Help with a KZ750 spectre

  • JohnLuke
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  • 1982 KZ750N Spectre
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30 Mar 2018 09:46 #781012 by JohnLuke
Help with a KZ750 spectre was created by JohnLuke
Hey, I have been rebuilding a 1982 kz750 spectre and after grinding the valves to make them seal properly. Now 3 valve clearences are at 2.20mm and they can only get a 0.00-0.03mm shim under them. So that means I need to get a 2.05mm shim to get it back to the right clearence. But my question is when I get the bike back up and running will the valves seat and go deeper in the cylinder? If so, Idk what I’ll do because 2.05mm shim is the smallest Kawasaki makes. I have seen a old video on here that says you could get a perfessional machinist to grind the tip down so that you can get clearence back.

Is that what I’ll have to do?

Thanks!

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30 Mar 2018 12:09 #781019 by gordone
Replied by gordone on topic Help with a KZ750 spectre
I’m a newbe, but when I got my valve overhauled, I needed to tap of some metal on the valve to get enoufg clearness, after advise from other members here. I have been informed the valve clearness will be less after some miles when the top is overhauled.

1981 KZ650-D4, with 1981 z750L engine (Wiensco 810 big bore).

Project:
www.kzrider.com/forum/11-projects/607213...sr-1981-z750l-engine

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  • JohnLuke
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30 Mar 2018 12:40 #781020 by JohnLuke
Replied by JohnLuke on topic Help with a KZ750 spectre
That’s the thing. I don’t want there to be less clearence. To make things easier to understand. You’re saying as time goes on the “Gap” will be smaller. I need it to be “Bigger” /“Thicker’.

Thanks!

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30 Mar 2018 12:46 - 30 Mar 2018 13:09 #781021 by gordone
Replied by gordone on topic Help with a KZ750 spectre
You must make sure when you grind of the top, you have some clearness to the split keeper. The force from the cam. Shall not go into the split keeper.

Yes that what I have been told on my engine max. Valve clearness is 0,18 and 0,15 is good referance since the valve clearnees will be tighter in the start...

1981 KZ650-D4, with 1981 z750L engine (Wiensco 810 big bore).

Project:
www.kzrider.com/forum/11-projects/607213...sr-1981-z750l-engine
Last edit: 30 Mar 2018 13:09 by gordone.

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30 Mar 2018 14:59 #781027 by Nessism
Replied by Nessism on topic Help with a KZ750 spectre
Your machinist guy messed up. He should have ground a few thousands off the valve stems while performing the valve job. That moves you up the shim range and makes room for wear and tear in the future.
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  • SWest
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30 Mar 2018 16:53 #781033 by SWest
Replied by SWest on topic Help with a KZ750 spectre
If I remember correctly 0.012 (0.3) mm is the max that can be "tipped" on the valve stems.
Steve

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  • Scirocco
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30 Mar 2018 17:27 - 30 Mar 2018 17:31 #781037 by Scirocco
Replied by Scirocco on topic Help with a KZ750 spectre
The law for every 3 angle valve job is = less is more.
2-3 turns with a NEWAY valve seat cutter on a valve seat ring is more you need to resurface
the leak between the valve/seat surface.
I have to renew all my valve seat rings in my head a decade ago. My shim size is now 2,70 - 3,20 mm.


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Last edit: 30 Mar 2018 17:31 by Scirocco.

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30 Mar 2018 20:10 #781051 by cb900f
Replied by cb900f on topic Help with a KZ750 spectre
For Kawasaki's you used to be able to get a valve gauge that fits over the valve stem when inserted in it's guide. If the valve protrudes above the surface of the gauge, it needs to be trimmed. If it's below, it might (but probably not) need a bit more seat work.

As mentioned above, the amount of valve available for trimming is limited as you run into problems with the keeper grove not being far enough away from the end of the valve. I remember when you could buy valves (for cars) that didn't have a keeper groove - the valve was trimmed to length first, then the groove was cut in the valve.

If the valve is too long, the option are to go to an ovesize valve which will locate lower in the head or install new seats (if that's an option).

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30 Mar 2018 20:12 - 30 Mar 2018 20:13 #781052 by cb900f
Replied by cb900f on topic Help with a KZ750 spectre
Here's a valve height gauge: racetoolz.com/

Last edit: 30 Mar 2018 20:13 by cb900f.

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  • JohnLuke
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30 Mar 2018 21:45 #781056 by JohnLuke
Replied by JohnLuke on topic Help with a KZ750 spectre
So are yall saying I’m screwed? Do I need to buy a new head? I know one place that sells shims smaller. Like 1.85mm+ shims. The site is called Dennis Kirk. Is that a trust worthy site? And if I get some, will the valves just run in the head on start up and decrease the clearence again. I’ll need to reshim them again and then I’ll be really screwed.


Thanks!

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31 Mar 2018 05:50 #781060 by Nessism
Replied by Nessism on topic Help with a KZ750 spectre
Dennis Kirk is a reliable source.

The factory shims go down to 2.0mm. With mileage the clearance will reduce so its important to have some room for wear. I'm not sure about those 1.85 jobbies. It's important that the shims stick up above the retainer they sit in and I'm not sure if 1.85 is tall enough.

Personally, I'd pull the head back off and take it back to your machinist guy and tell him to remove the valves and use his grinding machine to take a few thousand's off the stems and then reinstall them back. That will move you up the shim range. Check the chart in your manual to get your head around how much should be removed.

Good luck

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  • SWest
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31 Mar 2018 06:34 #781062 by SWest
Replied by SWest on topic Help with a KZ750 spectre
I plan on taking 0.008 off each valve giving me 4 more adjustments each. That should last a long time. I'll be able to use the larger shims I have in my collection.
Steve

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