Calculating shim size after re-seating valves

[zed1015]

I would tip all the valves by the max amount whilst you are in there and get some decent shim sizes in.
This will save a lot of hassle later otherwise you could be pulling the head again sooner than you think.

[1975-S1C]

I think you are right Will. That's what I'll do.
Don't really want to be facing the same issue in a couple of years, as I've no intention of selling.

I'll get all of the stems ground down by 0.3mm and then do a final bench assembly to see what shims I need.

Who do I need to contact for shim swaps when I'm ready please ?

[1975-S1C]

Oops, sorry, I meant zed1015, not Will !

Well anyways, thanks both

[z1bman]

The club offer a 'shim swap scheme' to paid up club members, just contact Jerry

[Big Fluff]

I'd say so, especially as you have the head apart on the bench.
Bung some new Viton stem seals in while you're at it.
Will

[buzzard]

Big fluff, I own a set of valve seat cutters so does that make me an idiot? Buzzard.

[Big Fluff]

Big fluff, I own a set of valve seat cutters so does that make me an idiot? Buzzard.

No Buzz, you're a legend
I'm sure you know where I'm coming from though? The last three cylinder heads I've removed from Zed engines have all had the valve seats ragged and it really f#cks me off

[kev edwards]

We all own big zeds so that does make us idiots of sorts, I have never owned valve seat cutters, so by default that keeps me out of the feckin idiot category.

[buzzard]

Big Fluff, the thing I've seen most is where the seat has been over cut to deep into the head and the seat is too wide. Trouble is when you knock out the old guide then knock in the new ones they can go back in very slightly for want off a better description " on the piss abit" which means the valve is touching one side of the seat but is raised off the seat on the other side. When its like this you have to cut more than you would like to but that's the only way to get a proper seal. Anything with a stem height of 38.00mm or more I grind 0.40mm off the stem length. I try to get shims in the 2.50mm range if possible. The other thing I've seen is loose valve guides in the head, you must remove all the carbon from around the valve guide by blasting otherwise the carbon drags through the head when removing old guide and can wreck the head. Old Z1 heads have the ally bronze guides and these are by now nearly all worn, inlet valve stems all tend to be worn passed the service limits ( 6.90mm) Exhaust valves are nearly all ways pitted. I have got a valve refacing machine but most times it best to fit new valve. Scrimping and saving is a false economy in my book. Oh and I reckon the best valve guide seals are the original Kawasaki ones but they ain't cheap. Buzzard @ the Buzzworkz.

[1975-S1C]

Hey fellas,

This has been rather a steep learning curve for me to say the least, and one that is getting frustrating as progress is slow because of my lack of experience. I had expected (rather naively I suppose with the benefit of hindsight) to take the head off, fix the oil leaks then zip it back up again ! H'mmmm !

Anyways, I need to get the thing back together because as nice as my little S1C is, it's not the same as riding the Zed.

Last night I thought I'd better check the valves and measure them up to make sure they hadn't already been ground down on length before I set about taking any more off. The inlets are all between .06mm and .07mm less than the stock 91.70, but the exhaust ones are a little shorter than the stock 90.30 mm, ranging between 0.11mm and 0.18mm shorter.

I tried to measure the portion at the end of the stems above where the collets sit with a vernier but it's damned near impossible given the chamfers and I'm not really sure which bit of it I should be measuring anyways, I.e. Just the plain shaft bit, or to the end inc the chamfer on each end or what ? Or indeed the 38mm that buzzard mentions (where is that from / to) ?

All in all I'm a little worried / confused that I'm about to do something wrong and end up f'ing it up

If It were possible to take .30mm off the stems as originally planned then that would put me back in a healthy shim size range, but obviously I don't want to overdo it and drop a valve as a result, by taking the stems too short.

Just need to get past this step then hopefully things will be plain sailing to get her back on the road again.

As always your help / guidance is appreciated.
Paul

[zed1015]

With those small discrepancies it sounds like the valves are probably stock and they certainly leave scope for tipping..
You need to measure from the top of the valve stem down to the beginning of the collet groove.
Ignore the chamfer as it's only there to relieve the sharp edge that could tear the stem seal when fitting the valve and to some extent to control mushrooming of the tip which could cause the stem to bind in the guide on removal.
Whatever amount you take off the stem you must leave some stem protruding above the collets for the bucket to sit on otherwise the bucket will ride on the collets and you could drop a valve.
The 38mm being referred to is valve stem height.
This is the length of stem which protrudes out of the head towards the cam with the valve seated and the metal valve spring seat removed.
The spec for this is 37.2mm to 38.2mm from the tip of the valve to the bare alloy bottom of the bucket bore.
Ideally you want to be towards the lower figure to allow thicker shims to be installed but obviously the length of stem above the collets and how much can be removed is the limiting factor.

[1975-S1C]

Thank you sir, I think I understand a little better now.

On measuring, the inlets stems they are all but one in the 37.70's the other being 37.60. The exhaust ones are somewhat longer than that !

If I fit a collet and the collar to each valve and pull it up tight there appears to be about 1 mm of stem protruding for the cap to rest on without touching the collets, so maybe taking 0.3 mm off would be Ok then ?

What does worry me a bit now is that I cleaned up the head and soda blasted but not aqua blasted and looking at the guides that came out they did still have carbon on. I hope I've not dragged carbon through and screwed it all up well I guess what's done is done anyways, nowt I can do about it now I guess ?

Anyways, back to the valves. Seems like taking 0.3mm off should be fine and would deliver me some respectable shim sizes as well as keeping sufficient clearance between the collets and buckets, and the valve length towards the lower end.

[zed1015]

Those 37.70mm measurements should have you currently somewhere around the 250/255 shim range which isn't that bad so taking them to 280 ish by tipping 0.30 is ideal if that is the case.
Be very careful when measuring the heights, a Vernier can give differing results so measure and re-measure .
It's easier to take more off the stem if needed than put it back on.
I've been doing this for years and the Vernier method is tricky especially with the guide in the way, I use a special "Go/No go" height gauge for accurate readings.

[1975-S1C]

You're right there, was tricky with the vernier, but I measured each about 6 times and in different places. It varied a bit but not too much.
The exhaust valves would only need 0.1mm off to get me a 2.5mm shim size so I'll settle for that, it's the inlet's that need slightly heavier surgery. Even so, taking 0.25mm off would get me up to about 2.40mm shim, so perhaps I'll do that. Better to err on the side of caution as you say.

Anyways, thanks for all the help on this, I think I now know what needs to be done to move forward and get the shimming right.

I hope I've not made a schoolboy error with the guides though. Fingers crossed all will be ok, but It's playing on my mind a bit

[1975-S1C]

Here are my calc's which hopefully makes sense / are correct