Valves clearances

[Shane4371]

Please advise me.how does a fj1200 get tight valves?seena to me more wear will cause loose valve clearances.

[red]

Please advise me.how does a fj1200 get tight valves?seena to me more wear will cause loose valve clearances.

Shane,

The cams and followers are oiled, so they do not wear much, over the life of the engine.  The valves "seat" themselves firmly into the head each time, with little or no oil, so the valves are eroding themselves and the valve seats.  The valves are kinda "sinking" farther into the heads, getting closer to the cams.  The valve clearances are getting constantly smaller, until the valves and valve seats need to be replaced, and it all starts over again.  Neither process is rapid, of course, but the cams and followers wear extremely slowly, as compared to the valve faces and valve seats.  The bucket-and-shim valve adjustments allow for very long miles of wear, before it would be necessary to replace valves or seats.

Cheers,
Red

[Shane4371]

I've checked my intake clearances,  if my memory is correct. .011-.015 is the wiggle roomi can barely get .009 feeler gauge between my cam and shim.how does this happen

[Shane4371]

Also if I leave it alone, the more I ride the more it'll wear into specs?

[Shane4371]

So if its that tight /close cold its a lot worse when it warms up?

[Pat Conlon]

Red already explained to you (very well) how you get tight valves.
When you check your valve clearances you do it on a stone cold engine, so yes, if your valves are tight when the engine is cold, they are even tighter when your engine is hot. They can become so tight that they don't seat. You lose the seal. You lose compression. The hot escaping gases will burn your valve and valve seat.

[oldktmdude]

I've checked my intake clearances,  if my memory is correct. .011-.015 is the wiggle roomi can barely get .009 feeler gauge between my cam and shim.how does this happen

Do not rely on your memory for such important information as valve clearances. Check your manual. Inlets; .004"-.006", exhaust; .006"-.008"
metric inlet; .11-.15mm, exhaust; .15-.20mm. You have mixed up imperial and metric measurements.

[4everFJ]

Also if I leave it alone, the more I ride the more it'll wear into specs?

No, as already explained, it will get worse/tighter.

[Shane4371]

I apologize, but I just don't understand the drive train on my fj,I'm measuring the space between the flatest spot on my cams and the shims,correct? It seems to me the less gap the more lift off seat the valve will have,please be patient with me.

[Shane4371]

I ment valve train,

[FJmonkey]

I checked my valves last week and found some loose and some tight. See attached calc sheet. I hope PDF will view properly. On the exhaust side I had loose valves at #1, #2 #3 and #4 (highlighted in yellow in the "Current Gap" row. I also had tight valves at #2 and #3 (shown in RED. This is after 3669 miles. Before that I had many loose valves and one so tight a feeler gauge would not fit. I used to go 10K miles or more before checking valves. Now I will be checking them every oil change. it is not hard to do so better safe than sorry.

Now to measuring cold vs hot. Metal expands when heated. The head expands, the cams expand the valves expand etc... So the gap we measure includes the expansion that will happen when hot plus the extra distance needed to run the valves properly. If the gap is too tight when cold, it might be so tight when hot that the valve is stuck open a little bit. It never closes fully when hot. This will cause loss of power because during the combustion cycle some of the pressure is leaking past an open valve. The combustion gas is supper hot and heats up the valve. Since the valve cannot fully close it is exposed to way more hot gasses than normal and will burn the valve. I hope this helps.

[red]

I apologize, but I just don't understand the drive train on my fj,I'm measuring the space between the flatest spot on my cams and the shims,correct? It seems to me the less gap the more lift off seat the valve will have,please be patient with me.

Shane,

Change "flattest" to "lowest," to be technical (I know what you meant), and that is correct.  Unfortunately, that is the bad news, here.  You do NOT want the valve to get so much lift that it does not touch the valve seat, when hot.  Then the valve would not seal off the hot gasses of combustion.  If there is any of that hot leakage, that valve would get far too hot, and we say the valve gets "burned."  It will look like somebody held it too close to a cutting torch.  That is almost the reality, only the "torch" here is fed by gasoline, not acetylene.

The temper of the valve gets ruined then, and the engine may run badly for a short while, or at any time, the valve may just snap off the stem and drop into the cylinder.  Then the engine may be damaged beyond all reasonable repair, instantly. Valve clearances must be within the limits to prevent such dangerous damage, and still get the best performance from the engine.  Did I say "dangerous?"  Yes, because breaking off a valve can lock up the engine, leaving you with (at best) a bicycle going at freeway speeds.  You may or may not have enough slack in traffic to get off the road safely.

If any valve clearances are too loose, the engine will not run at full power.  You may hear this valve "looseness" as a "tapping" or clicking valve.  As you realize, there has to be enough valve lift to make the engine run well.  Loose valve clearances can also damage the cam, after some time.  Now if the valve clearances are too small, the valve will not fit down properly into the valve seat, causing a loss of compression, then burned valves, then a broken valve.  A good used engine would cost less than fixing the damage caused by a broken valve.

The engine specs in the manual are very important.  The engineers who set those specs do know a lot about this issue.  Understanding is a great thing to have there, and we can help with that, but don't make theories right now about things which you do not fully understand yet.  Getting something like valve clearances wrong can cost you an engine, if not the entire bike.  It can be very dangerous (to you physically) to wreck your engine while running hard in heavy traffic.  Nobody here wants to ruin all your fun; quite the reverse, really.  Everybody here wants to see you riding off into the sunset, grinning.

Cheers,
Red

[Shane4371]

Red thanks for the input.I've orderd my shim tool.aviator Fred I think will help with the process of replacing my shims,via phone conversation. Thanks you all so much,the way our valve train wears blafflrs me.I apologise for my idiousy

[rktmanfj]

Red thanks for the input.I've orderd my shim tool.aviator Fred I think will help with the process of replacing my shims,via phone conversation. Thanks you all so much,the way our valve train wears blafflrs me.I apologise for my idiousy

It's not idiocy, Shane, it's just a lack of understanding.

These guys have done a great job of pointing you in the right direction.

[red]

Red thanks for the input.I've orderd my shim tool.aviator Fred I think will help with the process of replacing my shims,via phone conversation. Thanks you all so much,the way our valve train wears blafflrs me.I apologise for my idiousy

It's not idiocy, Shane, it's just a lack of understanding.  These guys have done a great job of pointing you in the right direction.

Shane,

Understanding will come, no sweat.  For starters, have a look at "burned valves" on Google (just select Images).  You will see valves that are burned, and as a result, these valves can be cracked, chipped, and maybe broken off at the stem.  Easy enough, or click here:

https://www.google.com/search?q=burned+valves&biw=1600&bih=733&source=lnms&tbm=isch&sa=X&ved=0ahUKEwj0rp3R0rLOAhVL22MKHYUeC7oQ_AUIBygC

All of these malfunctions can be caused by valve clearances that became too small, as the valve wore into the valve seat.

You may notice in your engine that the lever pressing the valve open is not pressing on the center of the valve stem.  This is done so that as the valve opens and closes, the valve (stem) gets turned slightly each time.  This constant slight rotation of the valve as it works will keep the valve and seat to be worn evenly, all around.  That helps to keep your valves healthier.

Cheers,
Red