Re: msd ignition

• Author: Graham (---.wi.res.rr.com)
• Verified User: mobyman
• Date Posted: 05-17-08 21:26

most moped ignition systems i’ve worked on are simple breaker points ignitions. the primary coil voltage coming out of the stator varies wildly, a bosch ‘6v’ ignition system isn’t 6 volts at all, its more like thirty when you hook it up and measure it. The 12v coils are designed for battery (DC) breaker points ignitions, or in the case of the MSD coil, designed for electronic (CDI) ignitions.
I dont know much about the motobecane ‘12v’ electrical systems, but if they are like the vespa 12v system, the 12 volt coil only drives the lights, similar to the 6 volts in a puch system. The actual ignition coil is some totally different voltage. If you have 12V CDI, then you would be fine running the MSD coil, otherwise it might work depending on what voltage you’re putting out, it might not. The electrical systems on these things are just that-systems, they are based on a collapsing electric field inducted in the primary and secondary windings, and require the proper windings in both the internal and external coils.

I’ve run several puchs over 9000 rpm’s, and currently am running a sachs at over 10,7 and none of them have had any problems with the electrical system whatsoever.

Not to mention, that adding a different coil doesn’t necessicarily improve the spark heat, energy or anything else. The only reason MSD sells their own coils is because (in theory) the windings are made of a higher grade copper that conducts better while making less heat. The only time you need that is when you have a high powered CDI firing tons of spark (msd-multiple spark discharge, fires multiple sparks for each ignition event) through the coil and it begins to heat up.

you can think of coils like gear ratios, the number of turns in the primary, to the number of turns in the secondary, gives you the ratio that your voltage will be increased. You can put a crazy gear ratio on a stock bike, but you wont go any faster if you dont have the power. You can put a different coil on (you should probably know if you are going up or down before swapping also) but if you dont have a more powerful ignition module or primary coil, you wont get any more powerful of a spark.

Hope that helps.