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stevec314

stevec314

Member
Just wondering. I know that on some of the really old bikes they had a timming advance. What came along later that eliminated the need for this??

Steve
 
The automatic timing advance was a set of pivoting spring loaded weights usually sitting behind the points backplate as the engine speed got faster the weights would be forced outwards by centrifugal force however that force was controlled by the springs as the weights moved then they would adjust the ignition timing by advancing or retarding dependant on the engine speed
But things have moved on since then

Brian
 
stevec314 said:
Just wondering. I know that on some of the really old bikes they had a timming advance. What came along later that eliminated the need for this??

Steve
Click to expand...
I know I'm gonna miss several "generations" of advance mechanisms but:
*First was a cable from the left grip to the distributor, twisting advanced and retarded the spark.
*Then "flyweights" or "bobweights" were fitted to the distributor rotor. As they spun, centrifugal force pulled them out to change the timing with rpm. springs returned them as rpm's decreased.
*The first electronic ignitions had 2 slots in the rotor that controlled the advance (magic in my unlearned mind).
*Next gen. electronic ign. used a VOES (vac.oper.elec.switch) to advance the timing according to intake manifold vacuum.
*Twin cams ignition timing is controlled by ECM and hundreds of variable signals from various sensors (SERIOUS magic to my unlearned mind).:laugh
 
Yea, what Brain said, then it went to the VOES system electronically advanced by manifold pressure & ignition modules and then into the ECM map still reading sensors doing it electronically like Hopple stated.
 
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