jaguar
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I just wanted to give ya’ll an update on my CDI mods. To test its reliability I raced my bike Sunday (first moto I had to stop to keep from running over someones nuts! Yeah, the idiot fell, rolled over, and left his legs spread apart! I stopped with my tire resting on his groin! I just got second. Second moto, got the holeshot, and was leading by far until I ran out of gas on the last lap. Arghh!). Anyway I’m feeling more confident about the revised CDI now. In the early stages I had the timing too far advanced and almost seized it. (Upon inspection there was some aluminum left on the cylinder). Of course, having a steel cylinder liner and an aftermarket ignition coil doesn’t help out any. The cylinder just doesn’t conduct heat away like chromed aluminum, and the ignition coil sparks hotter which more completely burns all the air/fuel which creates more heat/power. The other day I received a new OEM stator coil, installed it, and tested its output with the bike running by looking at the signal going to the CDI. Here’s the results:
The positive voltage is 266 at idle and 139 at top revs.
The negative voltage is 4.5 at idle (with the standard 16 ohm pull-down resistor in the CDI). The previous rewound coil was 5.5 v at idle (with 18 ohm resistor). The pull-down resistor controls the negative voltage level which affects the timing curve.
So to experiment I installed the OEM coil and replaced the pull-down resistor with a resistor and potentiometer which could vary the resultant resistance from 16 to 22.5 ohms. That pot was taped to my gas tank so I could vary it while riding. Also the 4.7uf CDI timing cap was left standard for the first test session. It seemed to have the best powerband with the resistance close to 21 – 22 ohms. But the impressive mid range boost of my previous setup was missing. Then I added .5uf to the 4.7uf timing cap (making it equal 5.2uf) and tested again and that oh-so-lovely mid range boost came back when the equivalent resistance was in between 20 and 22 ohms. It seemed that it was able to rev out higher with it near 20 ohms and that the more resistance was there, the better was the mid range boost. But knowing that the boost exists from advancing that portion of the timing curve, I decided to use 20 ohms as its permanent resistance in order to minimize chances of seizure since advancing the timing also makes the engine run hotter. I think I will remain happy with this setup but I really should get a stock cylinder before summer rolls around again in December (yes I am in south america). The heat here is absolutely impressive! Anyway I burned out a transistor in my new timing light so I can’t update you with a timing curve graph right now. Soon I’ll have it fixed.
Look at http://www.geocities.com/a57ngel/moto/CDI-mod.html to see a relative timing graph of the old and the new curve.
:cool:
The positive voltage is 266 at idle and 139 at top revs.
The negative voltage is 4.5 at idle (with the standard 16 ohm pull-down resistor in the CDI). The previous rewound coil was 5.5 v at idle (with 18 ohm resistor). The pull-down resistor controls the negative voltage level which affects the timing curve.
So to experiment I installed the OEM coil and replaced the pull-down resistor with a resistor and potentiometer which could vary the resultant resistance from 16 to 22.5 ohms. That pot was taped to my gas tank so I could vary it while riding. Also the 4.7uf CDI timing cap was left standard for the first test session. It seemed to have the best powerband with the resistance close to 21 – 22 ohms. But the impressive mid range boost of my previous setup was missing. Then I added .5uf to the 4.7uf timing cap (making it equal 5.2uf) and tested again and that oh-so-lovely mid range boost came back when the equivalent resistance was in between 20 and 22 ohms. It seemed that it was able to rev out higher with it near 20 ohms and that the more resistance was there, the better was the mid range boost. But knowing that the boost exists from advancing that portion of the timing curve, I decided to use 20 ohms as its permanent resistance in order to minimize chances of seizure since advancing the timing also makes the engine run hotter. I think I will remain happy with this setup but I really should get a stock cylinder before summer rolls around again in December (yes I am in south america). The heat here is absolutely impressive! Anyway I burned out a transistor in my new timing light so I can’t update you with a timing curve graph right now. Soon I’ll have it fixed.
Look at http://www.geocities.com/a57ngel/moto/CDI-mod.html to see a relative timing graph of the old and the new curve.
:cool: