Beefed up ignition??

Ok Ivan! That is very interesting information. I've seen that overheated electrode tip before, and never really knew what to make of it! I just went out and checked the plug, and I think I see some possible evidence that it is still happening, even with this new ignition system. I also just finished checking the ignition timing with a timing light. The CDI seems to advance the spark as engine speed increases. I was able to rev the engine very high and the maximum advance I witnessed was about 30 BTDC. This is the setting which seems to deliver satisfactory performance. The CDI controller however does not seem to retard the timing at all; it just advances to a point, then it seems to stop advancing at 30 BTDC, even though engine RPM continued to increase. Perhaps I'll start looking for a CDI which has this advance curve that you and others have mentioned. I chose to try this DC fired CDI simply for the reason that I didn't know how to hook up a AC fired unit to our grubbee engines, fearing that the generator output would be an inadequate power source for the more common AC fired CDI, but I could very likely be wrong on that assumption.
Thanks for all the insight!
-Fred

Yes, ur controlling firing with the magneto, & its output votage increases with revs, so keeps advancing. Page 17 of the "Modified CDI & CR80 Coil" thread. There is a hand drawn schematic of a CDI that retards & we can adjust all parameters 2 suit ur specific needs. If u want, contact with me via email thru this forum (others have) & I can send u photo's showing layout etc, & we can get the firng point where u want & same with where the retard curve kicks in & how steep the retard curve is. A CDI cost like, 10 bucks to make. Cheers

Alright guys, thanks. You know, I've been playing around with different timing. Yesterday, I went for a long ride with an advanced timing setting, and started to notice that the engine was vibrating too much for my comfort. Once I finally got home, I put the magnet back on the shaft with the key. Although power went down a little, I much preferred it because the engine felt smoother. This echoes other posts I've read regarding the 'roll your own CDI'. I remember seeing the schematic before. I'll go back and record it on paper. So, let me try to understand; these components should be installed between the magneto and the coil, right? And can you use the original coil that came with the engine kit, or must you use a coil from a pit bike for example? Or, can I install the components between the magneto and CDI I'm running right now?
Thanks a lot a lot a lot!
-Fredhttp://motorbicycling.com/images/smilies/Waa.gif

Comonent r the CDI, go between magneto & a seperate coil, tons on ebay, around $20, CR80 gives hottest spark. If ur plugs showing that center electrode thing ur generating 2 much heat. Chech side electrode (earth). The flat bit should be tan, getting blackish on the curve bit. If its showing greyish deposits, thats aluminium from the piston top. Back off advance til ur plug tells u all good. Cheers

with the redrawn (much easier 2 read) schamatic there is 1 small (important) connection error in the scr's kathode circuit. Check against the hand drawn 1 for correction. Cheers

hey guys so guess noone has still tried the bounce from one into another cdi standred cdi boxes it works very well all i done was opened up the magnetic field a little more and bounced spark from one to another which i believe the current loss is made up a little cause this setup is so cheap and i have tried the jag black box and now that is not on my ride so that all i can say about the retarded or advances i have the right spark to burn all the fuel my china girl drinks and she runs day by day 77kmh nice

I haven't fired up my new build with the Jag CDI. It would be hard to determine how much it helps performance because my new engine build has an aftermarket head, reed valve intake, engine porting, and other concurrent mods.

For those who shell out the $$$ for it, resolder the input and output leads and then secure them with lots of hot glue from a hot glue gun. The solder job on these wires is awful and the builder knows it because he won't warranty the CDI for solder breaks.

What about this: The Jaguar high performance? The copy says it works with reed valves and expansions chambers.

http://www.jnmotorsbikes.com/product_p/jnm1195.htm

I guess those are proving to be not-so-great.