trimming the valve Stems - just when I thought things were going well

[kiwiz]

I put my head on without major drama and even the cam timing was a pleasure but that soured today as I discoverd the valve clearances were not correct. All the inlet were in the range of 0.05mm to 0.10mm which I thought were okay but all the exhaust were so tight I couldn't get the 0.05 mm feeler in, although unloaded the shim carriers can be rotated which suggest clearance >0

What really got me was that both 1 and 2 exhaust had shim thicknesses of 2.00mm and 2.05mm, with the 2.00mm I understand the thinnest shim you can get?

looks like the valve stem tops need a haircut.

Has anyone ever done that and is about 0.20mm (say 10 thou) about the max that can be wipped off? Sort of thing for a wet night in the garage with the disc grinder? Is there any other way such as new valves or has the meat come off the seat rather than the valve face?

[Garn 1]

KiwiZ, I know the drama you are going through. Usually this is caused by re-seating & re-facing the valves too deeply, so the stem protrudes too much.

The answer is to "tip" the valves, as you mentioned. This is simply facing the ends of the valve, however. 2 mm does seem a little too much, as it said that the tip would be softer the further down the stem you grind. I have seen the case where an engineering judgement was made and the valve collets were ground down about 1 mm to allow tip to protrude enough.

I think I would test the whole set-up again using a new valve as a test piece.
There is always an advantage in doing a preliminary check of shim size with cams-shaft in place and with head supported on bench. I expect these were not new valves.
Good luck & regardZ

[Hack]

Not sure about a "J" but the original Kawasaki manual for the Z1 - Z900A4 says when you run out of clearance on the thinnest shim you can grind the valve stem so long as you leave at least 4.1mm above the groove. Haven't got a valve to hand so not sure how much meat there is above the groove to start with.

Hack

[Rich]

Minimun after grinding is 4.2mm from the top of the collet groove, which is a grind of 0.3mm on unaltered stems - Kawa manual.
If you do have it done it needs to be square to the stem or the bucket will slap in the head as the valve turns and you will get a ticking noise which comes and goes, the valve clearance will also alter as the valve moves round and you'll end up pulling the head again. Get someone who knows what they're doing to do them and speaking from experience I'd put two new valves in if it is due to having the heads of them faced.
Have you put new guides in? If so try swapping the valves over to see if you can get the clearances with a slight lap in.

[kiwiz]

Great feedback as usual guys.

As far as I can remember the workhop cut one of the exhaust seats but two seem really tight. Valve guides were not replaced as they all seemed fine.

I think I will get the stem tops cut the 0.2mm provided the 4.2mm length between top and collet groove is maintained. It's a b*gger having to take the head of again and the two celebratory ales were a little premature, but thats life!

I am not sure that a new valve would solve the problem. Admittedly this is probably not the first time they have been lapped, but I suspect what has come off the faces would be minute in that process.

Is there any way to tell if they have been refaced by looking at them. If so it might warrant two new valves

Garn, I was interested in your comments about doing this on the bench first because this was a question I asked on a thread some time ago and got the feedback that this wasn't desirable. It seemed sensible to me to do it on the bench to get a macro set up and then do a final check again on assembly. However if setting it up on the bench first how do you rotate the cam with the risk of accident damage- those springs have some pressure?

[Rich]

To get the valve height and shim size you only have to measure the height of the valve stem to the cylinder head, this can be done without anything in the head apart from the valve and guide that is. APE do a stop and go tool especially designed to tell you if the height will be within the desired range, but a good vernier will do the same.

If the head has been refaced on the valve you should be able to see it compared to a std one. Did you have the valves refaced as well as the seat recut?

[Garn 1]

That bench check (I've done a few, however, it was about 3 years ago).

Firstly I check that the cams are free to turn without any valves or springs in! There freedome is hard to check whilst loaded with springs.

Next, I assemble the valve in the guide with the bucket in place, with finger pressure holding the valve in place (no springs). Put the smallest shim on and see or measure the clearance to the cam-shaft tip, with feelers. Do one at a time and the approx shim may be calculated and noted.

Assemble the valves with springs and the clearance shim in place. Err to the max clearance, to avoid nil clearance. As previously mentioned, swap valves to obtain the best configuration. This may entail a final lap before final assy of head.

RegardZ

[DogsbolloxofZ1B]

Personally I would ensure the centre-line of the cam is correct first! i.e. The shell bearings are correct thickness so the cam isn't sitting too low. Once satisfied (assuming throw of cam is std) then as everyone has stated, just ensure the collet & washer cannot come into contact with the underside of the bucket.

Good luck.

[Rich]

Good job I bought this manual cheap!!

Installed valve Height.
That is the distance from the top of the valve stem to the cylinder head You have to remove the bottom spring seat as it needs to be to the alloy of the head by the valve guide

Less than 37.19mm = valve stem excessively ground or previously ground. swap and recheck

37.2 to 38.0mm = normal / acceptable

38.01 to 38.30 = wear of valve face / face or seat gringing have dropped the valve excessively in the head - Move valve to shallower cut seat, remeasure or gring 0.3mm max off stem.

More than 38.3mm = scrap

[kiwiz]

guys,
thanks again for the feedback. These sessions are great for reminding me that I am a banker not an engineer. Frankly without your comments Garn, I still would be wondering how to rotate the cams on the bench with the springs in place. Take the springs out! Great piece of lateral thought.

I took the head with valves to the shop yesterday. Explained to the tech what was required: 0.2mm off subject to mimimum collet groove to top distance of 4.2mm. By the time I finished explaining how important it was that the tappet dimple not push on the collets I think he was about to throw me out. Should be back in a couple of days.

I agree the correct process would be to measure the tip to head length but I understand this involves removing the bottom valve spring seat which in turn involves removing the guide seals. Given my previous experiences with this (see earlier thread) when I destroyed all of the old getting them off and two of the new ones putting them on, I really don't want to go there again.

As the clearance was >0 as fitted with the smallest shim and assuming the stem haircut is within the tolerances allowed this should allow the replacement shim to move up into the 2.1mm range with enough clearance.

Now as all my replacement shims are around 2.5mm it looks as though I will have to avail myself of the club exchange services. One bright spot in all this is I still have from the 70's the special tool to hold down the tappets.