KZ650B ignition

New guy here on the forum has a question.

I just picked up a 1978 KZ650B and want to convert it to electronic ignition. I was considering the Dyna S Kit but am asking for advice first. A concept my wife says I need to utilize more often, lol.

I’m an easy ride kinda guy. Back roads to anywhere I’m heading, rarely hitting over 65mph, sometimes the wife is in tow. My KZ has a Vance&Hines 4in1 exhaust and K&N pods. The Dyna S kit comes with race coils, etc, things I may not need to pay for, so what do you think?

Also, it seems like the bike has to warm up or it misfires when I hit I the throttle. Any ideas on why this is happening?

Thank you LexPaul
1978 Yamaha RD400
1978 Honda Hawk CB400TII
1975 Yamaha RD125
1974 Yamaha DT250

The various year KZ650 bikes had different electrical systems, and the 1978 was not one of the best. Consequently, you may find that the Dyna ignition overtaxes that particular system. Ed

I've run Dyna S for several years and found that they tend to self-destruct with city commuting and low RPMS.
The main issue is a very long dwell with very low resistance coils.
While this may be perfect for drag racing and high RPM (>8k), it's a notable drain on the underpowered charging systems of the Z650 series.
The transistors cook under the points cover and will occasionally short, leading to a damaged coil.
The high current tends to oxidise the coil wiring, even with a wiredgeorge relay mod.
You can offset this with a 1R5 50W ballast (not perfect), the 5 ohm Dyna coils, or use a later model Spectre type transistorised ignition.

If you are comfortable with electronics, there are a few DIY options detailed here.

As Ed and Weezee said, the Dyna S is not always the perfect match for a 78/79 Kz650. Some of those bikes had slightly weaker charging systems which the Dyna S may overtax. Odds are that your bike would be ok with it, but of the many bikes using the Dyna S, when there is a problem, it seems it's more often a 78/79 Kz650.

If the charging system is in fact weak, the solution is usually to get a 3-phase stator and 3-phase reg/rec. Or go to a more efficient ignition (like a factory electronic ignition).

However, if your bike is having issues with ignition, as you may suspect, then you should probably do a few voltage tests first. If the bike is having problems powering the stock ignition, then it will have more problems powering the Dyna S. It could also be that your coils are going bad, in which case the Dyna S with new coils would fix the problem.

The Dyna S requires 3 ohm or higher coils. The points system originally had 4 ohm coils. The Dyna S works fine with points coils, as that is what it was designed to use, but it does heat the coils more, so you don't want to use marginal/old coils.

I don't know which kit you were thinking of getting so I don't know if it was a good deal or not. If it was my bike, and the coils are old/original, I'd be looking for some aftermarket 4 ohm coils (Dyna does not make 4 ohm coils for Kz's). Then I'd do some voltage tests to see if it's a wiring issue (voltage supplying the coils). If it runs good with the new coils, then I'd get the Dyna S, as it would work fine with the new 4 ohm coils.

The one upside to the Dyna S is that Dyna has been pretty good to its customers about replacing broken units, or at least selling replacement parts. For this reason, you may want to go through a retailer, just to have a receipt with a date.

What electronic ignition would be recommended for this bike, if not the Dyna S? Thanks for the reply’s.

One other thing to at least consider is keeping the points system. I've owned my 1977 KZ650-C1 for 41 years (since it was new). It still has the stock points system. In the more than 60,000 miles I have put on the bike I have found that the points need to be replaced about every 8,000 - 10,000 miles. Even then the bike runs fine, but the points do tend to become pitted over that many miles which slightly affects peak performance. The most important thing is to ensure the new set of points are correctly adjusted when they are installed. If you decide to install new points until you find an appropriate electronic ignition I can provide instructions describing how I adjust mine. Ed

LexPaul wrote: What electronic ignition would be recommended for this bike, if not the Dyna S? Thanks for the reply’s.

I always stick with the factory ignition. It has some advantages. Mainly it is much less wasteful on electricity. Also, unlike the Dyna S, when the crankshaft is not turning, it does not draw any current from the coils. This can save the coils in case you leave the ignition on while the motor is not running (if left for too long, they have been known to melt). You should be able to swap coils, igniter, pickups and rotor from a Kz750-four or a later Kz650. A 550's igniter and pickup plate will fit as well, but the advancer unit will be different. Sometimes it's hard to piece all of that together, and the coils could be old and suspect.

So really, if you must have an electronic ignition, the Dyna S is probably the easiest route. Make sure to keep an eye on the battery voltage. If it is sluggish to reach 14v, then you may have to look into a 3-phase reg/rec and stator. Or if you only do short trips, you can just remember to trickle charge the battery.

The first thing is probably to assess your 4 ohm points coils. If they are good, they can be used with the Dyna S. The Kawasaki factory electronic ignition will require 2.2 ohm to 3.0 ohm coils. If the coils are originals, then you may want to replace them regardless. If you get 3 ohm coils, you can use them with either type of electronic ignition. You can even use them with points for awhile, but they will deteriorate the points quickly.