No Spark- What is Most Likely to Be the Problem? Urban Express

Have a Honda Urban Express with no spark. Luckily I also have another Urban Express that is working so I can swap parts from the moped with good spark to the moped with no spark to check where the problem is. I've seen the main things to check by looking at the shop manual, but was wondering if anyone had an opinion on the order of "most likely to be the problem to least likely to be the problem." Is there a more logical order to what I should replace first, second, third, etc., till I find out what the problem is? What parts are most likely to go bad or need to be replaced when you are troubleshooting a no spark issue on a moped? Just want to start swapping the most likely parts first then go from there. Thanks so much (edited)

Re: No Spark- What is Most Likely to Be the Problem? Urban Express

Why not start where the problem is ? The spark plug ...

work back to the source of what is suppose to happen ... The magneto and it's integral parts .

Check one thing at a time . Plug . Cap . HT wire . HT coil ...

Insure all connections are shiny clean and scratch tight . That requires taking every connection apart , including every grounding point .

Can't just look at it and say you checked it . Gotta put your hands to work so you know for fact .

Re: No Spark- What is Most Likely to Be the Problem? Urban Express

Okay, thank you very much. Much appreciated! The only things I have done so far is I just put a brand new spark plug in it and I already started to swap out the kill switch because it actually felt a bit funky when I used the switch, like something isn't clicking right so I thought that may be the issue. But I will use your advice and check everything you mentioned. Will probably take quite a bit of time to get to the bottom of this but I really want to see this moped get spark. Thanks again!

Re: No Spark- What is Most Likely to Be the Problem? Urban Express

Cdi would be a good place to start also..

Re: No Spark- What is Most Likely to Be the Problem? Urban Express

Michael Branscombe /

trim 1/4 inch off each end of the plug wire and reattach.

you can also put a volt meter on the wire to the secondary coil from the ignition … it should give you some sort of reading and jump when you kick the motor over , this sort of basic test just tells you if your ignition is making electricity or not and sending it to the coil that powers the spark plug.

Re: No Spark- What is Most Likely to Be the Problem? Urban Express

Thank you for the advice, this is all helpful to me since I have no knowledge on anything with electrical stuff. I have an NU50M that is running so I have been using that to kind of take parts and test it on the NU50 that I have that doesn't have spark. I was kind of in a rush today and wanted to start testing some parts so I did a few minor things. This is what I've done so far:

1) Brand new spark plug and gapped it

2) Swapped in a tested working spark plug boot (just the boot, not the wire or anything else)

3) Swapped in the kill switch from the running NU50M to the "no spark" NU50. The running NU50M has an electric start so the kill switch wire bundle does have an additional wire in it since the "no spark" NU50 doesn't have electric start, but I don't think it matters since it appears the electric start wire is really not part of the whole kill switch wire bundle.

4) Swapped in an untested ignition switch from the running NU50M. Just realized that the running NU50M is hot wired and doesn't even need its ignition switch on to get spark. So the ignition switch may not be working so I may swap the NU50's original ignition switch back in

5) Cutt off 1/4 inch of plug wire to the spark plug so it has a good connection to the spark plug boot when reattached. Didn't cut off 1/4 inch from the other end yet since it seems hard to get space to get my hands up in that space to remove it.

Still no spark. So what do you guys think I should attempt next? I like the idea that Michael gave of using a volt meter to test the wire to the secondary coil from the ignition and try turning the motor over to see if electricity is even being sent to the coil that powers the spark plug. I would have done this already but not even sure how to do it 100% right, so I'll have to take some photos to make sure I'm doing it right and post them here.

Or do you think I should swap in the ignition coil from the running NU50M into the no spark NU50? Or should I swap in the CDI from the NU50M to the NU50?

Or do you guys think I should run some other tests of some sort to narrow down the area that is giving me trouble?

Thanks again, I'm honestly a bit overwhelmed with this stuff. I really don't have a clue what I'm doing

Re: No Spark- What is Most Likely to Be the Problem? Urban Express

The cdi would be my choice

Re: No Spark- What is Most Likely to Be the Problem? Urban Express

Okay thanks, I'll swap out the CDI unit right now. I believe it is right under the seat in the Urban Express, right?

