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Cam bearing clearance 04 Oct 2021 15:32 #856185

  • Southpaw
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Hello All,

Decided to start a new topic. My last topic Spocket Ratio I found I was losing horsepower and wiped out set of cam bearings.

So the next episode, I sent the head to FBG for valve job, bought a used cam and used bearings( not matched set). Got the back today. Removed the valves and plastigaged the cam. Getting .001 or less and cam is very tight. My first thought is put the cam on a lathe and polish off  .001 to.0015. Any thoughts good or bad idea?

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Cam bearing clearance 04 Oct 2021 15:58 #856187

  • zed1015
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Very unusual for a cam to be tight especially with a used one ( unless it's bent so check that first ).
If the cam is straight i'd be looking at the cam caps to see if they are the ones belonging to the head.
If they've had a replacement cap or two that will cause the binding.
Check the bore for concentricity and if it's out that's where you need to rectify the issue.
 

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Cam bearing clearance 04 Oct 2021 16:11 #856188

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Zed, the cam caps are original. I'll check for  bent cam

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Cam bearing clearance 04 Oct 2021 16:38 #856191

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.001-006" Check if the cam is being pinched by the #1  and #3 cap. It's easy to do. You could use a small hone to make more clearance if needed.
Steve
Z1b1000 1975 Z1b
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kzrider.com/forum/11-projects/598262-kz-...-will-it-live#672882
kzrider.com/forum/2-engine/597654-poser?start=240#704229

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Cam bearing clearance 04 Oct 2021 16:47 #856192

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Swest,
I did make sure the cam had movement side to side before torqueing the caps , is that what you mean by pinched??
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Cam bearing clearance 04 Oct 2021 17:28 #856194

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Yes. Are the valves out while you're checking?
Steve
Z1b1000 1975 Z1b
Opinions expressed by me do not reflect those of the the staff or members
kzrider.com/forum/11-projects/598262-kz-...-will-it-live#672882
kzrider.com/forum/2-engine/597654-poser?start=240#704229

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Cam bearing clearance 04 Oct 2021 18:07 #856196

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You might want to torque the head down using an old head gasket and then measure again.  A small twist or bow in the head will throw the cam bores out of alignment, but tightening the head flat again will reduce the misalignment.

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Cam bearing clearance 04 Oct 2021 19:45 #856198

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Good point or you can use a striate edge across the combustion chambers to see if it's warped.
Steve
Z1b1000 1975 Z1b
Opinions expressed by me do not reflect those of the the staff or members
kzrider.com/forum/11-projects/598262-kz-...-will-it-live#672882
kzrider.com/forum/2-engine/597654-poser?start=240#704229

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Cam bearing clearance 05 Oct 2021 03:10 #856200

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FBG skimmed the head while they had it. Yes the valves are out. This is on the exhaust side I haven't checked the intake side yet

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Cam bearing clearance 05 Oct 2021 05:45 #856203

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Checked the cam between centers this morning there is .002-.0022 of run out, doesn't seem horrible but not great either . Is there a specific for that does anyone know?

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Cam bearing clearance 05 Oct 2021 06:55 #856206

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The factory service manual shows the process and specs for measuring the cam.  I've scanned the page from the '76 KZ900 manual.  The specs are the same in the KZ1000 manual, but the kz900 manual gives both inch and mm units. 

 
'78 Z1-R in blue, '78 Z1-R in black, '78 Z1-R in pieces
'95 GPZ1100 (sold) , '00 ZRX1100
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Cam bearing clearance 05 Oct 2021 08:07 #856211

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Was it just the one cam that chewed it's shells or both ?
If it's just the one then drop in the other cam in it's place and see if you get the correct clearances etc.
If you do you can probably rule out the head or caps and either aquire another good cam or true up the one you have.

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