Generator Rotors and Engine Swaps

On a number of occasions lately, I’ve tried to explain the “timing tab” on the charging system rotor. This tab is part of the ignition timing system. On the 1500A, B, C & D motorcycles, the tab combined with pulsing coils mounted on the left side engine cover send a signal to the Igniter which then sends a signal to the coils and the spark plugs. Starting with the E1 (1998) series of Classics, the ignition timing was determined by the tab/pulsing coils and a throttle position sensor mounted on the carburetor. Then, beginning with the E2 Classics and G1 Nomads, the tab became longer to allow for variable timing based on engine rpm and throttle position.


Now, understanding this is important when doing an engine swap. When putting a later model carb’ed motor into a 1500D, you must address this timing tab or your bike will not run properly. It will backfire and have no power. I learned this the hard way when I installed a 1500E2 charging system on my D1 motor. I ended up using my dremel tool to shorten the length of the tab as described below.

I used to think that this longer tab was in place on the 1500N Classic and 1500L Nomad Fuel Injected bikes, but recent research has caused me to question that. The same can be said for the 1600cc bikes.

I recently obtained a spare rotor for my 1600 Nomad and the tab appears to be about the same length as the one from my 1996 Classic. I no longer have that rotor to use as a comparison, so I’m kinda guessing here.

OK, nuts and bolts time. Looking at this first photo, you can see the raised tab as indicated by the arrow. This is a photo of my 1600 rotor. Also notice the location of the tab in relation to the keyway. This will be an important reference point.

When you do an engine swap, you should pull the rotor from the new motor and the old motor and compare the tabs. An easy way to verify the two are the same is place a protractor on the side of the rotor with the “0 Degree” mark aligned with the keyway and measure where the tab starts and stops in terms of angular degrees. If you are using the igniter for the old motor, you want to make sure this tab is the same on the new rotor.

I’m suspecting that rotors from FI models, both 1500 and 1600 are similar. Why not just measure the length of the tab with a ruler? Because the diameter of the rotor can be different. On a 1500A/B/C/D the rotor is about 5-3/4” in diameter. On a 1500E and this 1600A, the rotor is 6-1/4” in diameter. The radial length (angle from tab start to tab end) needs to be the same, though, due to the larger diameter of the newer rotors, the tab will be longer when measured with a ruler.

On some motors, swapping the rotors is the easy, safe way. On 1500A/B/C/D’s the rotor is smaller in diameter. Using one of these rotors in a newer motor will not work as the pulsing coils will not sense the tab and the spark plug coils will not fire. If you plan on using the older engine’s Igniter, you’ll have to grind the tab so it’s the same radial length of the old motor’s rotor.

I should point out that many 1500D Igniter were prone to failure and replacements can be hard to come by. It will cost you some extra money, but getting a 1999 and newer Igniter along with a Kawasaki Throttle Position sensor to add to your carb will be a more reliable system for the long run. The older harness will plug into the newer Igniter. The throttle position sensor has its own plug in.

I hope this helps provide some insight.

Also, here’s some blog posts from when I did the work on my D1:

http://www.bierkansbikes.blogspot.com/2006/04/latest-modification-dual-stator.html

http://www.bierkansbikes.blogspot.com/2006/05/eletric-system-upgrade-part-2.html

http://www.bierkansbikes.blogspot.com/2006/06/putting-it-all-back-together.html