What voltage required at coil for ignition??

bennecc

XS650 Enthusiast
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I noticed something today while I was fooling with my bike trying to get it to start...it may be completely normal but I'm not sure. I'm getting 12.08 volts on the ignition circuit as it leaves the fuse box. At the coil, I'm only getting 11.62 volts. I cleaned the connection (all wiring is brand new anyway) but still get the same voltage drop.

Is 11.62 volts adequate for ignition? The coil, wires, plug caps, and plugs are pretty new. The coil is the standard dual output one from MikesXS that came with my Pamco system. There is spark when I kick the bike over, I'm just not sure if it is "fat blue" spark like my manual says it should be.

spark.png
 
The way you have it drawn, the only possible reason for the drop is a bad (dirty, bad crimp, loose, or etc.) connector. If the connector wasn't there and it was just a continuous wire, it would measure the same at both points. Likewise if the connector had the low resistance of a continuous wire it would measure the same at both points.
 
Yes, that makes sense. I tested the "female" side of the connection while the wires were connected (by testing the back side of the connector) and it also gets the 11.62v. When I disconnect the wires, the "female" side goes up to 12.08v. I'm not sure if that is normal or not. I'll resolder new connectors since I've tried everything else.

Is 11.6v at the coil enough for the motor to start up?
 
hey hotrod, you need to google "ohms law" your nasty old corroded 25+ year wires have high resistance and it's consuming your voltage. and yes, 11.6 is a tad low for the coil.
 
Even with a continuous wire you will have voltage drop. Increase the wire guage to have less voltage drop. The real issue is the 12.08v at the ignition switch. You should have closer to 12.8 at the battery and just a bit less after the switch. Still, you'll be fine with what you have at the coil. It'll work with much less.

Posted via Mobile
 
There wouldn't be a practical drop in that circuit unless the wire was very long. But I think when he explained further he really means the drop is present when the coil is connected, and the connector is okay. Probably current consumed in the ignition box he's using.
 
hotrod? Anyways, as the first post says, all the wiring and connectors are brand new and they are all soldered.

I'm not sure what to think. xjwmx, the drop is present when the coil is connected, but it is still at 12.08v coming out of the fuse so i don't think it is the ignition box. Like I said, I'll replace that connection and see if that helps.

Anyways, I was just trying to determine if the spark I was getting was adequate. Frankly, I'll worry about things like voltage drop after this thing starts back up. For some reason it stopped starting a few days ago and for the life of me I can't figure out why.

Thanks for all the resposes.
 
bennecc,

The PAMCO ignition system has been tested to work all the way down to 5 volts. The electronics actually will work down to 3 Volts, but the coil does not get enough current that low. This is one of the reasons why the PAMCO is a popular choice for batteryless PM systems that start off with zero volts on the capacitor and are lucky to get 8 volts briefly with the kick starter.

Here is a video of the PAMCO driving two spark plugs with a 6 volt latern battery:

 
Thanks Pete. In the interest of trying to eliminate all the possibilities one by one.....I'm not convinced that the spark I'm getting looks like it should. I don't know, its pretty hard to tell from videos on the computer compared to looking at it in real life. But, I would describe the spart I'm getting as white, but definitely not "blue".

Would weak spark on both sides indicate a bad coil? It was recently replaced with the regular dual output one that came with your ignition system. Could I have somehow suddenly damaged the coil? When the bike was last running it was just temporarily hooked up to the battery and the vibrations on the center stand caused the wire to come off the battery, killing the motor. Could that have potentially done some electrical damage? If so, what should I check? I checked primary resistance on the coil which was 4.5 as listed on mikes website. I couldn't find a spec for the secondary on this coil, but I measured 16.5k.....thought that might be high, so i hooked up my good stock coil, but it didn't seem to help.

Of course, at this point I'm second guessing everything! As in, maybe I need to clean the carbs a third time, maybe I put them back together wrong, maybe compression is low, maybe.......and on and on.

Thanks again for all the replies.
 
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