First, any help is greatly appreciated.

I bought a 2006 Honda Ruckus that had several issues, but I did it as a project and have enjoyed it so far. Trust me, this Ruckus was a mess, but I like a challenge!

So, here is what happens! I turn the key on, push in the front brake lever, turn the kill switch off, hit the start button, and the motor sounds like it has a dead battery and wants to crank. If fact, it will actually crank about a half a turn. Usually, it will hit the compression stroke and it is like it does not have the strength to push past it. You can kick start the bike and it fires up with no issues. I can use the kick starter with my hand and it will start right up on the first or second kick. So, here is what I have done to the scooter...

1. Rebuilt the motor with new crankcases (muffler mount was broken), piston, rings, etc. It has great compression and again starts very easy using the kick starter.
2. Purchased a new battery. I also keep it on a tender so it is at peak performance.
3. I purchased a used wire harness and still have the old one, but it was cut in some areas. I have replaced relays from both wire harnesses as they both had all the relays. Both wire harnesses do the exact same thing,
4. Valves were adjusted to spec and again it runs great using the kick starter, but will not turn over using the electric starter.
5. Alternator was replaced as it was damaged when I bought the scooter. I really thought this was the issue, but upon replacement it did the exact same thing.
6. Checked all ground wires for continuity and everything is good.

Here is what I do not understand...

1. I don't understand how the scooter reverses polarity and cranks the motor. I am used to a standard starting motor so the theory bewilders me on how it works.
2. I have a factory manual and it says nothing for diagnosing the starter / alternator.
3. The lights will not turn on immediately with the key.

Here are few questions...

1. Since the alternator / starter is not the issue, could it be the magneto? I am not used to these going faulty, but I guess it could happen. Again, the manual has replacement procedure, but not magneto diagnosis.
2. Could this be an ECM problem? According to the wiring diagram every wire from the fuse box goes through the ECM. I am sure it could impact whether the starter works, but I would not think it would act like a weak starter.

I really don't like just replacing parts just to replace parts. So again, any help would be greatly appreciated.

 

I did find the issue with my Honda Ruckus. I also want to reiterate that my Honda Ruckus was a total mess when I bought it. There was all kinds of hacks being done to this bike. It was a lot of work, but before I go any further I want to give the solution. If you want to read about how diagnosed it than you can read the brief summary of what I did to fix the problem.

Solution: Faulty ECM and the ECM was replaced

So, how did I come to figure it out? Well, it was the process of elimination followed by an educational guess. I started with the Honda manual which helps you diagnose starting issues. I personally don't like to replace parts just to replace parts. So, I ran every test the manual told me to test. This included testing the battery, fuses, grounds at different points, voltage at different points, continuity at different points, relays, switches, and ohms / resistance on different components. I did everything the manual stated to do and more. At the end of the day everything came back good according to what Honda's manual stated. By the way, if you want to know everything I tested I can make a list.

So, I started thinking, Honda does not tell you how to test the ECM. Don't get me wrong, they state how to test some continuity and ground points to the ECM, but the not the ECM itself. I also concluded that Honda's wiring diagram shows that the starting function goes through the ECM. How this works Honda does not state. Also, even if you wanted to figure it out, the ECM is a sealed unit. You might be able to take it apart, but I thought I would most likely damage the unit in doing this as it would have to be cut open. In the end, I found an ECM on the Facebook Market for $65.00. So, I took the chance and ordered it thinking I don't know what else it could be because everything else on the scooter was tested and approved.

I received the ECM and the scooter started right up. I started the scooter about 15 times throughout my day! By the way, I did not start the scooter 15 times in a row. I would start it a few times, come back a while later, start it up a few times and so on. As a note of caution, I would highly suggest you not start your scooter 15 times in a row or use your starter for long periods of time as this can make electronics overheat and become faulty. I personally believe, from the condition of the scooter, that they could not get the scooter started and damaged the ECM in the scooter by trying to start it continuously.

So, you asked if I ever figured it out. Well, since the ECM was not diagnosable and since everything else checked out to factory specifications my only option was for an ECM swap.

My educational guess worked out and I was glad to see that the scooter started after multiple attempts.

Let me know if you have any questions and thanks again!