adjusting valves while hot

Though it goes against everything I've read, I will consider adjusting valves on a hot motor since that is it's normal condition. The Atlas has a clacking that I cannot reduce.
Do valve clearances get wider once the motor warms up? What should they be on a hot motor?

The valve lash will get tighter on most push rod engines. You could adjust one side hot and check again after cool down.

I think tappet noise is one of those don’t worry unless there is no noise things.

rweb said:

The valve lash will get tighter on most push rod engines. You could adjust one side hot and check again after cool down.

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The problem with adjusting valves "hot" is that how hot is the engine? Adjusting at ambient temperature gives one a bit more consistency.

"The problem with adjusting valves "hot" is that how hot is the engine? Adjusting at ambient temperature gives one a bit more consistency."

Yep, and what clearance are you going to adjust the lash to when hot? If you adjust to zero, then the question of "how hot" when you do that becomes extremely critical. IOW, on these air cooled engines, "hot" after a several mile run down the road and "hot" after sitting in the driveway at idle for 10-15 minutes may be quite different. Less than optimum valve clearance cannot damage anything. The opposite is true of insufficient clearance.

Unless you’re in some kind of none standard situation, with a one off cam and / or alloy barrels and different pushrod material, then why is this necessary?

If you have standard engine components, the engine designer has worked out the required tolerances when hot and has then worked backwards to ascertain the clearances required when cold in order to achieve this.

Unless the designer has specified hot settings, you’re completely guessing !

Best to set cold, to the suggested clearances.

seattle##gs said:

Though it goes against everything I've read, I will consider adjusting valves on a hot motor since that is it's normal condition. The Atlas has a clacking that I cannot reduce.
Do valve clearances get wider once the motor warms up? What should they be on a hot motor?

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In a Norton with iron barrels and alloy pushrods, I believe the clearance reduces as the engine warms up.

seattle##gs said:

Though it goes against everything I've read, I will consider adjusting valves on a hot motor since that is it's normal condition. The Atlas has a clacking that I cannot reduce.
Do valve clearances get wider once the motor warms up? What should they be on a hot motor?

Click to expand...

There are many sources of noise from a Norton engine including backlash on the timing chains especially on an atlas also a loose alternator center
Cam wear
Or follower wear
As Eddie says why stray from what Norton worked out unless you have a special barrel or pushrods

Old cars were often set hot. But remember they were liquid cooled.

This seems like a bad idea. Logically, your only approach is to close up the valve clearances until the bike runs quieter. Or maybe it won't make any difference in noise. But the next question you have to answer is how many miles you get before you burn the valves.

I believe there to have been a rather costly 'learning curve' in the past prior to establishing the how to and why things are done on Norton motors..... I mean mine is 48 years young and never been taken down by following their procedures.... Perhaps all of the ones found in pieces were the product of being done differently..... If it looks and smells like 'IT' one should know to not step in it.

Anyway I'm a cold adjust fan.

I was brought a B40 with a noisy top end, the culprit was the crank timing pinion had an enlarged key slot, the nut was loose but held on by the tab washer which then allowed the pinion to move just a little but then widen the key slot from hitting. The clatter was from the movement in the timing pinion back and forth every cycle causing the top end to be noisy.

Fix whatever the issue is, do not paper over the crack.

Here's something to poop on boys:

My straight up motor has a symphony of noises, but it hauls the mail, so I don't care. You can adjust the lash with a warmed up motor, but it would probably rattle more if you used the .006 int .008 ext values. Best just to do the adjustment cold and live with the noise.

You may have divots in the tops of your valve stems. You'll never get the adjustment exact if that is the case. If you can see obvious divots in the tops of all the valve stems maybe try .005 int .007 ext. I ran a 2S at .006 int .008 ext for months and it is supposed to be .008 int .010 ext. Some documents say wider. Didn't break anything running the reduced lash. Point is you aren't going to hurt the motor reducing the valve clearance by .001 if there are divots in the valve stem tops.

Not sure about what Nortons sound like when the bottom end is about to go. I would think it is pretty darned obnoxious sounding and a slightly deeper note than tappets. You might be able to feel it in the bars on a solid mounted motor.

Irrelevant tidbit:
For the smooth ramp JS2SS cam JSM suggests adjusting the lash to .006 when the motor is warm. Whatever that is and then checking the lash once the motor is cold. Once the cold value is determined, use the cold lash value when the motor is cold. Now I just set the lash at .007 cold because I feel like it. Both the exhaust and intake lash clearances are the same on this cam. It does make a little noise. I could adjust the lash to .006, since when I did it the suggested way when warm there was very little difference when the lash was checked cold.

