intakes are out of spec in two of three places, you'll need to correct them anyway. The fact that one is right and the other two not would suggest that he's going to say he set them to the right specs whetheer he really did or not.

Also, I have no idea how much experience you have, but you should know that you can force a feeler gauge under a cam that's bigger than the actual gap, so be careful that you're not doing that.

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