Effects of valve wear in relation to valve adjustment

[url=https://www.classicgoldwings.com/forum/viewtopic.php?p=94326#p94326:2z48zbk8 said:

C5Performance » Fri Aug 30, 2013 12:19 pm[/url]":2z48zbk8]
no previous threads discussing valve wear and how it relates to adjustments?

I can start one if you guys want to know more.

Click to expand...

I went ahead and started this thread to discuss how normal wear of the valves themselves can cause a valve adjustment to go all wonky. I understand that as the valves slam back onto the seats, they beat each other up, and the valves retreat farther into the head...effectively making the stem end "longer", and tightening the adjustment. But, at the same time, we also have wear on the cam lobes, rockers, and the stem end of the valves. Which wears faster, or more?
Let the discussion begin! :good: opcorn:

I am not going to get into drag racing or land speed engines. All posts from me relate to street driven mostly stock engines, ok?

You will see minimal wear on a valve seat, and the greatest wear on the valve. The seat surface is extremely hard, and is pressed into the head during the manufacturing process. Valves are a softer material and probably due to a valve being easier and cheaper to replace.

Here is a picture showing a "new" valve and below it one that has excess wear.


Cam lobe and rocker (where applicable) surfaces do show signs of wear in older engines but if the oil film has not been compromised there should not be any wear on those surfaces. Once you "wear through" the hardened cam lobe or rocker surface the engine will only last a short time. Expect to see much increase in metal shavings in your oil pan and filter.

So the rule of thumb is "most" wear comes from the valve edge getting flatter (thinner) causing the valve to sit lower and lower in the valve seat.
A lesser amount of wear comes from the seat, which will be come wider as it wears, adding to the loss of clearance.
These factors reduce the amount of free play at the thin end of the valve, and if clearances are reduced to zero, the valve can no longer close.
Here is another picture showing the valve sealing surface has reached the top of the valve. A new valve would show the sealing (shiny) area closer to the center of the valve.


Since LESS clearance reduces audible noise, you CANNOT tell if your engine needs an adjustment unless you physically check them with a feeler gauge.

If your engine gets louder, and you measure an INCREASE in valve clearance, that can indicate several things:

1) On threaded type adjusters there may have been some movement due to poorly tightened lock nuts at the last adjustment
2) The wear on the cam lobe or rocker arm was greater than the wear of the valve into the valve seat causing a NET increase
3) The valve stem got shorter...in my experience this would only occur if the valve was physically bent. I have yet to measure one that got shorter under normal operating conditions, although i have never measure a sodium filled valve. to see if they shrink in length.

Larger clearances many times indicate the beginning of a failure. If you find one valve with larger clearance, write it down. If you need to adjust valves again and the same valve clearance is again larger, typically that would indicate you have worn through your cam or rocker and i'd personally be taking the top cover off for a physical inspection SOON.

This should get the conversation started. I used general information taught by manufacturers and my own experience at the dealership. There are situations where the information i have provided would not be accurate, but again, for most street bikes, this is how it works.

Let me add my .02 worth........or you can just look at the pictures in this thread..... :hihihi:

viewtopic.php?p=20467#p20467

Thanks for adding that link. I tried finding a burned out cylinder head today but cant remember which storage unit they are hidden in.

I'd like to show a valve and seat that are well used, and then another with freshly lapped surfaces...it really is night and day difference you can easily see in photos.

For those of you who have never seen a really mushroomed valve, you can actually cut yourself on the edge they get so sharp.

Here are some pics from that engine. The valves were razor sharp:



How's this for worn seats:

OMG those are AWESOME pictures!!! Thanks for sharing them to help us out.

Look at how sharp the edge of your valves looked. Amazing amount of wear, but think of the pounding they take.

For those unfamiliar with engine rebuilds, the seats (the outer sealing surface where the valve mates with) should have a smooth, even appearance. When lapping valves for re-assembly, they will not actually be shiny, but they sure won't be pitted and chunky.

I added arrows to clarify.

Yellow arrow shows a shiny seat, which would have a good seal.
Red arrow shows what lack of valve clearance, oil burning, or poor ignition can cause. This seat was not sealing!

