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Valve timing ES2


I'm checking the valve timing on an ES2, 1961.

The book "Norton Singles" by Roy Bacon states that the timing should be: 

Inlet open - 30deg BTDC (mine is 60deg)

Inlet close - 75deg ABDC (mine is 135deg)

Exhaust open - 78deg BBDC (mine is 105deg)

Exhaust closes - 35deg ATDC (mine is 60deg)

Opening/closing point taken as just as the push rod ceases/starts to rotate.

Degrees measured are on the crankshaft.

Interestingly, a website I have just looked at (Performance Pushrods ) mentions values similar to mine for the racing engines!! I don't for a second believe mine has racing cams!

What's going on, where have I been stupid? Do the values refer to camshaft degrees?



Hi Richard,

   Are you sure you have set your pointer at exactly TDC on the firing stroke, i.e. both valves closed. With the head fitted, this can be difficult to find and you might need to check this a couple of times to make sure it is accurate. Make sure the degree disc is bolted tight on the crankshaft and not slipping and also the pushrods are set to their minimum clearance. When you are sure you have all this correct, mark the disc top and bottom as it can get a bit confusing as you turn the crankshaft a couple of times.


But many manufacturers quote lift start and finish points at a certain amount of lift, not fully closed.

For example, my Morini uses readings with a valve lift of 1mm from closed. Ford used to use readings from 0.75mm lift from closed. In both cases it was to ensure the quietening ramps didn't make a mockery of the readings.

Someone on here will know how Norton went about it.


Richard. What made you check the valve timing? It is an unusual thing to do, unless you suspect something is amiss. Any symptoms; background to any issues etc?

Otherwise, a severe case of lockdown boredom, perhaps?


.... I have not been happy with the engine from the startup after rebuilding. Difficult to start hot or cold, spitting back and sounding flat when on the road (I've only done about 20 km).

I remember reading - I don't know where - when rebuilding an old bike when you don't know the history,  you should carefully check that the bits you've been given. Already I've found - usually the hard way - that the distributor is wrong, comes from a twin, the stator is wrong, comes from an early Triumph (?) with two coils of high voltage, four with lv, lighting switch is wrong from something else, both mudguards are wrong, too deep, the mudguard stays aren't correct, the front fork sliders are wrong, bridge mounting studs are about 35mm too high which caused the mudguard to hit the frame and put a dent in my nice new paintwork, I never did get the seat to fit properly, and so on.

You're all going to say I'm a lunatic, but I do like a technical challenge. 

So I decided to check the valve timing because of the article I'd read.

Thinking about it and measuring again, based on the fact that the values I've measured are generally about 25-35 deg extreme, (ie opening difference is too early opening and closing is too late closing, it seems certain that the point at which I have taken to be the opening or closing point is incorrect.

I assumed that as soon as the pushrod upper cap could no longer be rotated, that the valve was opening. That's obviously not correct.  The cam has to exert further force on the push rod in order to overcome the mechanical "slop" in the push rod, the rocker, the valve spring etc. In other words, to compress them minutely so they loaded sufficiently to overcome the spring force. With a cam with a very gentle quietening ramp this will be quite a few degrees of rotation.

So I was hoping someone could tell me just how the factory/workshop would actually measure that a cam is as design - as the values in the Bacon book.

Of course the cam timing has been set by lining up the marks on the cam wheels but I wanted more assurance than that. It is impossible to set up a dial gauge on the rocker.

Having thought all this through, I still don't know how to measure the valve opening point .


On the twins, irrespective of what camshaft is fitted, and what the normal running valve clearances would be, you set the valve clearances to 0.016" in order to check the camshaft timing, then use a timing disc, as you have, and a dial gauge on the valve stem.

What the clearance should be set to for checking the valve timing on a single I don't know, but rest assured Mike Pemberton no doubt will. He is the man to ask. 

Btw, your hard starting a flat sounding symptoms indicate the ignition is retarded, I would say.


...for your assistance. Unfortunately, the single does not have a valve clearance, the screw socket fitting at the top must just rotate freely. So there is no gap to measure.

I have Mike Pemberton's viseo, he sets the valve timing using the marks on the gear wheels.

As no-one seems to know a method which can be used, I'll assume the cams fitted are correct - they probably are.

Thank you again.


The valve timing on late Norton singles is notoriously variable, and the marks should not be viewed as anything more than a starting point. The difference it can make is the difference between a lively bike and a slug.

I made a fork out of 1" x 1/8" strip and sandwiched it between the pushrod and locknut so that I could feel when the backlash took up and the pushrod was gripped, from this I wrote down all the figures I got and decided to advance my inlet cam by 1 tooth from the marks, this made an immediate improvement to starting, tick-over and road performance on my M50. It still isn't right, but when I get around to it I shall try some of my spare cams.


... I don't quite understand. The ES2 does not have a gap into which a strip can be inserted.

Its end is a cup into which the ball end of the rocker sits.

Is the M50 the same or does it have a conventional gap?

Basically however, you are confirming what I heard about these cams.

As I said I sandwiched it between the pushrod and locknut,  if you back the locknut off about two turns or whatever  it will produce a gap. The purpose of this little  tool is just to make it easier to detect when the pushrod is gripped whilst simultaneously turning the engine over (not easy!).

From the published figures and the figures I got I worked out what the median points were and moved mine as near as I could to what it should be. IIRC I tried reversing the crank pinion also to see if that got it nearer.


Richard's exhaust timings are nearly symmetrical about the book values so they look correct. But the inlet opens 30 deg early and closes 60deg late, so it looks like the inlet should be moved 15 degrees earlier so the two numbers will each be near to 45 degrees. If the clearances are opened up, the 45 degree values should both shorten by about the same amount.


