ignition timing
- Thread starter Qside
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Taking a second look at commando cranks.
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.
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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
So on my bike, the key slot is at approx 11 o'clock when my pistons are TDC
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acadian
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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.
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ATLAS crank
At piston TDC
Atlas keyway is around 11 oclock
Commando keyway is around 6:30 oclock
there fore NOT 180 degrees
ashman
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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
Ashley
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It's a "new Lucas rotor".
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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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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?
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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