Pssst. Don't tell anyone I asked, coz I feel like should know already!!

[nurse]

With all the talk of the valve shim kits, I feel I should come clean and ask!  Why would I need to shim my valves, what's wrong with the ones I have?  Is it an age/mileage related thing?

Don't tell anyone I'm asking as with all the chatter about shim kits and everyone so keen to get on board I feel like I should know already!
If anyone found out I didn't know I would probably feel like a right dickhead! So let's keep it in the down low - just between ourselves!

[NJona86FJ]

whispering... your shims are small metal discs of a set thickness , running under your cam lobe governing how far? your valves will open.... as they have the cam lobe running onto them they will reduce in thickness(over time)  not allowing your valves to open as far ( age, lack of oil, general wear and tear) thus reducing engine performance as you can imagine and if left unattended detrimental to you and your bikes health.. ( you pull hair out and the bike doesn't run properly or possibly can have a flow on effect and start to break things...) other bikes run an adjustment system  of lock nut and threaded rod running through a cam follower onto the heads of your valves...(kawasaki).... meaning ( from memory) that you have to at least check them every 6 thousand k's... from my experience the inner  inlet valves used to tighten up sometimes  quiet a lot!! ( trying to remember how much but cant.... sure one tightened up once to about 8 thou....).... fj's dont have this just the shim(disc) that wears a lot slower and doesn't need adjusting  as frequently if as much at all...( reminds me i have 106 thousand k's since i checked mine and should get of my arse and do it....) there is a formula in the fj manual that tells you how to measure and set it up to work out what shim (disc) thickness you will need and how worn your shims(discs) are .
ok found my manual... sorry for the wait!!

[NJona86FJ]

Inlet clerances...0.11 to 0.15 so split the difference = 0.13mm
ex clearances... 0.16 to 0.20  so split the difference 0.18mm
Examples                                                               intake                  exhaust
actual measured clearance ( feeler gauges)                  0.50mm                      0.41mm

subtract specified clearance                                      - 0.13mm                     -0.18mm
equals excess clearance                                             0.37mm                      0.23mm

Existing pad number                                                     220                            245
add excess clearance number                                        + 37                           +23
Equals new pad number                                                257                            268
round off to nearest number                                          255                            270

Ok the pads are shims (discs) they are stamped with numbers , but ALWAYS  measure with micrometers  and double double double check. and check again.
hope this helps , if anyone see's anything wrong please correct me but to the best of my knowledge  ( and manual) thats what shims are. not ladyboys.
im assuming the shim kits would be handy as you wouldnt have to order and wait for then you already got a selection.... the numbers quoted above are only examples ( except the specified clearance)

neil

[nurse]

Well how's about that, now I know.  Knowledge truly is power!

Now I understand, I shall extrapolate from my new understanding that as the bike has only done 4500miles since it left the factory, that I am unlikely to need to worry about this issue!?!?

[NJona86FJ]

take your rocker cover off and get some feeler gauges and check    cant hurt, you cant break anything  and its good practice... cos feeler gauges rely on "feel" and everyones "Feel " is different.... im usually 0.01 mm out using micrometers cos im a bit heavy handed

[Steve_in_Florida]

With all the talk of the valve shim kits, I feel I should come clean and ask!  Why would I need to shim my valves, what's wrong with the ones I have?  Is it an age/mileage related thing?

This is actually a very good question, as not everyone has any idea just *WHY* checking your "valve lash" is important.

Air cooled engines are designed to very close tolerances, and the dissipation of heat is paramount to the longevity of the engine parts.

The combustion chamber develops extremely high temperatures, and that heat has to go somewhere. (Remember, there are EXPLOSIONS happening many thousands of times each minute, just inches from your kneecaps.)

At the point in the combustion cycle known as "top dead center", both of the intake and exhaust cam lobes are facing away from the tip of the valve stem, and the valve should be fully closed, effectively sealing the combustion chamber. When the mixture of fuel and air is ignited, the explosion should ONLY drive the piston downward.

During this time, the valve's sealing "faces" are firmly seated against the head, allowing excess heat in the valve itself to dissipate.

