Clearances

[Richard Q]

After discovering that the inlet valves had been filed down, perhaps to obtain sufficient valve clearances, I bought some new ones and fitted them. The old ones were actually slightly below the spring retainer, so not clever

Now I have some negative clearances, i.e. the valve is still open with the cam pointing away from the tappet.

So, I am going to need some thinner shims, but because it is very difficult to measure the amount the valve is open, I may need a couple of goes at it

So, the valves are here at the moment

1= 12 thou open, 245 thou shim

2= 10 thou open, 270 thou shim

3= 12 thou open, 240 thou shim

4= 10 thou open, 245 thou shim

Now I suppose I need (for 1) 245 - 12 and minus the gap I need - say 4 = 229.

Does this sound about right? is there some sort of shim exchange scheme?

Any help would be appreciated

Richard

[KeithZ1R]

the shims are metric ....just sayin

[Richard Q]

the shims are metric ....just sayin

oh dear

OK - the gap under the valves is still 10 thou, and the clearance needs to be 2 to 4 thou? is this correct?

Cheers for that

[jimmock]

Sounds like you have receding valve seats.

[KeithZ1R]

Sounds like you have receding valve seats.

summat aint right. Rob will be along at some point to steer you in the right direction

[Richard Q]

Sounds like you have receding valve seats.

I thought that too, what are the thinnest shims? Looks like I need something around 2.00. Or I need to replace the seats - can that be done on the Z900 head?

Richard

[ruffle]

It is legit to 'tip' the valves (take some off the camshaft end) thereby shortening them and getting back within the normal range.

The workshop manual tells you how much is permitted (must have at least 4.1mm above top of collet groove on a Z1; others might vary).

[edit: FYI - Just noticed the Uni-trak manual says not to tip the valves).

[Richard Q]

Cheers Ruffle, but there's tipping and hacksawing the end off

I have done a small calculation and found that if I can get a 2.05, 2.35. 2.00 and 2.10, I can get two clearances of 3.75 thou, and two of 3.78 thou. Although that's depending on how well the valve opening has been measured.

Is there a club exchange scheme? I am a member

[ruffle]

Yes there is.

Contact Jerry for the large (overbucket) ones and GB for the 13mm (underbucket) as detailed in the sticky at the top of this forum.

[freddyz1r]

Is there a club exchange scheme? I am a member

yes richard, contact Ginger Bear, I think he is the holder/distributor of shims.
cheerz freddy

[PAULJAC47]

I had a B with just the same prob as this,tried tipping the valve tips and trying to get some small shims(dont be tempted to have em ground down) but in the end had some new seats fitted,trouble is if you are keeping the bike its hard to get shims smaller than 2.0 rule of thumb by the by, is 5 on the shim=2 thou
so a 240 shim is 2 thou thinner than a 254...Paul J

[zed1015]

the shims are metric ....just sayin

oh dear

OK - the gap under the valves is still 10 thou, and the clearance needs to be 2 to 4 thou? is this correct?

Cheers for that

You need to start by taking those clearance measurements in metric .
Take them on the base circle with the lobe pointing directly (180 deg) away from the shim
You want between 0.10mm and 0.15mm clearances, preferably the higher figure.
Going as wide as 0.20 with performance cams.
If you need to go in to the low 200's (200 - 220) shim range then you need take some off the valve stem while it's apart now and get them in the 250 range.
200 is the thinnest shim and if built with that you will be stripping the head off again very soon to do the above work as the gaps will close as the new valves etc settle in.
With unmodified collets and retainers you can take 0.30mm off the stem tip and if you have access to a lathe some more can be had by trimming the collets and retainers.

[KeithZ1R]

Told you

[jimmock]

Told you

You did !!!

[Richard Q]

Told you

You did !!!

Indeed he did

anyhoo - so No. 1, from 245 to 205 gives me an extra 0.4mm of clearance, which multiplied by 39.37 to give me thou = 15.748 thou. Less the 12 its already open, leaves 3.748 thou clearance.

Correct?

Richard