Re: No Spark- What is Most Likely to Be the Problem? Urban Express

Okay, I swapped out the CDI too. Still no spark. You think I should swap out the ignition coil now?

Re: No Spark- What is Most Likely to Be the Problem? Urban Express

Captain Janeway /

I'm not sure how you got the ignition switch to match. The nu switch has 4 prongs, the NU50M has 6. Get a voltmeter and check continuity in all of this.

Re: No Spark- What is Most Likely to Be the Problem? Urban Express

Interesting, are you sure? If so, then something weird is going on. I currently have one NU50M and two NU50 mopeds. All of them have issues but one of the NU50 mopeds does run. All of my ignition switches have 6 prongs and their corresponding receptacles all have 6 spots for the prongs. In the photos below I've attached what they look like. Two of the ignition switches are on the white countertop in the photo, and the other one is still in the red headlight housing. One of the ignition switches on the white countertop seems to have been messed with but both were tested working just a minute ago on my other NU50 moped that does have spark. To my clueless eye, the shop manual doesn't show a difference between the NU50 and NU50M's ignition switch in their corresponding wiring diagrams. Maybe I'm missing something here (edited)

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Re: No Spark- What is Most Likely to Be the Problem? Urban Express

According to the parts fiche , all years/models of NU50 used the same switch .

LOCK SET

35010-GC1-670

ASSEMBLIES WHERE 35010-GC1-670 IS USED

1982 NU50 A - HEADLIGHT / HEADLIGHT CASE

1982 NU50 AA - HEADLIGHT / HEADLIGHT CASE

1982 NU50M A - HEADLIGHT / HEADLIGHT CASE

1982 NU50M AA - HEADLIGHT / HEADLIGHT CASE

1983 NU50 A - HEADLIGHT / HEADLIGHT CASE

1983 NU50 AA - HEADLIGHT / HEADLIGHT CASE

1983 NU50M A - HEADLIGHT / HEADLIGHT CASE

1983 NU50M AA - HEADLIGHT / HEADLIGHT CASE

https://www.partspitstop.com/oemparts/a/hon/506b930af870023420a1f267/headlight-headlight-case

Re: No Spark- What is Most Likely to Be the Problem? Urban Express

Ok perfect! Thank you for the clarification PD, now I have at least one less thing to worry about

Re: No Spark- What is Most Likely to Be the Problem? Urban Express

Jack Rutherford /

Check your battery connection. I believe You need that 4 prong plug to get spark.

Re: No Spark- What is Most Likely to Be the Problem? Urban Express

Captain Janeway /

I'll have to look again. One must be an aftermarket switch.

Re: No Spark- What is Most Likely to Be the Problem? Urban Express

Oh my gosh!! Jack, you are a frickin life saver! It was the battery connection!!! As I mentioned earlier, I have one NU50M and two NU50 mopeds. I never even had a battery connected at all since my NU50M gets spark without a battery connection so I assumed the NU50 was the same. Not to mention all those stories I hear of people blowing out bulbs running their Urban Express mopeds without batteries, so I assumed you just didn't need one for spark. On my NU50M I just have a bunch of wires hanging where the battery is supposed to go, and even without a battery that moped gets spark without a problem and runs and drives fine. I didn't know the NU50 needed a battery connection for spark. I just hooked up an old dead battery (probably 5 years old I think) from another NU50 that I have and the moped finally got spark! I can't believe that was the reason. The shop manual doesn't even mention anything about the battery connection when troubleshooting a no spark issue, which I find very odd. But you solved my problem. I totally owe you. I finally have spark!!! YES!!! Thank you!!!

Re: No Spark- What is Most Likely to Be the Problem? Urban Express

Jack Rutherford /

You owe me video footage of it running. It’s not the battery but the battery connection. (edited)

Re: No Spark- What is Most Likely to Be the Problem? Urban Express

Absolutely! When it's running I'll send you a video for sure. You saved me tons of hours of work! Thank you!

Re: No Spark- What is Most Likely to Be the Problem? Urban Express

I no the one I used to have wouldn’t have spark unless there was a battery in to complete the circuit.

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