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Post by flavio on Jun 4, 2019 11:15:07 GMT -5
 Hello, My question is during timing the 4 stroke 49cc Chinese toatao sunny scooter and the T mark is aligned to the engine cover rib mark, the cam shaft is correct big hole at 12 o'clock and two small holes at 3 and 9 o'clock dues the raised block on the fly wheel have to be directly under the black pick up coil? Please see my picture, mine is not aligned and I suspect I lost the key way on the crankshaft. So the crankshaft and flywheel is out of sync. |
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Post by tortoise2 on Jun 4, 2019 12:20:48 GMT -5
suspect I lost the key way on the crankshaft. So the crankshaft and flywheel is out of sync. Insert a probe into sparkplug hole to determine piston top-dead-center . . then observe if flywheel T-mark is aligned with case indicator. |
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Post by flavio on Jun 4, 2019 12:59:29 GMT -5
Yes it is. But it will just not start.
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Post by tortoise2 on Jun 4, 2019 13:42:34 GMT -5
Unclear what fuel-spark-compression troubleshooting efforts, or engine modifications, you have made? Posting images sometimes helps others speculate . . example. |
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Post by snaker on Jun 4, 2019 14:59:27 GMT -5
Show a better photo of any etching on the flywheel. Most will have a T with a hash mark next to it and a F with a hash mark next to it.
The T mark does not tie into the ignition. It indicates the piston top dead center position.
The F mark is the ignition timing indicator. The F is positioned a certain amount of degrees from the T which corresponds to the degrees of ignition timing advance.
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Post by GrumpyUnk on Jun 5, 2019 11:36:57 GMT -5
The F mark or bump indicates somewhat, repeat somewhat, when the spark will happen. The pickup is located 'after' the TDC mark, visually, but in actuality, it will see the bump on the flywheel at some point before TDC. The amount before is 'spark advance' or 'timing advance'.
IOW as the T mark approaches the crank shaft mark/rib, the F pointer approaches the timing pickup, and actually gets to the 'bump' before the T mark gets to the rib marker. Advanced, so to speak.
Re-stating again, the 'bump' will be PAST the pickup when the T mark is aligned.
If you have an AC CDI, several things happen for sparkage. THe flywheel generates some AC current fed to the CDI, which charges a capacitor using the AC through a diode(I think). The charged capacitor sits for a few milliseconds(depending upon rpm) and is finally allowed to feed juice to the coil when the 'trigger' bump passes by the pickup. The pickup generates a pulse when the bump gets there, and the pulse pulls the trigger on a silicone device(transistor, thyristor, triac, I dunno), and the juice charges the coil, the coil creates a magnetic field. The field then collapses when the CDI juice is removed(discharged) and that causes a spark to be generated which goes out of the coil, down the wire to the spark plug, where it jumps the gap, and maybe ignites a fuel:air mixture. Several thousand times a minute. I know the details are not totally correct, but there is a lot of stuff going on in the flywheel/stator charge winding/stator CDI winding/pickup area.
tom
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