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!
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!!
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)
:hi:
neil
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!?!?
take your rocker cover off and get some feeler gauges and check :good2: 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
Quote from: nurse on March 24, 2013, 04:34:32 AM
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)
(http://www.smartcarspecialist.com/resources/images/faq/valve-burnt-out.jpg)
(http://i2.photobucket.com/albums/y18/dcast/Misc/burned_valve.jpg)
(http://www.gunnarracing.com/project/966/966-1126-08.jpg)
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
:good2: thats awesome steve....
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
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.
Quote from: nurse on March 24, 2013, 08:12:18 AM
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
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
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! :biggrin:) so I am at a significant disadvantage when it comes to doing the job in the first place!
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
Quote from: nurse on March 24, 2013, 08:26:33 AM
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! :biggrin:) 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. (http://www.fjfjrbiker.co.uk/fj_forum/index.php.)
I was directed to this write up when I did mine. http://www.xjrog.co.uk/smf/index.php?topic=666.15 (http://www.xjrog.co.uk/smf/index.php?topic=666.15)
ONLY EVER CHECK THEN WHEN THE MOTOR IS COLD!!!!! When checking let the motor cool down over at least a 24hr period and don't wipe the oil away in doing that you will get a more accurate reading
Cheers Arnie... :good2: I didn't think of that... valve faces wearing down... :wacko2: i spose i REALLY should open my old girl up and have a look.... she s getting a bit rattly and soft.... oil consumption has gone up a bit too.... :bye2:
25mm shims are used in some models of Yamaha, Honda, and Toyota vehicles. So, if your Yamaha d(st)ealer is unhelpful, try the Honda or Toyota dealer down the road for your replacement shims.
Arnie
I found this somewhere........ all use 25mm shims:
Honda
CB750, CB750C, CB750F, CB750K, CB750SC dohc (79-83)
CB900C, CB900F, CB1000C, CB1100F, CBX (all)
Triumph
Hinckly triples and fours
Speed Triple, Tiger, Daytona, Trophy, Sprint
* All watercooled three and four cyl. models*
Yamaha
SRX250T (87) SRX250TC (87), XT250L & XT250LC Dual (84)
TT350, XT350 (86-00)
XJ600 Seca II (92-98)
XVZ12 XVZ13 Venture Royale Royal Star (83-93) XVZ1200, XVZ12
VMX1200 V-Max (85-02) Vmax, VMX12
FJ1100, FJ1200 (84-93)
Harvy
geez wish i could "find" things like that harvey!!! i had an srx 250... never knew it was shim.....but then again didnt have it long enough to work on it!!! bastard theiving ....... and they set fire to it!!!!
if you need more incentive chech my pics for the fj head, with very bad valves, , never ever ever checked from new, and i was at least the third owner
Really? Only 4500 miles on it? Where on earth did you find such a specimen? My new '92 FJ acquisition has about 8200 miles. I'd bet that it runs like butta... Whether the bike needs shims or not, one thing is for certain, we have many many great miles to be had.
Good luck!
Quote from: Arnie on March 24, 2013, 08:05:03 AM
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
Well chaps, well described by you all but..... :flag_of_truce: two schools of thought here, one that seats compress/wear - closing clearance over time and other shims/cam wears - increasing clearances.
In my experience of OHC engines in general, shims were held under cam followers, hence any wear spread to contact area between cam & follower. In these cases, I was always reshimming to decrease clearances so they were increasing over time. However these were probably poorer quality engineering so cam/follower wear may have been more significant than in an FJ engine.
Checked my clearances today and on all cams -clearances were at maximum allowable. Now I'm aware mine has not been checked for some time and previous owner advised me it was well overdue. SO, if clearances will reduce with seat wear, I'm fine? :unknown: On the other hand if wear will increase them, I need to shim them down :wacko3:
Don't feel inclined to shim them down if seats will wear and close gaps further, my head hurts.....Don't want to stir this but would really like to know which it is, both statements could so easily be correct. Any further thoughts anyone please? :scratch_one-s_head:
Kinda like my comment on chain tightening....loose valves are happy valves (to a point) Yes, you may lose a smige power in that the valves don't open as far (doubtful you would notice on a street bike)..however, Tight valves cause expensive problems.
Wear on the Valve shim from the rotating cam lobe is miminal due to the fact that the round shims rotate in the bucket distributing the cam lobe wear over a large surface of the shim along with being bathed in oil.
Valve seats recede as the miles roll by. Just a fact of life. Valves live in a tough environment.
If your valves are on the loose end of the specification, leave them alone, they *will* tighten up as the seat wears.
Thanks Pat, ok I'll leave well alone, put them down to check again in 5,000 and see if there is any clear effect.