The distance between the cam lobe and the tip of the valve stem is regulated by the use of "shims". If too thick of a shim is installed, then the valve will be partially open in the combustion chamber, and the valve will begin to burn. If too thin a shim is installed, then the valve will not open enough, and performance will suffer.

If the clearance between the valve stem and the cam lobe is too tight, then the sealing face of the valve will *NOT* be firmly seated against the head, and the small opening will allow some of the explosion in the cylinder to escape underneath it. This results in a valve that cannot get rid of its excess heat, and eventually "burns". The valve will develop cracks or erosion of the sealing face, which further magnify the problem.

Once the burning process starts on a valve, it only gets worse, as the explosive forces of combustion act as little blowtorches on the affected area of the valve.

Here are some examples, pulled from the web:
(Note, generic pictures of BURNED VALVES, not specific to FJ motorcycles)







Hopefully, these pictures will frighten you into checking your valve clearances on a regular basis, and help you to understand why routine maintenance is important.

Steve

[NJona86FJ]

   thats awesome steve....

[Arnie]

Neil said, "your shims are small metal discs of a set thickness , running under your cam lobe governing how far? your valves will open.... as they have the cam lobe running onto them they will reduce in thickness(over time)  not allowing your valves to open as far"

Actually, the shims are very hard and will wear only very, very slowly.  What changes most in these engines is the valve seat which will get pounded thinner as the valve face hammers into it with each revolution.  This eventually will take up all the free play (lash) in the setup and you'll start to burn the valve face (as has already been explained).

Arnie

[nurse]

Wow, thats certainly an explanation!  Thank you for that!  

So are you (thats the royal you as in everyone) saying that mileage is never a factor, even if the motor which has only just run in, is no reason not to check!  Surely the shims and/or seats won't need attention after only 4.5k miles?!

Surely that would be in the service book check list! I have the original one for this bike and there is no mention that i can see.

[Steve_in_Florida]

So are you (thats the royal you as in everyone) saying that mileage is never a factor, even if the motor which has only just run in, is no reason not to check!  Surely the shims won't need doing after only 4.5k miles?!

Surely that would be in the service book check list! I have the original one for this bike and there is no mention that i can see.

Well, if you're confident that some schlub at the factory did his job right and set things correctly, then you probably have nothing to worry about for a while.

Personally, I like to have PROOF that clearances are correct.

C'mon, didn't those pictures scare you JUST A LITTLE??? Makes me want to run out and check my valve lash ***RIGHT NOW***!!!

By the way: YAY RANDY (RPM) for spearheading the club shim kit idea. What a guy! Now we have NO EXCUSE for ignoring our valve lash.

Steve

[Arnie]

Yamaha Service Manual calls for check at 1000 miles and then each 8K miles thereafter. 
This is a fairly early version of the service manual and I'm pretty sure they pushed the interval out to 12K miles in later printings.
You'll find that the greatest change in lash will usually be early in the engine's life.  After a while it all settles down and at most checks you will only have one or two shims that need changing.
However, checking is pretty easy and doesn't cost anything to do except a bit of time.  Wouldn't you like to KNOW they're in spec?

Arnie

[nurse]

Well if I said there was no seed of doubt now germinating I would be lying, but by the same token I don't think the kit was gonna be an international affair (we have laws against that kind of discrimination this side of the pond! ) so I am at a significant disadvantage when it comes to doing the job in the first place!

[Arnie]

Checking only requires a set of feeler gauges, after you've removed the valve/cam cover.
Shims and shim removal tool is only needed if the lash is wrong and you need to change a shim.

Arnie

[Dads_FJ]

Well if I said there was no seed of doubt now germinating I would be lying, but by the same token I don't think the kit was gonna be an international affair (we have laws against that kind of discrimination this side of the pond! ) so I am at a significant disadvantage when it comes to doing the job in the first place!

Perhaps there's a shim kit available here. http://www.fjfjrbiker.co.uk/fj_forum/index.php.

[markmartin]

I was directed to this write up when I did mine.  http://www.xjrog.co.uk/smf/index.php?topic=666.15