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TOPIC: Cam Caps must match head - why?

Cam Caps must match head - why? 24 Aug 2014 22:38 #645041

  • RobK
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Was hoping the rather impressive collection of Z/KZ folks and knowledge here could help me get to the bottom of something that's been bothering me.

Conventional wisdom dictates that cam caps are line bored with the head and MUST match. You can't just grab any random set of caps and put them on any random head.

OK, that makes sense on the surface, but when I think about the mechanics of the "why" I realize I don't really understand precisely where the variations exist.

First off, we can assume that Kawasaki was using jigs and such, inline with large scale manufacturing (they ain't called Kawasaki Heavy Industries for nothing), so deviations should, at least in theory, be very minor.

Major enough to cause pre-mature shell bearing wear, goes the retort. OK, I get that.

However, if we're looking at the cam on the head, we can likely assume that any deviation on the Y-axis relative to the floor of the head (at least strictly along the vertical axis) will be immaterial as the head itself sets the height of the cams. As long as the split truly is a bisect, it doesn't really matter if the cams are 0.1mm higher in one head than another. The tensioner takes care of that problem.

So perhaps the "split" of the bore could be a source of this variation. Essentially if the bore isn't perfectly bisected by the split, this would, in effect, change the size of the bore if you used unmatched caps and head. So instead of the machine cutting 50% from the top of the bore (cover) and 50% from bottom (the head), it's cut maybe 50.5% and 49.5%, (or some other deviation). Binding and/or slop would result, I would think.

Seemed time to started playing around with some old parts to see if they could reveal the answer.

I have this huge bag of random cam covers I got when I bought a big lot of Z1, KZ900, and KZ1000 bikes and parts. There are all manor of styles and years in there, so figured it was a good source of data to test.

So I pulled a bunch of them out and started measuring the distance from the top of the bore, to the bottom of the cap. The differences seemed difficult to detect, at least with my digital vernier. They seemed to all be the same, regardless of style.

There is also the possibility that the "split" isn't really horizontal relative to the head. This seems a candidate, but would also seem to point at some pretty sloppy machining, something I've not really seen a lot of in the 10 or so Kawas I've owned. Still, a possibility.

Moving to the X-axis, this is potentially where we could get in real trouble. If the bore is not quite centered between the bolts from one head to the next, and we mixed caps and heads, then we have an offset left-to-right between head and the cap, and there is no doubt this would cause premature shell wear and maybe worse.

So I grabbed a Z1 head off the shelf and started test fitting caps. As long as the cap number corresponded to the position on the head, they seems to line up correctly.

Again, this was a "by eye" test, so perhaps I missed something.

Assuming that there are indeed important differences that my observations and/or tools were too crude to detect, (a very real possibility), wouldn't coming up with a method for lapping the shells be simpler than milling the head, as is normally prescribed? A few years back I had to replace cam bushings on a Triumph 650 and the bronze had to be bored/lapped to fit. Why not do the same on the Kawa 4? Can't say I know exactly how one would do that off the top of my head, but certainly seems more straight-forward than finding the (likely uncommon) machine shop that could mill the head.

This is more of an academic question than anything else, but if someone out there can help me understand the subtleties of this, I would be very appreciative.

In the meantime, I'm going to go start playing around with the cams, heads and covers I have and see how much slop and/or binding I can create by mixing and matching.

Thanks, all.
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Last edit: by RobK.

Re:Re: Cam Caps must match head - why? 24 Aug 2014 23:30 #645042

  • Tomolu5
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I have little of value to offer, and I will be watching this one closely

It is true that there is too much slop in digital veneers, and a micrometer will be more accurate.

I have also seen several members here, guys that have been around a while, say that you can mix and match to your hearts content. I have also seen an equal or greater number of post saying otherwise.

Personally I would not chuck an otherwise good head over the can caps. If I had to mix caps, I would measure to make sure the hole is round, and plasti-guage in several spots. If all those numbers jived, I would bolt it down and go with it.

I would bet a dollar or two that there are engines thrown together with far less care out there that run just fine.
Mine:
04 Honda rebel 250(wifes)
04 GSXR 750(bolt on galore)
98 CBR 600F3(filter, pipe, adjustable cam sprokets, dyno tune)
76 KZ900A (LTD gauge pods, crash bars, LTD(style)pipes, dyna coils and ignition,headwork and mild port cleanup by cavanaugh racing, K&N filter pods, heck I dunno.