...for this insight.

It's obvious when you know the answer isn't it?

I'll check all my measurements again and will adjust as you suggest if they are correct.

Fifteen degrees is 1 tooth in 24. From memory that sounds about right re the number of teeth on the wheel.

Here's hoping!


I advanced the inlet cam by 1 tooth (it's now not on the pop marks) which equals 9 deg on the cam, 18 deg on the engine (the wheel has 40 teeth) 

Although I haven't run the engine yet, it has made a huge difference. The compression is up to 115 psi from the previous 90, and when kicking is over, all the gasping and puffing back through the carb has gone.

Thank you David for your advice.

It's only because I had read somewhere that the cam timing marks can't be trusted that I decided to check them. Otherwise I would never have known, and would have lived with a real dog.

How can it be that the cam marks aren't correct? What was happening in the factory?



You may well have a cam with timing more akin to an Inter or Manx - it is opening early and shutting late. Send a picture of it to Mike Pemberton. The overlap will make it difficult to start, spitty and sound flat at low speeds. It would start to sing above 3,000 rpm.

You should measure the lift and shut points with around 0.010" clearance. The exact figure will be different for different types of cam and whether it has quieting ramps.


Please see the comments above. It is not possible to measure valve clearance on the ES2.

In addition, the inlet valve was opening 18 deg late and closing 18 deg late so the piston only started to compress the mixture when the piston was a considerable way up the barrel.

Hence the low compression pressure.


Hi Richard,

 I have a 1955 ES2 and was surprised that my 600cc Panther was much more sprightly power wise, when the exhaust thread stripped on the ES2 I took it over to Mike Pemberton so he could refurbish the head. I explained to Mike that the performance wasn't as good as the Panther and Mike said check your valve timing even though mine was correctly set to the marks on the timing wheels. He has a special rig for doing it very accurately I had to improvise, I had taken my cylinder barrel off so I had to check the movement of the cam followers (push rod tubes and push rods removed), due to the top of them being spherical I couldn't get a dial gauge to work accurately, so I got a small piece of alloy plate and filed a half circle in the middle of the flat side to replicate the shape of the follower to make a gauge, for the inlet side this sat nicely on the crankcase so by eye I could see when the inlet just started to open, I had a timing disc set up on the crankshaft and found that the inlet was opening too early, I moved the timing dot on the inlet wheel 1 tooth away from the factory mark in a clockwise direction (= 18 degrees on the valve timing), the exhaust wheel timing looked OK. This is a very rough and ready way of checking the valve timing but it worked for me and I'm happy to report that the ES2 is now much more lively and nicer to ride. 

Andy Lodge


... what you have described is exactly what happened with me except that my inlet valve was opening too late. I had to turn the inlet wheel 1 tooth anti-clockwise to advance the timing.

What was going on in the factory?



What was going on was that all the machine tools were absolutely worn out. There is a story that when production moved to Woolwich they kept making a lot of scrap Dominator crankcases because the multi spindle drill which drilled the base stud holes wouldn't work accurately, eventually, in desperation, they contacted the bloke who had operated it at Bracebridge Street (who they had just fired off), and asked him, he said

"Did you take the plank?"

"What plank?"

"The plank that was knocked into the machine to keep it straight".

They were that worn out, I suspect that something similar affected the keyways for the cams and camwheels and they just worked around it by selective assembly, although Mike Pemberton told me that he had a 350 in the sixties which would do a genuine 90, while his mates identical one struggled to make 70, just down to differences in valve timing, and those two were like that straight from the factory.



Hi Richard,

   I think Norman's post is along the right lines. Although there is nowhere you can insert a feeler gauge in the valve train, you can calculate the adjustment. As the pushrod socket thread is 26 TPI, 1 full turn is 39 thou. There are the six flats on the hexagon so each one equates to .0065" or six and a half thou. If you set the pushrod just tight then turn back 2 flats will equal 13 thou which will make sure you are off the cam ramps. 115 PSI sounds too much for a static compression reading which would indicate the inlet valve closing much too early. Below is a post I added to a question on compression readings for a Model 50. The symptoms you describe sound more like fuel starvation.

   In most internal combustion engines the compression ratio is a theoretical maximum pressure calculated on the engine dimensions. In reality this is controlled by the valve timing and engine speed. The inlet valve on your engine closes when the piston is a third of the way up the compression stroke and when turning the engine over at low speed it is only compressing two thirds of the cylinder volume. Bearing this in mind 80 psi sounds quite good, but if you want to see a quick improvement on your gauge, set your inlet pushrod adjuster as slack as possible so the valve doesn’t lift fully and this will bring the valve closing back near bottom dead centre to give you a full cylinder of compression. When adjusted correctly your engine will not get near full compression until it reaches 3,500+ rpm when the gas flow is working at it’s optimum efficiency. This is known as “getting on the cam” or the “power band”. BTW a short stroke Manx has a measured ratio of 11 to 1 but the inlet valve closes half way up the stroke, so 5.5 to 1 on a gauge !


... check the figures again but as your method Richard.

Thank you for this.

BTW, the ES2 has push rods with cup shaped upper ends into which fit the ball end of the rocker.

Is oil fed to these rocker ball ends? Or is it just splash lubrication?

(It would come from the oil supply to the rocker shaft.)


For what it's worth, my 1956 Maintenance Manual & Instructions Book (Publication P92)

States Valve Timing.

Inlet opens before top 19S 11/32" ES2 5/16" M50 11/32"

Exhaust closes after top (same as for inlet)

It doesn't mention anything else about it.


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