I'm a bit, or maybe a lot, confused about the Ignition (spark) timing on my 1997 787 motor. I had to tear the motor completely down to replace the rotary drive gear and had it bored out at the same time. When I took it apart I obviously had to remove the flywheel and, in the process removed the mag cup. It would have been clever if I had marked its position before removing it but somehow I forgot that step. However, all is not lost. I can see by the markings on the flywheel that it goes in only one of two possible positions, exactly 180 degrees apart, and in both positions one of the two magnets is in exactly the correct position. My question is, can this cup be 180 degrees out? There are two magnets or pickups or whatever they are on the cup but I cannot figure out how they can somehow correspond to a particular cylinder. I just don't think the system is that clever. But the only way I see it working is if both plugs are firing at the same time, which seems a bit bizarre. I have lots of engine experience but this is my first two cylinder two stroke. Am I on the right track thinking that both spark plugs fire at the same time?
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787 ignition timing
- Thread starter Hunterb
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Thanks Chester. I have the manual and the protrusion lines up correctly. I was just struggling with figuring out how it was differentiating between the two cylinders and was worried that I could have the timing 180 degrees out, which happens all the time when working on 4 strokes, but I see now that it doesn't and just sparks both at the same time. Since the cup is back on exactly as it was, or perhaps 180 degrees from what it was, the timing should be correct, assuming it was correct before all of this.
Thanks for the clarification Chester!
Bruce
Thanks for the clarification Chester!
Bruce
That was my thought as well which was why I was scratching my head. I had a similar learning experience a while ago when I was rebuilding a VW Scirocco and discovered that all of the fuel injectors fired at the same time, or constantly actually. Who knew?
GGuillot
Well-Known Member
Note the single ignition wire going to the coil pack. But I think the RFI and DI skis are controlled separately.
Yes the Injected skis are different.
Ckrawiec
Well-Known Member
I assumed there was a magic circuit inside the ignition coil that flopped back and forth to put the fire on each plug wire respectively .... I never considered a wasted spark idea...always learning something....great free education on these forums (if you open your mind to the wisdom
Close, LOL. But never let that magic smoke out of electrical parts.
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