Roll Your Own CDI

rohmell · Nov 28, 2011

The great thing about forums such as this one is that we can all learn from each other's experiences.

I personally have not had a magneto fail on me (yet), and I don't ride in wet weather, but it might be worth looking into sealing or potting the magneto in a similar fashion to what is done to the stock CDI module.

This gas tank sealer can be used for a multitude of purposes in addition to sealing gas tanks, it can be used as a potting compound for electronics:
Caswell Inc. - Epoxy Gas Tank Sealer
I have used this material for sealing some gas tanks that were so perforated by rust, they looked like a screen door, and this stuff sealed it up, can be painted and the tanks are now in perfect condition.

ivan H · Dec 11, 2011

Impression, I noticed from the pics you posted of the cdi u built that the resistors you are using are actually 180 ohm & 820 ohm, not 18 ohm & 82 ohm as called for in the schematic. I imagine this is why you have been having trouble with cooking resistors. 1 watt should be more than sufficient. Also, only the scr would require heatsinking, (tho prbably not). It should be mounted to the heatsink, using mica or silicone insulator, otherwise the heatsink will be live as its connected to the anode of the scr

rohmell · Dec 11, 2011

Good catch on the resistor values.

Ratchetbirds · Dec 11, 2011

Nice catch on those resistors. I hope Impression checks back soon and maybe works again on his project. I got the feeling he was frustrated with his work and decided on a break. He is a very smart young man with great input.
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Well, on to my project <G>. I have been getting frustrated as well and have finally found my last problem. A broken wire, some of the time. Fine when relaxed, bad when tucked away and insulated from water. It was all that was left after replacing everything else. My next incarnation will have no exposed wire connections. That will be with the all-in-one unit I am working on. Well, the test ride was in 23 degree weather. The morning temps for this week are going to be 20 degrees +/- 5 degrees. Ride home temps will be around 30 degrees +/- 5 degrees. I am so excited <G>.

ivan H · Dec 12, 2011

Thanks guys. Thats the beauty of forums, we can all help/learn off each other. Hey Rohmell, u seem like an electronically very switched on guy, any thoughts/ideas on a simple roll your own timing light for experimenting with these cdi's. I have put together a cdi from Jaguar's posts on repairing kdx cdi & posts about his cdi's for china girls, (c thread ''modified cdi and cr 80 coil''), which runs quite well however I need A timing light for further experimentation & as I am on a disability pension find that comercial unis are a little pricey. Cheers guys

rohmell · Dec 12, 2011

ivan H said:
...any thoughts/ideas on a simple roll your own timing light for experimenting with these cdi's....

I immediately thought of the old fashioned timing light that consisted of a neon lamp:

A neon lamp and a series resistance of a few megs should do it for you.

ivan H · Dec 12, 2011

that'll do it, thanks heaps Rohmell. That u share your knowledge with us is a blessing. Solid state electronics is relatively new to me, my expearience is limitted to repairing, modifying & hand building valve (tube) guitar amps, & as mentioned before in this thread, they are still the cutting edge of guitar amp tecknowledgy, & I believe also high end sound systems. Thanks again, I'll post results of experiments

rohmell · Dec 12, 2011

It is very interesting, once a tube is involved with an audio recording, it imparts its 'Tube Sound" characteristics to the audio recording, which is not lost, even when rebroadcast thru an all solid state system.

I sometimes amaze people when after listening to a certain musical passage, I can tell if tubes were involved in the recording, somewhere, and 99% of the time I am correct!

ivan H · Dec 13, 2011

right u r, listen to old blues like Robert Johnson or Son House, or old Elvis recordings & u can hear the warmth of the old tube console & recording equipment. Or an old Hammond B3 organ with all tube driven tone genorators driving a pair of tube loaded Leslie cabinets, think Deep Purple, they are still highly sought after by top artists. Or for a real treat plug any audio devise thru an English Leak amplifier & varislope pre amp or an American Macintosh thru a set of horns with decent cross overs,,, stand back & enjoy. Horns are rarely used as they are very efficient but reproduce peaks,,, tubes are natural compressors

nightcruiser · Dec 13, 2011

I design and build my own guitar amps with all tube circuitry, so yah, there is something special about tubes, for audio at least. But for guitar it is actually all about smooth clipping and overdriving the tubes for the most part, though a tube driven clean channel with a tube reverb is heavenly as well.
McIntosh tube amps are kickin', but McInstosh Solid State amps are pretty top notch as well. As far as I know they are the only company that uses a tube style output section on their solid state amps with an output transformer between the output and the speaker, which has multiple impedance taps to match the load of your speakers. Most solid state amps just output directly to the speaker, but there's something special about the sound of the McIntosh amps that have the output transformers, even the solid state ones. Recently I had a little amp showdown with my friend, we listened to my McIntosh MC2205 VS his Hafler XL600 and his Threshold Stasis amp, he was quite disappointed when my vintage McIntosh won out for smoothest sound test after test. That Hafler excelinear XL600 was supposed to be hot s#it, and the Nelson Pass designed class A Threshold amp is reputed to be among the best and is worth some serious bucks. My good OLD Mac put them all to bed! LOL

