ignition timing

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dynodave said:
Taking a second look at commando cranks.:(
Click to expand...

https://www.accessnorton.com/Norton...-and-atlas-crankshaft-2016.21469/#post-320472

The correct Commando timing mark of an original Lucas rotor would be the one next to 'LUCAS' so is the mark opposite the keyway.

ignition timing
 
Did we determine the relative position of the key way (woodruff key slot) on the crankshaft/rotor with respect to where TDC is? For example is the keyway at 12 o'clock at TDc? I must have a non-standard commando crankshaft in my engine.

So on my bike, the key slot is at approx 11 o'clock when my pistons are TDC
 
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qside said:
Did we determine the relative position of the key way (woodruff key slot) on the crankshaft/rotor with respect to where TDC is? For example is the keyway at 12 o'clock at TDc? I must have a non-standard commando crankshaft in my engine.

So on my bike, the key slot is at approx 11 o'clock when my pistons are TDC
Click to expand...

I've seen primary scales out by as much as 5 degrees, but never as much as yours. You said the gauge looks undisturbed and that the cover is properly aligned to the inner cover when fitted, so I'm assuming that you've also confirmed the inner primary case is properly fitted and aligned? Not missing any of the three case bolts?

If all good there, I would be quick to check TDC with a piston stop and degree wheel on the opposing (timing side) piston with a view to comparing against the primary side.
 
So it's off by 4 1/2 hrs. (Sorry, couldn't resist)
It's going to be interesting to see this get resolved.
Someone probably already has the answer...
 
This picture is of a 1972 Commando crankshaft that has never been apart with a just opened rotor. I tried very hard to have the crankshaft TDC straight up. The timing mark to use is the one near the top (opposite the keyway)

ignition timing
 
Maybe at some point in time the keyway bush has been replaced and a new bush inserted and might have been pressed in the wrong place with the timing marks out of place, my rota centre had been replace many years ago and when I got it back the keyway was cut very shollow and had to file the keyway down for it to fit, but one day I took it to work and used a broch set to cut the keyway deeper, it would be very easy to press in a new bush in the wrong position.

Ashley
 
ashman said:
Maybe at some point in time the keyway bush has been replaced and a new bush inserted and might have been pressed in the wrong place with the timing marks out of place, my rota centre had been replace many years ago and when I got it back the keyway was cut very shollow and had to file the keyway down for it to fit, but one day I took it to work and used a broch set to cut the keyway deeper, it would be very easy to press in a new bush in the wrong position.
Click to expand...

It's a "new Lucas rotor".
 
OK, to be exact my rotor Keyway is at 5 o'clock, not 11 o'clock. Since I am using a Boyer it did not really matter to me if I was on compression stroke or not. Nevertheless, this explains my dilemma. I have an Atlas crank. It looks like I am 1 1/2 hrs behind. That explains my 10-15 degrees off.
 
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I never use the manufacturers' marks on any bike. If the cams have dots, I usually fit a degree disc and find out where the timings are at when the dots are used. Then I proceed from there. If you get the ignition timing wrong by 3 degrees, you can have a substantial problem. 10 to 15 degrees off, is ridiculous. Forget the rotor keyway and the markings and just set it up right with a degree disc and strobe light.
 
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Hello!

I have experienced a shift between the rotor and the hub on my 1973 commando!

I could move the rotor by hand, while the hub was fixed to the shaft.

A ticking bomb!...... I replaced the rotor intstantly!

Benton
 
qside said:
Since I am using a Boyer it did not really matter to me if I was on compression stroke or not.
Click to expand...

Yes, it does. Although the Boyer is 'wasted spark' it only fires once for each revolution of the crankshaft so it has to be timed "on the compression stroke" (pistons close to TDC).

Edit: As it's a (20M3) "68 Commando" with the 'points' housing behind the cylinders, then hopefully, you are timing the Boyer rotor/stator for clockwise rotation?



qside said:
Nevertheless, this explains my dilemma. I have an Atlas rotor.
Click to expand...

If, as you said, the rotor keyway is at 5 o'clock (with the crank at TDC?) then it's the crank keyway that's out of position, not the "New Lucas rotor" of which there is only the one type (54202299) shown in previous posts.
 
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If the rotor was firing the ignition system, you might have a problem. But it doesn't and you don't.
 
Huh, nobody mentioned the early Lucas rotors can spin on the center which moves the timing mark. Later welded rotors don’t have this problem. This is old stuff.
 
Hello!

See my info on shifting/separated rotor on hub above!

My Commando was produced December 1972.

Initially it confused me alot when trying to set the timing.

Then I realised the rotor had come loose from the hub…!!

Benton
 
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