Tipping/Shortening Valves - Shortening collets and trimming retainers

[DeadZedDave]

i've read Kawasaki manuals recommendation to shorten valve stems up to 0.3mm to regain clearance. I've also read others say UP TO 1.0mm can be safely removed. Also I've read that valve collets can be shortened at the TOP and valve retainers trimmed /thinned down, the collet and retainer modifications being to ensure that the underside bucket stays clear.
Can anyone please confirm:
Max. Valve Stem Shortening Length ?
Maximum Collet Shortening Length ?
Maximum Retainer Shortening Length ?
So much has been written over the years in so many places.
It would be good to have an up to date perspective / set of measurements
Thanks in advance !

[zed1015]

Shim on top collets and retainers can be skimmed/shortened by 1mm and combined with further valve stem tipping will get you back to max shim sizes once you run out of clearances when going by the book.
They may tolerate more but that's as far as i and others have gone without failure.
Stems can be trimmed by much more to maintain the 37mm valve stem height if you are sinking valves etc .
Stock Kawasaki says a max 0.3mm for tipping the valves but this is with stock untouched retainers.

[Mathh]

@Zed1015... I always heard that 0.3mm was max because of surface hardening of the valves. Does this mean that the valves don't have surface hardening?

[zed1015]

Tipping by 0.3mm max is only to ensure that sufficient clearance remains to prevent the underside of the bucket riding on the top of the stock retainer and not because of any hardening of the stem tips.
I've been running 1.3mm tipped valves in my Z1R for 25 years with no mushrooming of the stems.

[DeadZedDave]

Thanks zed1015. I know I've read the information before, a while ago but trying to find it again proved impossible.
I'm wondering if the moderators might make this one a "sticky" ?
HOWEVER, a further related question:
How much should the valve stem protrude above the collets - I'm looking at a Minimum size ?
The reason I'm asking is having found some previous work done by someone else, I'm trying to decide if it can be tidied up or if I need to re-do it with replacement parts. It looks a mess but apparently it ran like it is - at least for a while. Distance / height from stem tip to top of collet is minimal ! I'm aware that the bucket has a raised pip in the middle underneath which bears on the top of the stem, but any thought on a minimum dimension to work with would be welcome. N.B. I'm looking at something somebody did 30 odd years ago - so no which hunt !
Any input appreciated !
My memory's bot what it used to be....

[zed1015]

On average stock tip height above the collet is 0.8mm.
After factory recommended tipping of 0.3mm this is reduced to 0.5mm so be looking at that as your minimum figure although this is Kawasaki playing it safe and you can get away with less.

[DeadZedDave]

Great ! Thanks again zed1015. I've got 0.5mm clear. I might even overlook the way it looks - its not as though anyone will see it - not until after I'm gone anyway......
Your help and knowledge is much appreciated !