How to determine shim sizes after valve/seat grinding?

Hi everybody,

First I'd like to just mention that although the bike is an FJ, it has the same engine as the XJ, so please forgive my boldness in posting here, but in the past you guys helped me out quite a bit with advice.

The subject pretty much says it all. I had been working on rebuilding a spare head for my bike, and part of the job was that I grinded the seats and valves. Upon installation I noticed that there is no clearance between the old shims and the cam.

I just don't have so many shims to try different sizes until the correct one fits. How would I determine, approximately at least, what shim sizes I need?

Thanks in advance for any inputs.

 

Sorry I don't have much good news on this one.

Get yourself (at least) one really small shim - one you're positive is going to be too small for the engine. Have to do each one individually -- take out the shim that's there, put in the small one, measure the clearance - and from that you can calculate the size you need to be in spec. Take small one out, put original back in, and move to next valve.

 

Not sure what kind of equipment you're working with, but I'll tell you what I do when I rebuild a head with solid shim on bucket setups. After the valve job, but before final assembly, I install the buckets, shims, cams, and caps, and then slide the valves in (with no springs, retainers, etc.). Then, press the valve up by hand and grind the stem until you get the desired clearance. This will only work if you have a precision valve grinder to ensure that the valve tip is ground 90 degrees to the shaft. That's the way I've done heads for years, haven't had a problem yet.

 

I don't have a precision valve grinder. This being the first head I rebuild, I didn't foresee this problem, though it's very obvious. Next time I'll do it different. It would be too much now to pull out the head again.

I was thinking of the following method: to take out the shims, and position the cam right, then to insert some modeling clay in between the bucket and cam. Then take out the modelling clay which has been flattened to the distance between the bucket and shim, and measure that. I know it's not precise, but it may give me a rough idea about the shim size needed. Any thoughts?

 

Sounds like a good idea to me. You will still have to get a slightly smaller shim as Altus pointed out but the clay should get you a ballpark figure on where to start at. Remember to buy smaller than what you measure in the clay, you can always adjust with larger feeler gauge blades.

 

I had the same problem on my Maxim X. The previous owner let the valve job go so far that there was no clearance left.

I have heard that clay is not a good idea because it has some rebound to it after it is flattened. In other words, it is not accurate at all.

What I did was take my old shims out and grind them down the amount that the clearance was supossed to be. In other words, I was supossed to have 8 thousandths on the intake (I think). So, I took the shims out and ground them down.

Then, I put the shims back in, and started the bike, because I thought the clearances might change slightly after it would run for a while.

Then, I measured the valve clearances. Then, I took the shims back out and measured them with a micrometer. I then calculated the new shim size, and ordered them. I then waited two months. :roll:

Then, I installed them, and it worked! (There are a few details I am leaving out, but it sounds like you know what you are doing)

One thing about this method - don't run the bike for long with ground shims in. Grinding removes the hardened layer, so you will get premature wear on whatever the shim is hitting.

Also - if the shim is what is making contact with the cam, grind the side that makes contact with the lifter. If you ground the cam side, it would wear very fast since the cam wipes the shim.

My shims were under my lifters, so I didn't have that problem.

 

ohmega, I don't have any spec's for the FJ, but if it's the same as an XJ, here's what you should be doing.

Write down the thickness of all the shims in their current position.
Then check your current clearances for each valve and make note of them.
Locate a valve shim clearance chart and it will tell you what shims should be put in each location. A shop manual usually contains these charts.
If you have one or two or more valves currently with no valve clearance, then you could swap in the smallest thickness shim and recheck clearance to use the chart to find the correct shim size.

You don't play with clay or grind valve stems, or need any expensive grinding tools. From what I understand the Maxim X engine has the shims under the bucket so the cam won't contact them, but on the normal 4 valve engine the cam is riding on the shim. On this style of engine I wouldn't use a shim that was "ground" for fear of taking out a cam lobe.

My 2 pennies worth!

 

If you don’t have any clearance at all my suggestion would be to take one that seems to fit better and with out the need of a special tool to grind it down use water sandpaper glued with any spray adhesive so that the surface is homogeneous, to a 6mm glass them when’d you have the necessary clearance in one of the valves just change that shim around all the valve seats calculating what you need for the rest.

 

PS: Don't forget to do this on the bucket side of the shim

 

Like magalo said, if you do it on the bucket side of the shim, and do it carefully, I wouldn't anticipate a problem.

You probably don't have to run the bike with the ground shims in, so that would almost guarantee that you won't have a problem.