When the engine is running, the flywheel spins in either a clockwise or counterclockwise direction (depending on your engine). The flywheel is attached to the crankshaft. We won't go into great depths on how the CDI produces the spark, or how electricity works in general (we are only interested in getting the spark to happen at the appropriate time) but I will glance over the important parts that relate to the timing. Stator plate with coils and pickup/hall sensor (as opposed to a points stator plate, which has points and a condensor).Flywheel (internal rotor, or external rotor) with magnets. Lets look at the parts of a CDI system and how they work. Recently, advances in electronics have introduced the CDI (Capacitor Discharge Ignition) which is what we will examine here. This has been achieved by using a mechanical system called points ignition for many years. Adjusting when this happens is very important and can significantly affect how the bike runs. Timing a bike refers to setting when a spark jumps the gap between the center electrode and the ground electrode on a spark plug and its relation to the rotation of the crankshaft. Videoįor people who like videos, an alternate timing method than the one explained below can be seen in this video. I've also found that there is generally only a very small benefit to complex advance curves on basic engines as opposed to an almost immediate ramp up to full advance at relatively low (read starting) rpm.CDI Timing for Mopeds 101, originally posted in the forums. As rpm increases, the triggering threshold advances along with it, some sort of 'effect' evidently. On a side note, I've found in my travails of adapting somewhat more modern ignition systems (ike GM HEI) to older m'cycles that some types of very simple magnetic based pickup coils seem to provide an inherent advance curve as a byproduct more or less of their physics. Saws don't usually have a lot of extra real estate to do that, some do though. Problem with not having to adapt a coil and/or pickup to every different saw and using the stock self contained/triggered coils is that the SCR or whatever that triggers the field collapse event is potted in and you'd need access to that stuff to alter/interupt/replace it, typically not fun to dissect without mucking things up.īest shot at real time adjusability short of replacing the coil with an externally triggered one would be a mechanical advance, like on those old outboards, physically moving the coil. That would be Eric's domain, but he's got more than enough on his plate with dyno stuff for the time being. Integrating it into a dyno chart would certainly further streamline the optimization part. Or physically move the pickup, lots of options. Then use any of a number of adjustable/programmable control modules available/intended for car/m'cycle use to adjust the timing on the fly. Coil could be powered off the flywheel but chances are it won't easily adapt so you'd need a battery to power an external coil. It would be feasible to use most any old externally triggered coil and rig a pickup of some sort (optical, magnetic, hall) off the flywheel. I'm at best just a seat 'o the pants hack with the electronicals, learn as I go just enough to get the job done (or not).
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