Kz900 bent valves from not getting cams right

  • terry s
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Kz900 bent valves from not getting cams right

06 Jul 2019 08:38
#807055
I put rings in this 1976 kz900 and I guess I didn’t get the cams in time. Anyway I now have 2 intake valves bent. I replaced them and put cams in temporary to check valve lash.on the work bench. I used a nuway cutter for the valve seats. I took a small amount out to freshen them up. Put 2 new valves in.and lapped the valves in. I now have .406mm valve lash on one and .508 mm on the other. I did not grind the valve guide stem. Am I going to have enough of room in there to put bigger shims in there? I have 225mm in there now.

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Re: Kz900 bent valves from not getting cams right

06 Jul 2019 09:55 - 06 Jul 2019 09:56
#807062
If you cut the valve seat to deep with the Neway cutter the valve stem goes deeper into head. So the valve bucket get closer to the cam and now you have to use thinner shims!!! The Minimum shim size is 2,00 mm, so you will get 0,15 mm (.406 mm) and 0,25 mm (.508 mm) of valve clearence.
The (.508 mm) valve had to be grind off 0,15 mm and the (.406 mm) 0,050 mm on top of the stem to get 0,10 mm valve clearance.



Last edit: 06 Jul 2019 09:56 by Scirocco.

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  • VTEC
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Re: Kz900 bent valves from not getting cams right

06 Jul 2019 14:28 - 06 Jul 2019 15:02
#807077
Doesn't make sense. Grinding seats or valves will increase valve height and decrease valve clearance. Are they OEM valves?

Anyway, you need bigger shims to decrease clearance. The book shows the biggest shim is 3mm that go in .05mm increments, and you're off less than .5mm to reach desired spec at .075mm. (.10 - .05mm).

.508mm clearance with 2.25mm shim > use 2.70mm shim to get .058mm clearance or 2.65mm/.108mm
.406mm clearance with 2.25mm shim > use 2.60mm shim to get .056mm clearance or 2.55mm/.106mm

I'd personally go on the big side to play it safe.

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Last edit: 06 Jul 2019 15:02 by VTEC.

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Re: Kz900 bent valves from not getting cams right

06 Jul 2019 14:56
#807079
Pardon to my bad math, i had missunderstood something wrong, VTEC´s math is right.
But if so someone did a really bad valve adjustment Job before.....

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Re: Kz900 bent valves from not getting cams right

06 Jul 2019 15:24
#807082
Now I'm confused. :huh:
.406 Millimeter = 0.01598 Inch
Steve

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Re: Kz900 bent valves from not getting cams right

07 Jul 2019 06:58
#807113
SWest wrote: Now I'm confused. :huh:
.406 Millimeter = 0.01598 Inch
Steve

He's got .01598" clearance and it should be .003" . Needs a .01298" thicker shim to correct. Or close as possible.
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