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Norm's 2 stroke repair center Having problems with you 2 stroke motorized bicycle engine? Just ask Norm. he loves to tinker and troubleshoot engines.

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Old 12-03-2009, 10:47 PM
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Doktor Puttz Doktor Puttz is offline
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Question Magneto and spark timing?

What's the deal with ignition timing and magneto position? Is it possible to adjust the timing to advance or retard the spark?

Thnx in advance
Doc
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Old 12-03-2009, 11:05 PM
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Norman Norman is offline
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Default Re: Magneto and spark timing?

nope its set to one spot only non adjustable.
But you can make off set keys to change it, its a pain to do. look at the mag rotor the key way is
even not true to the hole on the mag rotor so the key is going to be ornery to make I tried one and only one so far, total flop. I'll try it again though I went way to far on the advance on the first try.
I've also been tinkering with an adjustable mag coil bracket. to make that work you will have to do some serious cutting on the engines cover to swing the mag coil there just isn't any room to play
with on them.
I should learn to leave things alone and just ride it. but what fun is that?
I wonder if a guy could change the timing by use of some electrical components to alter the current to the cdi?
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Last edited by Norman; 12-03-2009 at 11:07 PM.
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Old 12-04-2009, 11:41 AM
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Doktor Puttz Doktor Puttz is offline
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Default Re: Magneto and spark timing?

If I understand the principle, you can delay a pulse but not advance it. Don't think retarding the spark would be worth anything. Theoretically the CDI induces delay since the capacitor needs a certain amount of time to charge. Charge time ought to be a factor of capacitance, more mfd = longer charge time. Remember we are talking milliseconds here, so it's a totally rotten place to mess around.

I apologize for not looking first, but how is the inductor magnet fixed to the rotor? Is that the keyway you mentioned, or is the key on the rotor itself? Is there enough space to add a rare earth magnet ahead of the existing one? You'd wind up with a longer pulse and (maybe) a longer discharge interval from the CDI. Dunno if that would mean a weaker spark over a longer interval or if it would make a hotter spark due to the extra charge time on the cap. Hmmm....

Doc
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Old 12-04-2009, 12:20 PM
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Default Re: Magneto and spark timing?

the key is a wood ruff key it fits into the slot on the crank the magnet rotor had a key way cut into it sort of off set to the hole. Not a lot of room to modify anything. I was leaning more toward advancing the timing. I know that not all of these engines have the hole for the wood ruff key in the same spot on the cranks some are a little off more than others. I've found on one engine if you turn the mag rotor over the engine won't run did that by accident. I've even played with adding an extra coil handmade to the mag coil for lights either not enough winding or the wrong size wire I can get a light to work but not very bright. I do have a bunch of failures tries just to get one of the coils to work and winding wire on to a post to me isn't fun to do trying to keep it inline and neat etc.
There is a coil you can buy off ebay to add a light coil its expensive but I understand it works good.
Might be the way to go as you might be able to add a charging system and a battery then you would have lights with the engine off and could add these brake light, turn signals, horn, radio or what ever you can conger up to put on the bike.
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Old 04-01-2010, 01:14 AM
highseastravler highseastravler is offline
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Default Re: Magneto and spark timing?

ie found that a dc bias voltage on the ground return line affects the phase of the zero crossing trigger circut with a positive voltage you get advance with a negative votage u get retard
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