I timed the Atlas today

seattle##gs

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still has the Lucas mag. Approx 34 degrees both sides. I think it still has the low compression pistons...what is the optimum timing?
 
I'm in pretty close, then. both sides are equal. If I close the gap a couple of thou then it should be on the money
 
Each 0.001 inch changes the timing 2 degrees in the same direction ... i.e. increase gap - increase timing advance. It is far more important to have gaps equal on both ramps, than to be spot on the specification.

Slick
 
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The amount of ignition advance depends on the knock-rating of the fuel and the compression ratio of the motor. Changing the advance can require changes to the jetting.
 
I am lucky that both ramps seem too be the same. I am guessing that the compression is stock due to the relatively easy kick starting. There is no smoke when it starts up
 
seattle##gs said:
still has the Lucas mag. Approx 34 degrees both sides. I think it still has the low compression pistons...what is the optimum timing?
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If still has dished pistons use 32 degrees according to specs, prop auto advance open, don’t forget to remove prop when done
Nortonmark
 
seattle##gs said:
I am lucky that both ramps seem too be the same. I am guessing that the compression is stock due to the relatively easy kick starting. There is no smoke when it starts up
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They are and you only set timing on one lobe, the other lobe is automatically done from first timing point
 
Why is the spec advance for a Commando 28 degrees and for an Atlas - 34 degrees - does it have to do with smooth running ?
 
acotrel said:
Why is the spec advance for a Commando 28 degrees and for an Atlas - 34 degrees - does it have to do with smooth running ?
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The Atlas CR was limited to 7.5:1 to keep the shakes tolerable. The Commando raised the CR to 9:1 .... the shakes masked from the operator by the iso-mounts. I suppose the increased CR required the decrease in timing advance.

Slick
 
nortonmark said:
They are and you only set timing on one lobe, the other lobe is automatically done from first timing point
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As some of us have learned to our cost about K2F magnetos don't take ANYTHING for granted. check timing with bulb and battery/ timing disc on BOTH POTS- everytime!!!!
 
Bernhard said:
As some of us have learned to our cost about K2F magnetos don't take ANYTHING for granted. check timing with bulb and battery/ timing disc on BOTH POTS- everytime!!!!
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+1

If the gaps on both ramps are not equal, there is only one chance in a million the timing will be equal on both cylinders. That is called a 'fortuitous coincidence'.

Slick
 
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Bernhard said:
As some of us have learned to our cost about K2F magnetos don't take ANYTHING for granted. check timing with bulb and battery/ timing disc on BOTH POTS- everytime!!!!
Click to expand...

Yes !!!!!

One sides timing can be a mile out with respect to the other and you will melt a piston.

The error can come from worn lobes but also misaligned magneto shaft or cam ring. Anything more than 2 degrees between cylinders is not good enough. Split the difference between cylinders. I have seen over 10 crankshaft degrees differences.
 
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