Stuck exhaust valve shim yz426


11 replies to this topic
  • STL450rider

Posted December 27, 2011 - 12:49 PM

#1

Im in the process of shimming my yz426, and i got all shims out except for the exhaust valve shim(the one that sits under the decompresison lever). Any tips to get this out? Ive tried a magnet and a pick and still no luck. Looks like the previous owner tried to pick at it a little bit and left it in. Both exhaust valves had the original shims but all of the intakes were hot cams shims. Im guessing he had this problem and just left it. The one exhaust valve was still in tolerance (.010 and it calls for .010-.012), the other one thats stuck is at .008 so its a little bit off. Any help would be appreciated, thanks. :bonk:

  • 2grimjim

Posted December 27, 2011 - 12:54 PM

#2

You can try to use a brass punch and gently tap on the retainer.

  • STL450rider

Posted December 27, 2011 - 01:13 PM

#3

tried it, still nothing, i tried using a socket too. its stuck in there pretty good

  • 2grimjim

Posted December 27, 2011 - 01:25 PM

#4

You can keep riding it the way it is, or pull the head.

  • 2grimjim

Posted December 27, 2011 - 01:33 PM

#5

You could roll the engine to TDC, put a socket on an long extension, and push the retainer down 'till the valve contacts the piston. This will push the stem up enough to pop out the shim, BUT is verry risky. If you push too far and the locks fall out, you're screwed and have to remove the head. You also don't want to put any bending load on the velve stem either. If you bend the stem, you'll be pulling the head for that too.

I have done this trick before, but I normally don't advise people to use it.

  • STL450rider

Posted December 27, 2011 - 02:35 PM

#6

sounds like all of my options are risky besides pulling the head, which im going to use as a last resort since it has a brand new head gasket. how about drilling a small "slot" into the shim so i have a groove to get ahold of so I can tap it loose? seems less risky damaging a shim that already needs replaced than possibly bending a valve to me

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  • 2grimjim

Posted December 27, 2011 - 03:23 PM

#7

sounds like all of my options are risky besides pulling the head, which im going to use as a last resort since it has a brand new head gasket. how about drilling a small "slot" into the shim so i have a groove to get ahold of so I can tap it loose? seems less risky damaging a shim that already needs replaced than possibly bending a valve to me


A drill bit (unless it's a tungsten carbide bit) won't touch the shim since it's hardened and if you do mange to drill through, you'd also drill into the valve stem, locks, or retainer. Not something you want.

Try the socket/extension trick and if you pop the locks out, you still haven't damaged anything.

  • STL450rider

Posted December 27, 2011 - 03:30 PM

#8

Got the mother f'er.. 3 hours later, every method possible and a lot of cursing, popped right out ha.

  • 2grimjim

Posted December 27, 2011 - 03:48 PM

#9

Got the mother f'er.. 3 hours later, every method possible and a lot of cursing, popped right out ha.


So..how'd you get 'er done?

  • STL450rider

Posted December 27, 2011 - 04:31 PM

#10

Tapped with a socket, used a pick, tapped around the spring with a punch and eventually got it out with the magnet.. One other question for ya.. When reshimming, should I shoot for the higher end of the tolerances because wont they expand a hair?( I.e.- intakes call for .006-.008, so should I make them closer too .008 rather than .006? Or does
It matter?

  • grayracer513

Posted December 27, 2011 - 05:52 PM

#11

The entire range is only .002, so no, it doesn't matter that much, but ideally, you set them toward the tight side if you can, because it's easier on the valve train. Yamaha sets them all at the low limit using shims available only to them in .01mm increments. Anything within the specified range is acceptable, though.

  • XCF4fity

Posted June 04, 2012 - 04:26 PM

#12

I was reading this because I had the same issue. I managed to get it fairly quickly once I got a sharp tipped nail punch and started gently working the slightly raised lip on mine, starting at like a 45 degree angle down and sllightly off center to try to spin it. Later I took the angle down almost sideways as the lip got bigger. It just started rising a little at a time. Probably not the safest approach, but the mother fluffer came out.





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