FYI - just so members don't get too scared that their engines are in the same shape as this one, that engine had over 169,000 miles on it (some much harder than others). It was a worn out '81 engine with rod knock, razor sharp valves, weak valve springs, worn out big end bearings and rod bearings, worn down piston skirts and loose wrist pins. (Other than that, it ran like a clock!!) :hihihi: I'm not kidding.....up until I pulled it out of the bike, it started instantly, did not burn oil and ran like a clock other than the rod knock at higher speeds!!

I did a thread on it here for those who want more information:

viewtopic.php?p=56923#p56923

If its OK, to talk about a car engine in this forum, I would like to take the Volvo 5 cyl as an example of how much stronger the valves and seats has become. When I worked with cars, every car needed a valve adjustment when they had an oil change done, every 6000 miles (10000) km. Except a few , like Alfa Romeo and some others with shim adjustment. This is the 70s.

Since 2002 Volvo removed the hydraulic lifters, because they say that there is no need. The valve lash is set with shim from factory, and there should be no wear in at least 200 000 miles. I had an 1995 5 cyl. with hydraulic lifters. For sure they could rattle for 30 seconds a cold winter morning. (The engine had around 150 000 miles). But I liked the silence from the valve mechanism when hot.

Now I have a 2002, (160 000 miles) and there is a slight ticking. Is this because of wear? Was it like this straight from the factory? It irritated me in the beginning, but since I learned how difficult it is to shim the valve lash I just live with it.

Out of topic a little there. I just wanted to point out how much improvement have happened to the steel they use in valves, and seats.

I think it is fine to use cars as an example. I agree that modern materials reduce service intervals to an amazingly long time.

Please allow me to use a another "non Honda" example.

Yamaha recommends first valve adjustment on their R1 motorcycle at 26,600 miles. The same engine is used in the Apex snowmobile with recommended inspection at 25,000 miles. This is an engine that runs just under 11,000 rpm for well over 75% of its life.

It is difficult to imagine this since my Ural gets adjusted every 1,000 miles and never exceeds 5,000 rpm.

Now to really blow your mind:

If your Apex averages 10,000 rpm then your engine is turning 600,000 revs per hour.
Assuming you run an average speed of 40 mph it will take 625 hours of run time to accumulate the 25,000 miles needed for the FIRST valve adjustment.

625 hours x 600,000 revolutions per hour = 375,000,000

That means your crankshaft rotated 375 MILLION times at 10,000 rpm before you reached the first valve service.


How's that for reliability?

Impressive, for sure.

[url=https://classicgoldwings.com/forum/viewtopic.php?p=138611#p138611:qc1uiqo0 said:

El-Anders » Sat Jan 03, 2015 3:09 pm[/url]":qc1uiqo0]
If its OK, to talk about a car engine in this forum, I would like to take the Volvo 5 cyl as an example of how much stronger the valves and seats has become. When I worked with cars, every car needed a valve adjustment when they had an oil change done, every 6000 miles (10000) km. Except a few , like Alfa Romeo and some others with shim adjustment. This is the 70s.

Since 2002 Volvo removed the hydraulic lifters, because they say that there is no need. The valve lash is set with shim from factory, and there should be no wear in at least 200 000 miles. I had an 1995 5 cyl. with hydraulic lifters. For sure they could rattle for 30 seconds a cold winter morning. (The engine had around 150 000 miles). But I liked the silence from the valve mechanism when hot.

Now I have a 2002, (160 000 miles) and there is a slight ticking. Is this because of wear? Was it like this straight from the factory? It irritated me in the beginning, but since I learned how difficult it is to shim the valve lash I just live with it.

Out of topic a little there. I just wanted to point out how much improvement have happened to the steel they use in valves, and seats.

Click to expand...

It likely was ticking from day one. Slightly loose AKA properly set valves, will tick. I love that sound. When they get quiet it's time to worry. Just like little kids.

[/quote]It likely was ticking from day one. Slightly loose AKA properly set valves, will tick. I love that sound. When they get quiet it's time to worry. Just like little kids.[/quote]

Your right! When it is quiet, its time to worry