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Cam Caps must match head - why? 25 Aug 2014 05:15 #645049

  • 4TheKZ1000
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The way I understand a common complaint :

When the factory machines the head, the cam caps are assembled to the head.

The head is then set up in a jig and the cam caps / cam journals are then "Line bored"

This creates a perfectly straight and true hole that is unique to this particular head.

So, If you use a cam cap from another engines head ....... is it a match or fit??? or is it measurably off??? how many machines are line boring heads and are they of the same quality???

This is one of the complaints about swapping the cam caps. I have no opinion either way.

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Last edit: by 4TheKZ1000.

Cam Caps must match head - why? 25 Aug 2014 05:19 #645050

  • PLUMMEN
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You can swap bearing caps,all it takes is a bucket full of spare caps and some plasti gauge to make sure clearances are close.
Its not ideal,but can be done. ;)
Still recovering,some days are better than others.

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Cam Caps must match head - why? 25 Aug 2014 06:04 #645052

  • 650ed
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One other thing to consider is that not all KZ heads use cam bushings. For example, the KZ650 cams sit directly in the head/cam cap bore. Ed
1977 KZ650-C1 Original Owner - Stock (with additional invisible FIAMM horn)
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Cam Caps must match head - why? 25 Aug 2014 08:13 #645063

  • loudhvx
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One time someone sold me two heads and a bag full of caps (just enough for the two heads). It was not difficult to figure out which cap came from which head. It took some time swapping caps back and forth (50/50 chance), but when the cap was from the wrong head, I could feel the ridge in the bearing surface. I could not see it, and didn't bother measuring it, but by feel, it was very clear.

This was on a 550.

I don't think I would have been able to tell the difference if the caps came from some unrelated heads. When it was wrong, it felt close, but only when comparing directly against the correct matched set, could I tell the difference.

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Last edit: by loudhvx.

Cam Caps must match head - why? 25 Aug 2014 10:17 #645081

  • steell
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I don't know what tools you're using, but it would be simple to determine proper fit using a bore gage. A t handle snap gage should work also, and be a lot cheaper than the bore gage, as bore gages are specific over a limited range.

In manufacturing, everything is done to a tolerance, as in + or - , so it is possible to have a tolerance stack that exceeds the limits that can be repaired by replacing one part in the stack. So you will have x number of caps that fit along with y number that won't.
KD9JUR

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Cam Caps must match head - why? 25 Aug 2014 10:44 #645086

  • loudhvx
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In my case, it was only a matter of the right one versus the wrong one. But in a general case, where the caps are completely foreign to the head, there are so many ways the cap could be wrong. It's not only about how the bore was drilled, but how the cap mates to the head. If that surface is not perfectly square to the head, the cap can sit at an angle. The bearing surfaces joint can be smooth, but the bearing surface would sort of be cone shaped rather than a cylinder (head axis not coincident with the cap axis). It could also be that within some tolerance, as Steel said, the single bearing surface checks ok, but it may not be in line with the other bearings. Line-boring with caps in place, theoretically gets rid of all of these variables to some satisfactory degree.

However, that said, if you can get a cap that fits and the bearing surface checks out ok, and you can test-spin a camshaft to see there is no binding (valves removed), then it's worth a try, unless the camshaft is super valuable.

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Last edit: by loudhvx.

Cam Caps must match head - why? 25 Aug 2014 16:21 #645129

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The issue is bearing crush as that is what hold's the bearing from spinning in the bore.

On any plain bearing be it a cam bearing or a main bearing the o/d of the
bearing is larger then the i/d of the bearing jourrnal bore.
If this is to loose the bearing will spin and if to tight there will not be
correct clearance.
If the bore is not perfectly round it will distort the bearing and cause high and low
spot's at the bearing surface and cause metal to metal contact.
1980 KZ650 F1
ZX750A1 motor.
Wiseco 810cc kit.
Zukiworks racing ported head.
VM 29 smooth bore's.
Dyna 2000 Ign. w/Dyna mini coil's
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APE valve spring's.
APE Track King clutch.
V/H KZ1000 sidewinder.
3.5x18 laced to a KZ1000 disk hub.
150/60/18 Shinko 006 Podium.
63"...

