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.


--
BMW K1100LT Ducati 750SS Yamaha XTZ660 Tenere Honda CB400F CB250N SH50
chateau dot murray at idnet dot com
"What you're proposing to do will involve a lot of time
and hassle for no tangible benefit."

 

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.

 e:


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? :-)