modified cdi and cr 80 coil

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
 
flatsteve51 said:
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
Click to expand...

The 750 would most likely work, but you can put two resistors in series that add up to 760 ohms. also you can measure the 750 ohm ones until you find one that is close to 760 ohms.

Remember the value is plus or minus 750 ohms based on the tolerance of the resistor. So if you have a 750 1/2w +-5% resistor it could be as low as 712.5 ohms or as high as 787.5 ohms.
 
brnot I have replaced my spark plug wire at advanced auto parts store. Made hide difference. More power. Better stars and using original Cdi. Along with speed carb and expansion chamber exhaust. It runs like a dream. It's a 80cc schwinn. 28 inch tires. For a road bike it runs great. But yes just replace the wire and u will notice huge difference. Got a 38 tooth sprocket and high performance racing head for more compression on way and my performance upgrades will be done. Can't wait. Should go around 45 mph after that.
 
ivan H said:
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
Click to expand...

Holes like this....

:-||
I had the 27 resistor jumped along with the 100 (which i overlooked because i thought it was the 390)
It was a BRAND NEW piston. maybe 10 miles total, with a small head gasket leak so compression wasn't even as high as it could be.

This situation had nothing to do with the cdi that Dracothered has graciously shared with us, but more so my own error in jumping choices. But with that said, Ivan H sent me some schematics that will hopefully prevent errors like this from happening. Ill be putting them up once i get it drawn up on the computer.
 
Sorry to see you had a melt down there. Yes if you build this CDI make sure all your parts are the right ones and set it to a stock JAG setting at first then go from there.

JP4 & JP5 in the "A" position.
 
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dracothered said:
Circuit diagram
attachment.php


Here is the Board Layout from the parts side.

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Foil side of the board

attachment.php
Click to expand...

Maybe we can all get together and do a group buy and have some blank PCBs professionally made by a board house?
 
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