ivan H · Dec 13, 2011

yeah, the various shades of power stage distortion & responsiveness that can be felt back at the guitar is unique to tube amps. High gain master volume type pre amp distortion isnt the same tho it has it place in guitar vocabulary. I'm not familiar with newer mac's but the reactiveness of an output tranny deffinitely imparts its own unique sound/feel to any amp. Thats one of the special features of the old fender bassman,,, the interleaved windings & 2 ohm secondry

ivan H · Dec 13, 2011

Hey do u think we're sorta drifting from the theme of this thread? Another great thing about tubes is their so forgiving of how the circutry theyre plugged into treats them. I'm also a big fan of low power cathodde biased single ended class A amps with tube rectifier for classic smooth overdrive & sustain. And yes, tube driven reverb, whether tranny or R/C coupled is just luscious, Hammond triple spring units I especially like

ivan H · Dec 13, 2011

Ok, back to MB ignitions,,,,,, Rohmell, is there any specific type of neon I should use? I just went to the local electronics outlet & the only neons they have in stock are 90 volt pigtail type bulbs, in green, so I figure if I have to order one I may as well get the one best suited for this aplication. Thanks heaps mate

rohmell · Dec 18, 2011

ivan H said:
Ok, back to MB ignitions,,,,,, Rohmell, is there any specific type of neon I should use? I just went to the local electronics outlet & the only neons they have in stock are 90 volt pigtail type bulbs, in green, so I figure if I have to order one I may as well get the one best suited for this aplication. Thanks heaps mate

The 90V green ones are fine to use. Make sure to have a high-resistance in series with it.

ivan H · Dec 18, 2011

rohmell said:
The 90V green ones are fine to use. Make sure to have a high-resistance in series with it.

Thanks heaps Rohmell. Series resistance for use with 240VAC is 270K so I'll start off 15 or 20 meg & just keep dropping resistance 'til its a goer. They're only about 80 cents each so it wont matter if I go through a few getting it right. Thanks mate

Ratchetbirds · Dec 26, 2011

I just finished the "all-in-one" roll your own CDI. I coated everything exposed inside the box with Performix brand electrical liquid tape. Interesting stuff I found at Walmart's automotive electrical department. I could use a smaller box but this was the closest in size I could find. Maybe next unit I could build a box out of plexi-glass, and get it to the exact size I am looking for. The rubber band in the last 2 pictures was put on for while the silicone is sealing down the lid. The biggest thing is that there are no exposed wire ends or terminals. All wire ends are either in the CDI box or in the magneto case. All you see is armored cable. The kill switch wires can be routed into the box through the same fitting as the armored cable. I will probably try it out when weather gets better, or if my ignition goes south again. Still riding to work every day and loving every minute of it.

corgi1 · Dec 28, 2011

just a thought ,will the armored cable allow air in/out of the mag cover so that it can be sealed from water/?

Ratchetbirds · Dec 28, 2011

Thank you for that thought. I am all about keeping dry now. Fitting is a water-tight. Cable has been sealed at the end and shrink-tubed. Shrink-tubed portion is clamped in the water-tight portion of the fitting. At the engine end I bought a special 1/4" pipe water-tight fitting for 12 bucks from Grainger. And the icing on the cake, at final assembly, I open the fittings and squirt it full of silicone as a final protective seal. I learned all these tricks the hard way from recent experiences, and have gotten alot better at keeping the evil water demons out of my electrical. I have 3 weeks of solid riding every day to and from work in snow, mud, and rain. So far no water in my first style of Ignition or my mag box. Fingers still crossed.

Sinistar · Jan 2, 2012

Rohmell do you have these available for purchase? It's broke my CDI and I need a good one thats dependable. I'm a DIY'er but I'm not able to soakup all this info all to well and don't have that much experience making something like this from scratch i.e. what parts are what and how they work together. If you have made any I will buy one I trust your design. I actually have an old power supply from a computer that I pickedup from a thrift store years ago. it could have the components I need.

Thanks

rohmell · Jan 8, 2012

Sorry for late reply, for some reason, I didn't get any email notifications of new posts here.
Currently I don't have any CDIs made. The cold weather here in NY has put a damper on riding, building and testing CDIs.
Maybe one of the other CDI-Makers on this forum can help you out.

Roll Your Own CDI

Are You Going to Roll Your Own CDI?

No, too complicated and difficult.

Yes, but only one, for my own MB.

Yes, a few for my own use.

Yes, many, I'm gonna sell 'em!

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