Coil Repowering Reliability

I'm thinking of doing the coil repowering mod, but I have a couple of concerns. On automotive points ignitions, there is usually a resistor in series with the coil to limit the charging current while running. The resistor is usually bypassed during starting to provide a stronger spark for a cold engine. But the resistor is there, I've read, to improve the life of the coil(s) and points. The stronger spark generated by this mod will put additional stress on the coils and points. I'm not too concerned about the points, since they are pretty cheap, but the coils are a bit more expensive. AND, I don't really want to do anything that increases maintenance. Has anyone had a coil failure after doing this mod? Has anyone noticed the points going out of adjustment sooner?

BTW, after spending a little quality time with my electrical schematic last night, I found that the power for the ignition goes through 9, yes N-I-N-E, connections. So I do want to do this mod if my concerns above aren't an issue.

Thanks.

The mod just restores the voltage to it's original level when new.

Think of it this way:

Your engine will last a lot longer if it never turns over 3500 rpm, if your timing advancer was stuck in the full retard postion and limiting rpm to 3500, would you fix it?

Most motorcycle coils are designed to have a full 12 volts at the coil all the time, most of the automotive coils on points systems were designed to have a full 12 volts at the coil only when cranking the engine.
Different requirements for different designs.

The usual reason for readjusting the points is to compensate for rubbing block wear, not wear to the actual points.

Post edited by: steell, at: 2006/09/19 08:17

On the KZ's, the ballast was used to prolong the life of the points more so than to protect the coils. On cars, the ballast protected the points and the coil like you said.

The wiring mod bypasses the ballast unless you wire it to use the ballast. If you bypass the ballast, you may shorten the life of the points due to the extra heat they have to dissipate which leads to pitting sooner. With points, you want the coils to be about 4 ohms. Or if the coil is less than 4 ohms, you want the ballast to make up the difference to 4 ohms. You can probably get by ok down to 3 ohms.

Like Steell said, the adjustments are more for mechanical wear. When the points pit, one side pits and the other side builds up a bump. To remedy this, you file away the bump, but the overall points gap stays about the same. You you may not be doing more adjustments, but you may have to file more bumps.

Post edited by: loudhvx, at: 2006/09/20 02:03

The 750 twins don't use a ballast, and I don't think the 650/750 fours (KZ's) do either. The only ones I have run across with a ballast is some years of 1000's.
Might be others, I don't know.

steell wrote:

The 750 twins don't use a ballast, and I don't think the 650/750 fours (KZ's) do either. The only ones I have run across with a ballast is some years of 1000's.
Might be others, I don't know.

I think you're right, but for some reason, when I was rewiring a 77 650 C, I came across a big ol' ballast resistor which had a very official-looking mount. Since then, I haven't seen any documentation to show it ever should have had a ballast. I tossed it because we were converting to a 550 electronic system, but assumed it was original. It could be someone tried to put an ignition from a 1000 on it.