Challenging a common belief...

[XSokieSPECIAL]

Thanx Tod,

Some of you may or may not remember my thread a couple of months ago " noisy valves". I raised this very same question.

In my expierience in the automotive repair field valve adjustments tend to loosen over a period of use due to cam wear, lifter wear,push rod wear, rocker arm wear, and valve stem (tops) wear. However, in engines with the overhead cam systems like are on these engines, there is virtually no need to adjust them. Unless there is an oiling problem and/or some component is replaced. It is a nearly perfect system in my opinion.

When I discovered ,finally, that my noise was due to loose cam bearing caps and did go ahead and adjust the valves, I found 2 were slightly loose and 1 slightly tight.

I still need a lot more experience with this engine but I still tend to lean toward loosening the over time theory.

Just my 2 cents.
Greg

[DiverRay]

Back when I worked at a Fiat dealer I measured the shims taken out after valve adjustments. If the measured thickness was different than marked (or someone put it in upside-down and wore the markings off) I would re-mark them. Sometimes they needed re-marking but usually not.
I would swap shims with customers doing it themselves at no cost. They had enough other problems

Pat, I worked as a parts guy in a Fiat Dealership!! My big thing was the stock brake rotors!! We sold them over the counter for $11.35 Each, BRAND NEW!! The X19 was a real POS, but the 124 Spyder was a great car, IMHO. The dual cam 1.8 liter engine would last longer than the five speed transmission!
Back to the thread:
I have had to put SMALLER shims in almost every engine I've worked on. This is my running three, and about three other bikes in the past year alone. My first bike, from new, only needed smaller shims as well.

[Ivan]

I wonder if the apparent loosening isn't coming from the cam caps wearing?

[aussixs11G]

abbreviations...

what does 'IMO' and 'IMHO' stand for??
Bryan

[b.walker5]

what does 'IMO' and 'IMHO' stand for??
Bryan

In My Opinion and In My Humble Opinion

[jmnjrpa]

If you are experiencing wear at the cam/caps/bearings that engine will be very noisy and in need of intensive care VERY shortly.

[Ivan]

what does 'IMO' and 'IMHO' stand for??
Bryan

IMO = In my opinion
IMHO = In my (more than likely not very) humble opinion
IMHBVAO = In my humble but very accurate opinion.

[trbig]

Posted in wrong thread.. Disregard..

[Trainzz]

My 2 cents

like anyone here has humble opinions............sheesh!!!!

[Ivan]

If you are experiencing wear at the cam/caps/bearings that engine will be very noisy and in need of intensive care VERY shortly.

I was thinking just a few thousandths worth of wear, changing the valve lash, not like a a whole bunch...

[Geezer]

I was thinking just a few thousandths worth of wear, changing the valve lash, not like a a whole bunch...

Once you get through the surface hardening, the wear like crazy...

Geezer

[b.walker5]

Heres what they look like after the hardening is gone. It a poxy little Opel engine that was in my daughers last car. Apart from being a little hard to start, it ran fine and she sold it that way to an unsuspecting buyer..

[jmnjrpa]

That's bad, Brian. I am glad you kept the picture.

About the cams, they are flame hardened, not a true case hardening. Flame hardening crystallizes the surface to a few thousands depth whereas case hardening actually adds carbon to the iron to the depth of .02/.06 average. Case hardening is not quite as hard but lasts far longer and increases the size minutely. Some steels such as the valve steel are "core hardened" but that is too problematic for items such as cams.

[Ivan]

Once you get through the surface hardening, the wear like crazy...

Geezer

No, no the cam caps, not the cams. The caps on the XS are aluminum, which AFAIK can't be surface hardened. Maybe anodized, but that wouldn't work well in this application. The valve springs push the cams into the caps, causing them to wear, and the lash gets bigger. I have heard of others saying they had to mill a bit off the lands of the caps to get the clearance back into spec. FWIW, aluminum has the wear characteristics of uncured jello, so it would make sense that the caps would wear long before the bearing surface of the cam. And much longer before the lobes.

[jmnjrpa]

The caps can be hard chrome plated along with a few other methods. A flash of hard chrome would last virtually forever. Problem is, they would have to match within tenths (minus oil clearance) to the cam journals. Very slight mismatch and you have 72+ hardness (C scale) against your cams at 62+. End result is the caps would eat your cam up. That is over simplified. If you plated good caps (.0001/.0002 thick ) with hard chrome and went back on the same engine, it would work.