TOPIC:

I lapped the valves yesterday on a spare engine I am putting together and made measurements of the valve stem length, stem diameter and inner and outer spring length to ensure they were all within service spec. The head is pretty nice and I used my new expensive lapping tool which has a rod that you push to cause the suction cup to stick. It really did a FANTASTIC job and I will probably have better seal than normal because it was so darned easy to use. I usually get frustrated with a normal lapping tool as they just don't want to stick and end up with a taste of lapping compound... yuch! In any case, when I measured stem length, it occured to me that it SHOULD be possible to predict pretty exactly the shim needed to provide the proper clearance. Anyone have an idea on how it could be done. Max stem height with the valve in the guide is 38.07mm on a KZ900/Z1 style head. All my valve stem height measurements were in the 37mm and change range. Shims run 2.00mm to 3.10mm I believe and in .05mm increments.

I think it would be hard to predict because if the valve seats have been machined and the valve faces have been machined it will change the amount of valve stem that will come through the guide. Even if you messure the amount of stem that comes through the guide there is the question of are ALL of the guides exactly the same distance from the top of the guide to the face of the valve seat.

In conlusion I think it is a good possibility and could be done, but I feel it would be more meassurements and time-consuming than just guessing and trying shims. I'm curious of other people's thought/suggestions.

Mellvis

Mellvis... is that your boys in your avatar pic? bhwhahahahaha Each of the stem heights is a tad different because of valve and seat wear but the length won't change because of guides or the springs or the doohickeys on the bottom, retainers or buckets much... I would expect a shop that does zillions of heads would have considered this so they could accurately preshim after valve jobs... We shall see...

you can buy a specail tool to measure the steam heights, I think if you look at starrett, they have the guage you are looking for.
most of them are made for the automotive market which is too large to fit down into the spring pocket on a bike, I modified one years ago that worked on imports and bikes, if you want I can chase down the tool for you, I still have contacts in the auto machine shop area. I think by now they have one that you can purchase. they are very accurate and you can set the clearences.
I made a cheat sheet and it worked everytime, or you can measure at dissasembly and then reassemble at the same height and it works everytime

Measure the stem height and note the shim needed after installation. Use this information to base off of. If installed height increases subtract that amount from the shim size needed. If it decreases, add that amount to the shim size. When lapping valves with a rubber cup, reach under the head and push up lightly on the valve to get it to spin. If the stem height exceeds the max and your down to the smallest (or close to it) shim, apply the subtraction to the stem height. Or u can just install a small shim and then grind small amounts off of the stem to get your clearance.

Post edited by: nads.com, at: 2005/11/25 18:51

do you know if the 900 and 1000 stem highths are the same.i found in my factory service manual a chart for stem highth and shim thickness.i trying to copy and post.if anyone knows how to please advise how to.would a scanner work or should i use my camera?

nads.com - I know how to use the regular type tool but the one with a mechanical device that pushes the air out of the suction cup works soooo much better it isn't funny.

azchili... I have a KZ1000 service manual as well as a KZ900. Both factory manuals. I will look at the KZ1000 as it is far better than the 900 manual. If memory serves, the 900 manual doesn't even include the stem length spec; I think I got that spec out of the Clymers... Will take a look! thanks. I already KNOW what shims I took out but the problem is, I didn't bother measure to see if they had the proper clearances.

OK... the 903/1015cc bikes are all the same. Longest measured stem length on either is 38.06... if the stem is longer, you need to either grind valve (.3mm max grind) OR new seats are in order. The valve is sitting too deep in the seat. There is a chart in the Kaw KZ1000 factory manual for 77-80 models. This info DOES NOT apply to the 1981 and newer J type engines as they have different valve stem length specs.

There is a chart. I will type up the chart in MSWord and put it in the non-model specific Filebase.