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Cam Caps must match head - why? 25 Aug 2014 18:20 #645137

  • LarryC
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You can make any Kz 900/1000/1100 cap fit any other head. It's simple.... I've done it many times over the years.
It takes a little common sense and some patience....

If you want to know how...call and I'll explain it but I'm not about to debate it on the Internet. Trust me, it's as simple as tying your shoes.... You can do that...right???? :woohoo:

People make a great big deal out of simple things ...I've had my fill of it.. T.YV.M.

There's one thing that cam needs to be able to do.... .SPIN...as easily as possible without jumping up & down. Think about it... and ZukDave has pointed out the key factor in getting it right....Good on you Dave ;)
Larry C.
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Last edit: by LarryC.

Cam Caps must match head - why? 25 Aug 2014 19:04 #645145

  • gearheadmm
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SCRRREEEEEEEEEECH THUD! (thud was the engine locking up after about 2 mins running)
That's the sound a Neon makes when the cam clearance is too tight. No bearings.
Turbo install, with pistons and rods, customer sends head, forget why,
with broken cap replaced with one from the junkyard.
Neglects TO TELL ANYONE!
Thought it would be OK.
Cam cleaned up.
Please send new head.

LarryC wrote: You can make any Kz 900/1000/1100 cap fit any other head. It's simple.... I've done it many times over the years.
It takes a little common sense and some patience....

If you want to know how...call and I'll explain it but I'm not about to debate it on the Internet. Trust me, it's as simple as tying your shoes.... You can do that...right???? :woohoo:

I'm dieing to know!!!
Teach me something I didn't know, PM me.
I got a nice J head missing a cap I might need some day.
I've seen it done with a large assortment to choose from.
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Cam Caps must match head - why? 26 Aug 2014 06:36 #645197

  • LarryC
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gearheadmm wrote: SCRRREEEEEEEEEECH THUD! (thud was the engine locking up after about 2 mins running)
That's the sound a Neon makes when the cam clearance is too tight. No bearings.
Turbo install, with pistons and rods, customer sends head, forget why,
with broken cap replaced with one from the junkyard.
Neglects TO TELL ANYONE!
Thought it would be OK.
Cam cleaned up.
Please send new head.

LarryC wrote: You can make any Kz 900/1000/1100 cap fit any other head. It's simple.... I've done it many times over the years.
It takes a little common sense and some patience....

If you want to know how...call and I'll explain it but I'm not about to debate it on the Internet. Trust me, it's as simple as tying your shoes.... You can do that...right???? :woohoo:

I'm dieing to know!!!
Teach me something I didn't know, PM me.
I got a nice J head missing a cap I might need some day.
I've seen it done with a large assortment to choose from.


That's why you never take anything for granted that a customer brings to you. Check everything. Cams should be installed with no valves in the head. Spin them, wiggle them, check them with plastiguage. You first have to know the head if not warped. If it is you'll feel that the second you go to turn the cam.
Larry C.
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Cam Caps must match head - why? 26 Aug 2014 08:54 #645225

  • Kapahulu
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Good to know, I would have thought Larry C would say to never switch caps. If the situation ever presents itself I'll give Larry a call.

Thanks!
1978 KZ1000, 1976 KZ900, 1975 H2, 1973 H1, 1973 H2, 1978 RD400, 1977 RD400, 1974 RD350
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Cam Caps must match head - why? 26 Aug 2014 10:51 #645236

  • RobK
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Wow, thought I might get a reply or two, but pretty blown away, here.

Thanks, all for the replies. Some great info.

I wouldn't ever button up and start a motor without testing the movement/play/tolerances of...everything, especially big expensive bits that will spin really really fast. Experience has made me paranoid, which is likely a good thing.

Apparently Henry Kissinger once said (about Nixon), "You are not paranoid if everyone really is out to get you."

Don't really think a machine is out to get me, but Murphy makes sure the one thing you don't check will be the thing that will bite you in the buttocks.

I just took ownership of a '74 H2 that's been in a barn for 30 years. 15k on the clock and all original. Engine was lightly stuck which I was able to free up with just a little coaxing, and I am freaking dying to start the mother, and hear that ring ding, but know that I got to some things to do first, like clean the carbs, pull the heads and clean and check the cylinders, check oil pump functionality, etc etc.

