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Lighting and Electrical Things that go ZOT! Ignition components, batteries, lighting and accessories

View Poll Results: Are You Going to Roll Your Own CDI?
No, too complicated and difficult. 27 24.77%
Yes, but only one, for my own MB. 36 33.03%
Yes, a few for my own use. 37 33.94%
Yes, many, I'm gonna sell 'em! 9 8.26%
Voters: 109. You may not vote on this poll

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  #21  
Old 06-04-2011, 05:42 PM
elevator elevator is offline
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Default Re: Roll Your Own CDI

hi there
new to forum but i made a points condenser ignition for ht engine to see if it gave more power and to help idle. the idle was great but no real top end help. the funny thing was atstop signs it would reverse rotation and go in rev, battery lasted 2 hours
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  #22  
Old 06-23-2011, 06:10 PM
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rohmell rohmell is offline
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Default Re: Roll Your Own CDI

Here is the CDI circuit that I have been using:
ROHMELL CDI schem.jpg

Tomorrow, I will take some pics of the completed assembly.
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  #23  
Old 06-23-2011, 06:58 PM
elevator elevator is offline
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Default Re: Roll Your Own CDI

Ok great. thanks for the circuit posting, I never had a cdi go out on a ht but many field coils from water, they were never insulated very well. The main area of needed improvement on a ht ignition was the idle, the cdi stops working at low rpm. The advancer settings never realy helped much on a small two stroke because I experimented with many settings and even advanced it so far it started running backwards using a cam and battery ignition had fat blue spark and would idle perfect.

I ride both ht and whizzers and need a circuit like you cdi one with and advance circuit, around 1000 rpm it advances. The four stroke engine is differant and the advance is very important but not so much on 2 strokes. can you send me a schematic for a cdi with an advancer circuit.
Thanks
Jim
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  #24  
Old 06-23-2011, 07:17 PM
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rohmell rohmell is offline
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Default Re: Roll Your Own CDI

Basically, I am working with the HTs, and their CDI circuits. With these CDIs, it is easy to retard the timing because you can delay the existing signal, which comes from the magnet so that it appears later. Not so easy to advance, because you are wanting a signal to occur sooner than it is available from the magneto. In order to solve this problem, you first have to manually reset the magnet timing to a super advanced state, and then have a wide retard range using the CDI to give you a relative range of suitable advance/retard settings.
Adding capacitance to the gate circuit of the SCR will cause a retard effect.
There is a schematic in this thread that uses such a method (for Kawasaki, I think)
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  #25  
Old 06-24-2011, 10:18 AM
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rohmell rohmell is offline
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Default Re: Roll Your Own CDI

If there is interest, I may consider making more and selling 'em.

Here are some pics of the completed CDIs:














Last edited by rohmell; 10-07-2011 at 07:17 AM.
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  #26  
Old 06-24-2011, 10:21 AM
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rohmell rohmell is offline
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Default Re: Roll Your Own CDI


By rohmell at 2011-06-24

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  #27  
Old 06-24-2011, 11:21 AM
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Skarrd Skarrd is offline
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Default Re: Roll Your Own CDI

^that is pure win!
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  #28  
Old 06-24-2011, 12:23 PM
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rohmell rohmell is offline
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Default Re: Roll Your Own CDI


Last edited by rohmell; 06-24-2011 at 12:37 PM.
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  #29  
Old 06-24-2011, 02:22 PM
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GearNut GearNut is offline
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Default Re: Roll Your Own CDI

rohmell, does yours automatically retard the timing as the RPM's go up?
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  #30  
Old 06-24-2011, 02:26 PM
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rohmell rohmell is offline
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Default Re: Roll Your Own CDI

Quote:
Originally Posted by GearNut View Post
rohmell, does yours automatically retard the timing as the RPM's go up?
There is no R/C network to retard the timing, but it can easily be added. (see other schematics in this thread)
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