Someone learn me about valve clearances.

All -

I just checked out the valve clearances for my '96. Factory specs are as follows, IN- 0.006 in. EX- 0.010. in. +/- 0.001 in.

All of my intake valves were within spec - 0.005 to 0.006. Seven of my exhaust valves were 0.009-0.010, one was 0.008.

Do I need to worry about the one that measured out at 0.008?

I have read that loose valves are better than ones that are too tight. I assume that this one that is 0.001 out of spec is too "tight"?

 

"Tight" is the correct term. Is it a full .001" less than optimal, or something in between? FWIW, some auto parts stores carry feeler gauges that are tapered in .002" increments which come in real handy for determining that sort of thing. I have one valve on my SV that is less than about .0002" - .0005" tight, and I'm not inclined to pull the cam and associated cam drive bits over that (real tough to get to).

If you're in the habit of long, full throttle running, it would be more of an issue than just occasional sportiness. Exhaust valves get pretty hot compared to intakes, and they need as much time as possible in a fully-seated position to transfer their heat to the cylinder head. On a long, hard pull they can expand enough to take up a lot of the available clearance, although I have no practical knowledge of what that expansion might be. Where I am going with this is that if it less than .001" from the suggested clearance, I personally wouldn't sweat it too much. If it is .001" or slightly tighter, I'd re-shim it. If you choose not too, it might be a good idea to check it after about 5K miles just to make sure it isn't tightening up.

I realize that I'm saying both "Yes" and "No", but it's kind of a personal judgment call. Some will say yes, some will say no. All of my vehicles occasionally find redline in a few gears, but not that often, so I tend to be less fanatical about some things. But then again, I stay on top of the normal maintenance items, like oil & filter, chain lube/adjust, tire pressure, etc.

I'm not sure that this answer is helpful at all, but I'll leave it since I typed it. :smile:

Oh, I should also mention that too loose can be a problem because of the lifting and closing "ramps" that are part of the camshaft lobe. They are there to gradually accelerate and decelerate the associated valvetrain. If the clearance is too great, a portion of the ramps will be missed and the valvetrain will be less smooth in operation, as the parts are being "hammered and slammed", for lack of a better way to put it.

 

Yes it is of concern.
It will not get better.
When the valve is "tight" it means that the valve is not coming all the way up and touching the seat fully allowing the valve to dissipate the heat into the cylinder head and out into the atmosphere through the cooling system and engine cylinder head casting.
If you get that valve in spec the engine will idle smoother too. You can hear the difference.

 

The problem with valves getting tight is that they won't close completely and if you leave it like that for too long you could have a melted valve from all the exhaust leaking out. Not only that it'll be harder to start on a cold day.

 

If you brought your bike into my shop and were paying me your 'hard earned'...I would change it. Mainly because that's my obligation.

If it were my own bike I'd let it go, make a note of which one it is and see how it changes in the next 16K interval. If it were .002 out or more I'd probably swap it out.

Either way, you're never gonna notice any difference in the way your bike runs and at .008 I tend to think you have plenty of 'safety' margin.

 

I have a full set of feeler gauges (the kind fold out of a metal handle and have 30-40 strips of metal in varying thicknesses).

OK, for the exhaust valve that was out of spec:
The 0.009 feeler would not go in between the cam lobe and the lifter. The 0.008 feeler went in freely, and was definitely much thinner than the gap (no "grab" on the feeler at all). If I were to put a guess, it was closer to 0.009 than 0.008. For the sake of having a "definite number", lets call it 0.0085. If I was thinking at all - I would have stacked the 0.007 and the 0.0015 feelers for a definite measurement.

I don't run my bike hard frequently, and I am well aware that this will not "fix itself".

I guess my main question is whether or not this will be OK for the next 3k miles or so...

 

For your particular settings I wouldn't worry about them. The tight valve will close all the way. That .008" gap may close up to .006 when hot. When a cam is made it has certain specs for duration,lobe center angle, seat time etc. These specs are give with a certain lash size for solid lifter cams. The lash is spec'd for the type of ramps the cam has. Such as yours,actually most all bike engines. By changing the lash tighter or more lose you can change the characteristics of the cam some. Car engines that use .022 lash is what comes to mind. You basically can lash .006 either way with out harm to most cams to change power characteristics. This is just a rule of thumb. With your engine as Dizzy said I would not worry about it. Just keep record of the measurement for further reference. Your not going to hurt anything and won't notice any difference in your power. But it's your bike. If your doing the work yourself it may be a learning exercise you want. If your paying for it, it can also be a learning exercise in spending unwanted money.

 

Don't fret about that .001", and do not heed any who suggest the valve won't seat properly.

If your .008" feeler was loose, then consider that the actual clearance is off only about 1/2 a thousandth.

Ok, your bike has how many miles on it?? And in all that mileage you lost only 1 thousandth on one valve, so you see they don't chage much or change fast.

 

Since it's shim and bucket, I'd let it ride but check it in 6k miles or so, unless you run it hard and hot.

 

Sorry - I neglected to mention how many miles - 21,349 as we speak...

 

It is your bike and your money. You can just pretend it is ok.
What about this:

"Pretend" you are a professional mechanic. It is a customers bike.
OF COARSE YOU WILL MAKE IT RIGHT. YOU ARE a PROFESSIONAL and a real man.
You keep your word. you do what has to be done, you tell the truth and do the right thing.
You can tell the owner of the bike "I did your service properly and you do not need to worry."