TOPIC:

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!

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.

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

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!

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

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"

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...

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

I prefer "Ain't got the sense God gave a goose" to "Lacking common sense"

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.)

So what's the solution. I've got a mixed set of caps and head.

Caps are cut originally to fit the particular head they are on. Using a cap from a different engine could result in a misfit. That said, "Must" is probably too strong a term. I once mistakenly reversed #3 and 4 caps and ran the bike for an entire summer....only discovering my mistake when I checked the valves during routine maintenance the following winter. There were no issues. My thought....put the non stock caps on but check the bearing clearances to ensure they are adequate.

On a slightly different point, I've often wondered why KHI didn't install threaded steel inserts in the cam bolt holes to eliminate stripping the threads during installation.

They didn't think these bikes would be around as long as they are. They decided to build bikes that couldn't be rebuilt as easy as the larger fours. Now they're going to reproduce heads and other parts? Hmmmmmm.
Gotta give them credit for a job well done whether they like it or not.
Steve

Kawboy3 wrote: So what's the solution. I've got a mixed set of caps and head.

Drop the cam in the head with no valves or springs fitted and preferably use new shells for maximum accuracy and ideally arm yourself with some plastigauge and an internal bore gauge.
Do one cap at a time starting with matching numbered caps ( 1 in 1 etc ) and slowly tighten the bolts.
If the cap nips the cam try another cap until you find one that tightens and the cam still spins.
Repeat for the other caps.
Remember that caps 1 and 3 govern cam end float so you can only use 1's and 3's on the left side of the head.
There are steps that can be taken to ease off a tight cap and it's 50% common sense and 50% mechanical aptitude and if a person has to ask how to do that it's probably best taken to someone else to fix.