modified cdi and cr 80 coil

Just about any single lead coil would work. I think even a car raceing coil would work, too, as long as it has the same wireing. Of course, then again, who needs a coil as big as one of these engines...

zpt
 
Hi, thats exactly wot u want. The CR80 coil gives a really hot spark, better than most of them. The lead from the free end of the charge caps in the CDI goes to the spade terminal on the coil. The earth lead from the CDI goes to the core of the coil with a large eye connector. Cheers
 
Just put mine together tonight, tested it, no spark. Are the charge caps ( i rhink thats what they are....2 biggest things on the board) directional? I'll be re checking all the connections and orientations in the morning.
Also, if jumpers 4 And 5 are left totally open, will you get any spark? I'll be jumping them to jag settings but would just like to narrow down what my problem is.
Thanks for the help in advance!
 
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Glad u found the problem easily. Yes the SCR (silicon controlled rectifier) has a cathode (K), gate (G) & anode (A), & must be oriented correctly, as must all diodes & the 3 tanalum timing caps (the + marked legs go to earth). The large charge caps & all resistors are not polarized & can go in either way. Cheers
 
my scr was reversed, i built the circuit in mirror image to the diagram, but everything seems to still be in the correct orientation, +'s to earth on the timing caps, and double checked the diodes...but still not getting spark.
I do have the 47 and .47timing caps going from the same hole to the ground (got tight on space and figured if they were in the circuit anyways, it wouldnt make a difference, but i may be wrong.
On a side note, what does jumper 2 do? I searched a bunch but am still blank on it
 
Hey guys, if u read thru this thread & the thread about adjustable timing magnets u will find several warning on the dangers of running to much advance. These warnings r 4 good reason, u can easily hole a piston top, do big & small end bearing damage etc by having the spark too advanced. In this & the "roll ur own CDI" thread I have given a couple of ways to know if the spark is detrimentally advanced, but if u r running advanced spark & r unsure u should pull the jug & piston & view the underside of the piston crown. If all is ok it'll be the normal alloy color with an oil coating. If however, it shows black carbon deposits on the underside of the crown, u r running too much advance. The black carbon deposited is burnt oil resulting from excessive heat. Back the timing off. It doesnt take long to pull the jug & piston to check & is much better than replacing ur engine. Have fun. Cheers
 
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k.mah said:
my scr was reversed, i built the circuit in mirror image to the diagram, but everything seems to still be in the correct orientation, +'s to earth on the timing caps, and double checked the diodes...but still not getting spark.
I do have the 47 and .47timing caps going from the same hole to the ground (got tight on space and figured if they were in the circuit anyways, it wouldnt make a difference, but i may be wrong.
On a side note, what does jumper 2 do? I searched a bunch but am still blank on it
Click to expand...

Print off a new copy of the circuit and go through it part by part and make sure they all connect to the right parts in the circuit. As you trace through the circuit use a highlighter marker to trace the circuit as you check the connections. Also make sure you don't have any shorts that connect two areas that are not suppose to be connected.

JP2 is for timing.
 
Hi, if u google "simple SCR test" or "how to test an SCR", u'll find several simple ways to test ur SCR (out of circuit) with a battery & light bulb, to make sure it aint fried, tho i dont think it would be, but u can check to make sure. The jumper 2, when added in steepens the retard curve. Cheers
 
ivan H said:
Hi, if u google "simple SCR test" or "how to test an SCR", u'll find several simple ways to test ur SCR (out of circuit) with a battery & light bulb, to make sure it aint fried, tho i dont think it would be, but u can check to make sure. The jumper 2, when added in steepens the retard curve. Cheers
Click to expand...

found an easy test and took the scr off the board. works great! thanks for the advice!

Went over the entire board double checking that my circuits were correct and that the orientation of anything with polarity was also correct. im getting more solder tomorrow and will be going over everything that needs to be linked together, then using a dremel in the areas that are supposed to be clean to guarantee there are no shorts. hopefully this will produce spark!
 
k.mah said:
found an easy test and took the scr off the board. works great! thanks for the advice!

Went over the entire board double checking that my circuits were correct and that the orientation of anything with polarity was also correct. im getting more solder tomorrow and will be going over everything that needs to be linked together, then using a dremel in the areas that are supposed to be clean to guarantee there are no shorts. hopefully this will produce spark!
Click to expand...

If done per the drawing and nothing is shorted, open (ie: no connection) or was put in the wrong way it should work right out the gate. Check all the connections and make sure the jumpers are in correctly also.
 
GOT IT TO WORK! I had every rectifier backwards, on the ones i bought have the silver marking on the correct side....but also had a diagram with the arrow and + going in the opposite direction.

A note to all those going to build these....go by the diagram, the silver strip on the rectifier needs to match your circuit same as the diagram

SO HAPPY ITS WORKING!!! :D
 
k.mah said:
GOT IT TO WORK! I had every rectifier backwards, on the ones i bought have the silver marking on the correct side....but also had a diagram with the arrow and + going in the opposite direction.

A note to all those going to build these....go by the diagram, the silver strip on the rectifier needs to match your circuit same as the diagram

SO HAPPY ITS WORKING!!! :D
Click to expand...

Congrats... happy motoring brnot
 
Is it possible to use a 0.47uF 50v Tantalum for the one with the jumper? I somehow lost my spare 35v and the local shops only have either 50v or 100v.
 
k.mah said:
Is it possible to use a 0.47uF 50v Tantalum for the one with the jumper? I somehow lost my spare 35v and the local shops only have either 50v or 100v.
Click to expand...

The 50v will be just fine in place of the 35v. Going higher in voltage rating here will not hurt a thing, you just don't want to go lower in voltage.
 
I updated the circuit diagram to show what JP2 does and put an optional kill switch in with a note about the stock kill switch position. Hope this helps all that will build this.
 
Can any body tell me where to find 760 ohm resistors. It's the only part I can't find. Would a 750 ohm work? Thanks for all the info I'm looking forward to building this
 
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