If I am suffering a performance loss? it's the quickest road bike I've ever had (even in my Production racer days), so it can't be much :i_am_so_happy: Just a thought though, no-one has mentioned valve stretch.......but that's another can of worms :bye2:
Well, that's why the shim kit contains an *ASSORTMENT* of shims in different thicknesses, so you can insert the one appropriate to the wear you're experiencing, and still be within the prescribed factory tolerance.
Ask anyone in the Volkswagen (Air-Cooled) community: "Tight Valves become BURNED VALVES"
Too little clearance between the cam and the shim means the the valve is OPEN during the power stroke. Open valves cannot get rid of their excess heat, and become scorched and cracked on the edges. The cracks become fissures, and the fissures become canyons.
Here's a link that's worth 1,000 words:
https://www.google.com/search?q=burned+valve&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a&channel=fflb&um=1&ie=UTF-8&hl=en&tbm=isch&source=og&sa=N&tab=wi&ei=p3NTUe_OIpOw8ATxh4DACw&biw=1440&bih=731&sei=rHNTUaCvGJT69gTO8oCACw (https://www.google.com/search?q=burned+valve&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a&channel=fflb&um=1&ie=UTF-8&hl=en&tbm=isch&source=og&sa=N&tab=wi&ei=p3NTUe_OIpOw8ATxh4DACw&biw=1440&bih=731&sei=rHNTUaCvGJT69gTO8oCACw)
Keep an eye on your valve shim requirements over time. That should answer any question you might have.
Also, you can check the stamped thickness of the old valve shim with a micrometer, and verify whether or not the shim itself is wearing.
(popcorn) (popcorn) (popcorn)
:good2: this is gold. i suppose in overview ... I LEARNT a lot... its a case of which wears first, but please lets not do a hardness comparison test on the materials.... lol... all good info (popcorn)
Is it just me or when you dont play with things mechanical for a while your head goes fuzzy?.... you know brainfade an all that.... must be the blonde
lol
Quote from: Windmill on March 27, 2013, 04:16:15 PM
Well chaps, well described by you all but..... :flag_of_truce: two schools of thought here,
Don't want to stir this but would really like to know which it is, both statements could so easily be correct.
There aren't two schools of thought here. This is not a speculative theory in which there are two camps (like oil, tyres, octane ratings etc). Several thousand FJ owners, some for decades and 100's of 1000's of km's will tell you they tighten up with use for the reasons previously explained. Other engines and other configurations do other things.
Noel
Quote from: Windmill on March 27, 2013, 04:16:15 PM
Quote from: Arnie on March 24, 2013, 08:05:03 AM
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
Well chaps, well described by you all but..... :flag_of_truce: two schools of thought here, one that seats compress/wear - closing clearance over time and other shims/cam wears - increasing clearances.
In my experience of OHC engines in general, shims were held under cam followers, hence any wear spread to contact area between cam & follower. In these cases, I was always reshimming to decrease clearances so they were increasing over time. However these were probably poorer quality engineering so cam/follower wear may have been more significant than in an FJ engine.
Checked my clearances today and on all cams -clearances were at maximum allowable. Now I'm aware mine has not been checked for some time and previous owner advised me it was well overdue. SO, if clearances will reduce with seat wear, I'm fine? :unknown: On the other hand if wear will increase them, I need to shim them down :wacko3:
Don't feel inclined to shim them down if seats will wear and close gaps further, my head hurts.....Don't want to stir this but would really like to know which it is, both statements could so easily be correct. Any further thoughts anyone please? :scratch_one-s_head:
This (http://www.gesslerheadporting.com/gesslerheadporting/ghp.nsf/822dcaaaa26c6da985256dd80023623d/6bf297104a46cb4f85256f96000c1a9b!OpenDocument) is a good explanation of Valve Seat Recession, which is what causes the valve clearances to get tighter over miles....
Remember, a tappy valve is a happy valve. :i_am_so_happy:
Quote from: NJona86FJ on March 27, 2013, 05:50:22 PM
Is it just me or when you dont play with things mechanical for a while your head goes fuzzy?.... you know brainfade an all that.... must be the blonde
lol
Don't worry Mate I've got it too, only it's not the blonde................it's the Gray :cray:
Thanks to all for clarification, well aware of reasons for burnt valves - changed hundreds when I was in the trade but some years ago now :hi:. Steve, since there is apparently no need to change mine, I won't measure shims now but when/if they need to be removed will do so just out of interest. :pardon: :i_am_so_happy:
VSR is obviously a later issue, given leaded petrol prevented it back then I guess. Thanks for the link Rich :good2:
Take your point Noel and am quite happy to take the experienced view, just wasn't quite sure what that was. Happy I do now though :good2: