Swapping cyl.head and not the cams...

This is on a 1980 CB750 DOHC...
I had an upper timing chain break, resulting in 2 bent valves and worse, 2
broken valve guides.
Rather than trying to swap valve guides, I picked up a cylinder head from
the same year model really cheap. It has the cam bearing caps, but not the
cams or the shim buckets.
So my question...
How bad is it to use the old cam and shim buckets in a different head?
Must this be machined to match? Should I plastigauge it?

 

You'll be fine. It's the cam bearings that are matched to the head.
Otherwise, if you think about it, you'd never be able to replace a
camshaft without changing the head as well, which would have put
Yoshimura and others out of business decades ago.

 

Plastiguage is a crushable plastic fiber which is typically used to
approximate how much clearance there is between the crankshaft and the
main and rod bearings.

Plastiguage is an inexpensive substitute for precision micrometers.
The home mechanic can determine whether he needs over-sized bearing
inserts or if the crankshaft is badly worn without buying the expen
$ive
micrometers.

As I recall, the original Kawasaki Z-1 engine had removable cam
bearing inserts.

However, modern Japanese overhead cam engines don't have bearing
inserts
in the head, they run the camshaft directly in the aluminum head and
if the
head is damaged you would have to replace it, unless you can find a
really good motorcycle machine shop that knows how to line bore the
bearing caps and head.

In any case, you need the factory shop manual to find out what the
dimensions of the cam bearings and lobes should be and then you need
to use a bit of judgement if the parts are worn a thousandth of an
inch or some more than the manual limit.

 

<snip>


In other words, you have not answered the question. So you don't
actually know what you are talking about. On a great many Jap bikes,
the cam caps are matched to the head, like I said.

Oh, and some modern Japanese bikes use roller bearings in their heads
as well.

If the head and cam bearing caps are in fine condition, and ditto the
replacement cams, then all the OP needs to do is to bolt in the
replacement cams and ride away.

If any or all of the cam caps and head bearings surfaces are buggered,
then obviously he'd need to do a whole load of work, but the fact that
he's trying simply to avoid replacing two valve guides (not in itself
a tough job, but one for a specialist) would suggest that there's
nothing wrong with the used head he's bought. And if the camshafts he
wants to put in it were buggered also, I don't think he'd be shoving
them back in his bike.

Barrett - like I said, just put the cams into the used head, and bolt
that onto the block.

 

First generation Honda pile-of-craps had roller bearings on the ends
of the cams.

But name just *one* Japanese design from the middle 1970's and up that
has *roller bearings* in the head.

If you can be bothered to support your incessant *quibbling*, that is.

 

Kawasaki ZX7R. Kawasaki ZX9R. Both do, at the camchain drive end.
Possibly others as well, and I cba to check right now, but those two
do for certain, and I know, because I've worked on 'em. Which,
evidently, is more than you have.

Plain bearings elsewhere, but nonetheless roller bearings they use.

Are we feeling stupid now?

 

That sounds about right - when I blew up my first CB900 (long stroke
version of the same engine) we used the inlet camshaft & buckets from
one engine & exhaust cam from another.

It went fine until it suffered an ignition failure and I replaced it
with a cheap VFR...

 

Oh, and as you're so fond of posting fiches, here you go:

http://tinyurl.com/6dvryp

You can clearly see the ball races at the end, by the cam sprockets.

 

Whatever got you so worked up that you actually looked something up to
win
a useless argument?

What does this have to do with a 1980 CB750, anyway?

 

Bwaaahahahahaha! Look at the timing of the postings. I'd already told
you the truth, before I even bothered to look this up.

In other words, I didn't look it up because I needed to "win an
argument". I already knew it. I gave you the link for your benefit,
because I'm a nice chap.

And why did I state it? Because you, *once again*, paraded your complete
lack of knowledge in a technical ng and your ignorance warranted
correction.

Bwaaaahahahahaha! You utter, utter *loser*. You give the OP a load of
irrelevant waffle, it's corrected for what it is, you start jumping up
and down and screaming, demand proof of what I said, and it's
provided...

....and then you ask a question like this?

LOSER!

 

If we include all bearings containing rolling components, SR500 and
(probably) derivatives had a camshaft supported in ballraces. Or are
we restricting this to rollers?

 

*Who cares*? What will be gained by playing The Old Gasbag's game?

The original poster had a question about a 1980 CB750 DOHC, but the
Old Gasbag just had to trash the thread with exceptions and ridiculous
argument.

Like he always does...

 

Well, I was taking ball races to mean 'rollers' in this conext, as
opposed to plain bearings, and having owned an SR500 I know what you say
is true. And the XS650 used them as well, but Krusty *did* say "just
*one* Japanese design from the middle 1970's and up", so I deliberately
didn't name them.

 

You do, remember? You got all shouty and issued a challenge and...

It was taken up.

And now you're getting even more petulant because you've been made to
look an idiot. Which, it has to be said, happens frequently.

I mean: "Lighter vehicles are sprung more rigidly than touring sedans".
What a load of bollocks.

He did. Which I answered succinctly and correctly, and which you didn't.

What's your next point?

 

My point is that you were an exceptional child, bored with your school
work and always seeking alternative amusement or demanding attention
from the beleaguered teacher.

Nowadays that would be called "attention deficit disorder", or ADD.

And you grew up to be an exceptional adult, a pain-in-the-ass who is
always looking for a tedious exception to every generality just to
draw attention to himself.

Adult Attention Deficit Disorder...

I suppose we will now see this thread mushroom out to fifty or a
hundred
useless messages, instead of dying from disinterest.

Why couldn't you just have a passion for philately combined with Zen?

You needn't answer that rhetorical question.

 

<Snip>

Troo.....

Do you see what a complete arse you are making of yourself? Obviously
not, so:

1. OP asked a decent tech question.

2. I provided a decent tech answer, which was entirely correct and was
later substantiated by another poster, from personal experience.

3. You posted reams of irrelevant waffle and didn't answer the
question at all.

4. I pointed out the irrelevance of your reply, added a very brief
throwaway line about camshafts, and reiterated my advice to the OP.

5. You jumped down my throat, wittering on about 1960s Hondas, and
demanding evidence of a 'modern bike' using the sort of cam bearings I
carelessly mentioned.

6. Said evidence was provided.

7. To try and cover your imbecility and ignorance, you then started
squealing that this was irrelevant to the OP's bike, conveniently
ignoring the fact that (a) you had issued the challenge in the first
place and (b) that the OP's bike question had been settled right at
the start of the thread.

8. And now you accuse me again of causing the thread to divert from
the OP's question. See (7) above.

You are a sad, sad, frustrated, hate-filled, warped, perverted,
ignorant, stupid little waste of spermatazoa. Sorry, but it has to be
said

 

Oh, and while the king was looking down,
The jester stole his thorny crown.
The courtroom was adjourned;
No verdict was returned.
And while Lennon read a book on Marx,
The quartet practiced in the park,
And we sang dirges in the dark
The day the music died.

99.9999999% of all spermatzoons fail to perform their task, but the
world was cursed with The Old Gasbag.

Take your soap box to Speakers Corner and rave at the crowd.

 

<snip>

And again, the last resort: childish insults. You really need a better
scriptwriter <G>.

 

Ah. In retrospect, I replied to the wrong person. It made sense at the
time, honest.

 

Next time you see TOG humping somebody's leg, just remember what
Randy Quaid told Chevy Chase.

"It's best to just let him finish what he's doing."