Bucket & Shims

Hi
I wondered if anyone can advise please!
I have had the valves re-seated in my Z13 by a machine shop. The valve clearance tolerances have been reduced drasticaly across the valves from around 4.5 - 5.6 down to around 1.7 - 2.0 All the existing valve shims are way too big and i can't find any shims that go below 2.0. I am assuming this is because anything les than 2.0 may not be strong enough to tolerate the stress incurred under use. I am thinking about having some shims ground down to the required thickness (1.7) has anyone heard of this being done by others and being successful or is this not an action to be considered?
The only other option i was contemplating was to have some material machined off the bucket seat, if thick enough, so as to keep the shims at least up to 2.0?
Any any advise would be very much appreciated, thanks in advance to anyone for any help

Welcome to KZ1300.com

I must admit I have a few concerns about this.

Assuming the correct valves have been used then the valve seats must be much deeper in the head than they should be to make the valve stem protrude that much further up into the head.
It also means the valve springs are not as taught as they should be.
Have you got the head back on the bike or checking valve clearances on the bench with cams fitted?
I would not grind anything off the buckets.
The only way is with thinner shims, but you risk warping or overheating if too thin.

Pete F

Hello Deritrend

2nd what Straight6 says.

Based on such a drastic change in clearance you have 2 choices.

1: If the Head is re-installed, take a chance, grind the butt end of the valve stem, then shim accordingly. Not advisable, just saying what others have done in the past. some with success, others not so successful.

2: The best option for success is removing the cylinder head and making sure the margins of the valves are not too thin, or that the margins on the seat faces are at the correct angles and widths. (in other words, not over-ground) which can be the case, when you see the valve stems riding too high in the head, at the tappets. If you are not sure about this, it is best to sacrifice that new head gasket and make sure.

3: Under the headline of what should have occurred when the vales were ground. With the cylinder head on the bench, the cams should have been installed, after the valve grind, and the valve clearances checked at that time. This way the person who ground those valves can catch any clearances while the head of off the bike.

On another note, It is perfectly acceptable to grind the Butt End to clearance the end of the valve stem. (Provided the valve seats and valve margins are within limits. You will need a Kawasaki Shop Manual to make that determination. It's best to grind the valve stem off of the bike and out of the head. It's the best way to get a squared cut (Grind) off the the Butt End.

If the seats, the valves, or both are too far gone, then you are looking at seat replacement, valve replacement, or both. Seats and valves are still available, but would require professional machine shop services to make sure the job is done right. (Depending on what resources are in your area)

It is ok to replace just a valve or just a seat, if one or the other was ground too thin. Just make sure they are re-ground and lapped in correctly.

If machine services prove too difficult, then you my be looking at purchasing a good Cylinder Head Core off of Ebay. This can be a hit or miss proposition, so have it inspected right after you receive it. This way if it needs to be returned you are not out of your purchase price. Focus on cracks in the combustion chamber and water jackets (Magna-fluxed) and watch out for corroded water passages, plus the notorious bevel gears. Head may need to be decked for gasket seating, but only if it needs it after a straight edge tells you otherwise.

A quality base and head gasket is a must.

Best of luck in getting this resolved, keep us posted.

Todd.

Thank you Todd and Pete for you quick response and very,very helpful advise.

This problem only came to light after i have reached this stage from a complete nut and bolt engine rebuild.

Taking in what both of you have said and analizing which way to go with this, i have thought of another idea i would like put your way which might work and be cheaper if it does.

With the head rebuilt and the cams in place,i started by placing cylinder 1 TDC lined up the "T" on the rotor with the timing mark on the pulsing coil and off i go as per manual. I removed and replaced each shim, one at a time inlet and exhaustt and measured and logged the corrosponding gaps as i went along. Once this was done I consulted the manual for the permitted tolerances for inlet and exhaust valves (from memory)this being 0.05 - 0.15 for inlet & 0.15 - 0.25 for exhaust which equals 0.10 tolerance.

Now, (stay with me), if i have 4 valves at 1.7 and 5 valves at 1.8 could i not reduce my tolerance from 0.10 down to a tighter 0.02, which would bring me up to the minimum acceptable shim thicknes of 2.0?

i.e 2.7 being the initial gap between cam and valve bucket seat, 0.10 being middle of the road tolerance from the manual 0.15-0.25,.........2.7 minus 0.10= 1.7 shim required. Thus 2.7 minus 0.7(3) = 0.20 min permisable shim size!!

I'm sorry it looks complicated but what i'm trying to say is if i reduce my tolerance from 10 down to 7 to bring my shim size up to the minimum 2, what do you think?

Thanks again in anticipation

Tim

I would say this will apply equally well to a z13 as it does to a z9.
When I did a head on a z9 and that would happen unless new valves were used and sometimes even new seats were also needed. If the problem can be fixed with less than 1mm being taken from the measurement of the shims then shim the valve springs to the right tension without coil bind and remove 1mm from the top of the valve stem or less if you only need to do.
Anything more than 1mm to fix and you can probably get away with new valves.
Before you remove the 1mm from the stem use some plasticine and stick it to the top of the keeper and collets then insert the bucket and push it down and twist it till it seats onto the valve stem then remove it and check that there is indeed more than 1mm of room by checking the thickness of the plasticine at its thinnest point on the keeper. More than 1.5mm is desirable but I have run them down to 1.2mm without any explosions.
Make sure you take enough of the stem to allow for changing shim sizes down 2 sizes because you may need to do this over time as wear takes place.

Hello Tim:

Like you state above:

Ideally it is best to be in the middle of the clearance limits for intake and exhaust.



Somewhere near .10 for Inlet and .20 for exhaust. This provides the widest margin for valve train expansion when the engine is at temperature. Too tight a clearance and the valve-open duration time is too much, with insufficient cooling. Too wide a clearance you risk having a shim being spit out of the top half of the tappet, not a good day when that happens.

Not sure if I understand your stated clearance of 1.7 and 1.8. If your clearances are that wide, then this suggests the opposite of my first response. Instead of looking at it from the top of the tappet, use the shim guide tables in the shop manual, they are very accurate in determining shim thickness. All based on tables B2 - B7 and the shim tables, B3 and B4.

A more simple way to explain to the forum would be. (Provide us with the numbers as measured from the bottom of the cam lobe to the top of the shim. knowing those numbers between intake and exhaust will be useful.

Certainly you can swap shims around to obtain the proper clearance.

Another test that should be done is compression and leak-down. Realizing, or assuming you have not started the engine yet you could get some idea (Prior to engine break in) where you stand on compression now. Expecting it to be lower than normal without a broken in motor. This could be one (NON INTRUSIVE) way to inspect those valve margins without lifting the head back off. (Especially the Leak Down Test)

Hopefully my explanation is not too confusing.

Todd.