Teaches you patience this wrenching malarky...

On the cam question, I do in fact have a Z1 engine build in the near future so the question is less academic as I realized the head doesn't have the caps on it (bought it apart). Glad I have that big bag of caps.

I'll post my results here.
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Cam Caps must match head - why? 26 Aug 2014 11:34 #645238

  • steell
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What Larry C tends to forget is that the answer you get depends on the skill set of the person answering the question.

Larry C answers as the guy that works on heads.
steell answers as the guy that works with metals.
Others answer with whatever level of experience they possess.

Different strokes from different folks :P
KD9JUR

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Cam Caps must match head - why? 26 Aug 2014 20:07 #645312

  • gearheadmm
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LarryC wrote: That's why you never take anything for granted that a customer brings to you. Check everything. Cams should be installed with no valves in the head. Spin them, wiggle them, check them with plastiguage. You first have to know the head if not warped. If it is you'll feel that the second you go to turn the cam.

In a perfect world...
YOU are in control.
Did I mention the dam thing locked up at 4:45 on a friday, had to be delivered, money was not in the job, AND...
I was not in control!
As any mechanic not in control will tell you...
My KZ runs.
PM me that trick Larry!
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Cam Caps must match head - why? 27 Aug 2014 05:15 #645337

  • LarryC
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steell wrote: What Larry C tends to forget is that the answer you get depends on the skill set of the person answering the question.

Larry C answers as the guy that works on heads.
steell answers as the guy that works with metals.
Others answer with whatever level of experience they possess.

Different strokes from different folks :P


dunno....common sense is common sense no matter what skill set it's applied to. That's precisely what's missing in today's modern society & people sure as hell aren't going to get it from a public school system ;) ...research "common core"
Larry C.

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Cam Caps must match head - why? 27 Aug 2014 05:17 #645338

  • LarryC
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gearheadmm wrote:

LarryC wrote: That's why you never take anything for granted that a customer brings to you. Check everything. Cams should be installed with no valves in the head. Spin them, wiggle them, check them with plastiguage. You first have to know the head if not warped. If it is you'll feel that the second you go to turn the cam.

In a perfect world...
YOU are in control.
Did I mention the dam thing locked up at 4:45 on a friday, had to be delivered, money was not in the job, AND...
I was not in control!
As any mechanic not in control will tell you...
My KZ runs.
PM me that trick Larry!


I hear you.... every once in a while we all get bit. It's usually when we take something for granted or think common sense is common... :silly:

A long, long time ago I was working on my Ski-doo Blizzard 7500 clutch. I thought there was too much play in the sliding half bushing. So off I went to the dealer to get a new one. I took the old one with me to be sure I got the right part. The mechanic there was very experienced and I trusted him. He looked at it, wiggled the sliding half on the shaft and said. "Larry....you're looking too close" I could sell you a new one but after the first couple or rides it will be exactly like this one. It's just the way they are and it won't hurt a thing.

I never forgot that and have used that line of thought often over the years....It applies here with regard to many discussions I've seen on the Internet regarding cam caps and especially cam bearings.... you can look too close at something sometimes....and then again...sometimes not close enough :lol:
Larry C.
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Last edit: by LarryC.

Cam Caps must match head - why? 28 Aug 2014 07:22 #645464

  • steell
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I prefer "Ain't got the sense God gave a goose" to "Lacking common sense" :P
KD9JUR

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Cam Caps must match head - why? 02 Sep 2014 06:01 #645891

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The cap are matched and numbered , like crankcases they are line bored. Cam journal bearings are quite lowly stressed (I think) compared to other engine bearings so I think the tolerance would be a little wider. In my misspent youth I even did 200 miles with one cam bolt broken.

Years ago I had a heap of old gpz bits, some already dismantled including two cylinder heads and a bag of caps. I removed the valves and torqued down the caps, one at a time, rotating the cam and feeling how smooth it was, A few were definitely wrong and you could feel it pinch up. After that I dot punched the caps to differentiate them.

(I always replace the m6 bolts with new high tensile steel and tighten by feel- had too many of these break or strip the thread.)
1980 Gpz550 D1, 1981 GPz550 D1. 1982 GPz750R1. 1983 z1000R R2. all four aces

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