The motor is stock and has never run better. The head was replaced over a year ago, the valve tips are not dented. Try as I might I cannot reduce the valve clatter which is not excessively loud...not like a Triumph. However I've seen several Nortons that have very little valve noise, what's the difference?

seattle##gs said:

The motor is stock and has never run better. The head was replaced over a year ago, the valve tips are not dented. Try as I might I cannot reduce the valve clatter which is not excessively loud...not like a Triumph. However I've seen several Nortons that have very little valve noise, what's the difference?

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Has it had the Thackeray washers on the rocker spindles replaced by spacers? Loose spacers can cause rattles.

seattle##gs said:

The motor is stock and has never run better. The head was replaced over a year ago, the valve tips are not dented. Try as I might I cannot reduce the valve clatter which is not excessively loud...not like a Triumph. However I've seen several Nortons that have very little valve noise, what's the difference?

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There are lots and lots of differences. Some major and some minor, especially with an older engine.
Set you valves to exacting mfg specs. at the temp. recommended. And make sure you have enough oil delivery to the friction points/contact surfaces.
If you are listening to an engine running at proper operating temp. with little of no valve chatter, chances are the lash is set exactly right or is too tight.

There are a whole lot of engine gurus out there who insist on hearing a bit of valve chatter, especially from older engines and will intentionally set them on the loose side.
Why? because they know they are not burning an intake valve having the tappet clearances set too tight.

seattle##gs said:

Though it goes against everything I've read, I will consider adjusting valves on a hot motor since that is it's normal condition. The Atlas has a clacking that I cannot reduce.
Do valve clearances get wider once the motor warms up? What should they be on a hot motor?

Click to expand...

In almost all situations tolerances get tighter as a heat producing power source/engine warms up...heat influence results in expansion.
Cold influence results in contraction.

I am curious why you would employ a contrary and opposing method of adjustment vs. a time proven method.
If you attempt to reset all the valve lash in your hot/up to temp. engine it will change tolerances as it cools, and it will change quickly.
Better wear some welding gauntlets to keep the hot pipe burns of clothing and skin minimal.

You would never set your PSI on hot or even warm tires - you do this when cold because cold is a more consistent and dependable state from which to generate a successful outcome.

Adding heat is just asking for trouble.

Valve clearance was and is not a random value. Chosen for a reason. Some engines have almost zero, just so that pushrods can be rotated, others quite big.
Why adjust cold. Simply because cold means a temperature at which the mechanic usually works. A quite small temperature gap that don't affect clearance noticeable.
On the contrary hot could be a huge temperature difference. As adjustment can't be done on a running engine, the adjustment of four valves can't be done correct as the engine has cooled off much for the last valve adjustment.
The simple task of changing from warm up spark plug to race plug on a warm engine needed blacksmith hands, so the thought of adjusting valve clearance hot don't appeal to me.

Jdub said:

You would never set your PSI on hot or even warm tires - you do this when cold because cold is a more consistent and dependable state from which to generate a successful outcome.

Adding heat is just asking for trouble.

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On race slicks, we always adjust tire pressure just before taking off the tire warmers, immediately before race.

Its just a British rattle, if the bike is running good then everything is good, I know when my valves need adjusting, but its been so long since I adjusted my valves, if the Norton is running sweet I leave it alone and push rod twins will have clatter to me its a sweet sound, its when they are too quiet I be worried, after over 46 years with my Norton I only readjust my valves after rebuild, retorque the head, and only check when servicing, most of the times the valves are always good and my motor has well over 160k miles on it, it was a everyday rider for most of its life but has been semi retired since 2013 when I bought my new Thruxton, but I still ride the Norton regularly.
With the Combat cam profile and headwork that's been done to my motor since the early 80s I adjust my valves between stock adjustments and Combat adjustments and is just right with my hot 850 motor and my bottom end has been all balanced including push rods, con rods and pistons and my British clatter is just right for my ears, I also run a STP mixture in my oil since the late 70s and have had good long life out of my motor and is only on it first over bore the rebore and final hone was done at tighter tolerance than specified.
So do the valve adjustments cold by the book and learn to live with the British clatter as to me its music to my ears.

Ashley