Author Topic: Seeking advice; frayed wire, Spark Plug, Funny Multimeter Readings on new part  (Read 1127 times)

Dianawatk

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Edited to add new info:

Hey guys,

I bought my SYM RV250 two years ago and have put 7k miles on it with commuting, back roads, etc. Works beautifully, love it to pieces, starts right up in 20* weather, etc. I rode it literally every day with maybe a day or two gap every few weeks. At most it was sitting for two weeks one winter, but I was still starting it three times a week during that gap.

I recently relocated cross-country and had the bike hauled out by a bike shipper; it was secured with ratchet straps with no issues, but still by the time it arrived, the wire harness' wire from the ignition coil to the CDI box / Transistor ignition has a frayed cover right before the CDI plug. We think it might be from rubbing against the square box on frame it had been looped through. Anyway, we didn't realize this when the bike arrived so I started it, it started right up, rode around town, worked great, but then as soon as I went on the freeway it died and wouldn't start again. Eight hours in a shop and $500 later, after extensive testing of the fuel and air systems, compression, cleaning carb, replacement of the spark plug, they discover the frayed wire cover.

I couldn't afford them to keep testing the bike, so I took it home to continue testing on my own (since now I had a lead, the service manual, and a shiny new multimeter!). Where the wire had frayed it had arced into the frame and melted the fuse to the starter relay. Melted the fuse holder, even. So I ordered up new parts for that and tested the CDI box (since shop had suspected it). CDI showed some interesting results. At first glance it appeared circuits were blown on the ignition coil and reading poorly all over the place. But editing post for clarity, now that I have the new box, I'm getting the same results as the tests on the old one. Please see my next post in this thread; I could use some help verifying whether it's the box, the book, or the tool that are incorrect!

First steps: Replace CDI box and starter relay when funds allowed (had to wait two months), and while waiting for new parts, I tested spark plug. Spark plug fired erratically, isn't just a "timing is off-cycle" issue but is completely random, maybe 2-3 times per crank of the starter.

Today, 4 mo. later: Installed new CDI box and starter relay, still no dice on starting bike. Didn't have spark plug socket on hand to test firing sequence again and doublecheck shop gapped correctly. Will do Wednesday when parts arrive. Tested ignition coil and pulse generator, found resistance 20x too high on ignition coil, 5x too low on pulse generator.

SYM uses CR8E spark plug correct? I found one place in the manual that calls for CR7HSA instead, but I'm afraid of having the piston slam into that longer plug if I tried it.

Any other advice for this issue?
« Last Edit: March 16, 2016, 11:36:51 AM by Dianawatk »

sunfish

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I suspect that the fraying of the ignition wire took place over a long period of time and has nothing to do with shipping. What could cause the fraying? Incorrect routing of wiring or a missing cable tie. Other suspects would be parts that dampen the vibration of the motor being worn or broken.
$500 and your scoot still not working! That is crazy. What you describe of the wiring is all visual was the mechanic blind.
Electrical is always the first and then fuel on an engine that is not firing.
Glad your scoot is out of that shop.

Sunfish

Dianawatk

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I'm glad it's out of the shop, too. The attitude the shop techs gave me when I walked in was enough that I should have just said, "eff you guys, I'm outta here" before even thinking of giving them my business. Should have told the tow company that we were going cross town to go to the other shop instead!!

I obviously have no idea how long the wire cover fraying took, but it appeared to have rubbed open against the square hole on the frame that's located nearby. It's on the approach to the CDI / Transistor Ignition, right before the connector plug. I need to look at the wire closer to make sure it itself isn't damaged, just the cover. I recovered it with a really good automotive electrical tape and disconnected battery before testing other components.

MORE IMPORTANTLY THE NEW CDI IS GIVING SAME READINGS AS THE OLD ONE. Key observation: Along the ignition coil circuit, the resistance readings for the battery, plus coil + and plus coil - are significantly less than they should be, on both axes of the chart. Everywhere else in the chart, measurements either mirror each other, or appear to be flipped + / - from what the chart says they should be. I have marked up a chart in Excel with my readings; green measurements are ones that check out OK (and all of these check out OK both ways), yellow are incorrect for the chart's recommended configuration but appear to be OK flipped + / -, and red are incorrect for both configurations. If that makes any sense.

So what I'm trying to do is eliminate variables to figure out whether it's my multimeter, the parts, or the book that's incorrect. If the book has the + and - swapped in the chart, IE where it says to use a negative lead on the ignition coil and a positive lead on the plus coil +, does it actually mean to use positive lead on ignition coil and negative lead on the plus coil +?

I was wondering if anyone can confirm these resistance measurements on the Transistor Ignition, checking the one they have in their bike? This would be HUGE for me. Since my new box is showing the same results as the old one, I'm wondering if the chart in the book is incorrect aka I wasted $200 for false info. Or am about to waste $200 I don't need to on another box. It's actually really easy to get to, take out the luggage box and it's halfway down the side of the bike on the right. A grey box tucked by several white connectors. To test it, disconnect it from the bike and hold the leads to the pins on the CDI box's plug.

Readings comparison chart in the service manual is in section 17-9, pg 200.

« Last Edit: March 16, 2016, 10:00:53 AM by Dianawatk »

sunfish

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I had a look at the manual reference, Page 200, but my scoot is still buried in winter storage so it is not easily accessible to test the transistor ignition. With ignition voltage shorting out was there any circuits that blew a fuse.   
I am impressed with the manual but there are translation problems.

Sunfish

Dianawatk

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I'm really impressed with the manual too, it's helped me a lot with this process. Very well illustrated, but some quirks here and there. I wouldn't -think- the chart would be reversed, I'm just really suspicious of getting these flipped readings from both the old and new part. So maybe the new part is "bad" too, or maybe my tool is bad. I have to eliminate all three potential sources of error, right?

None of the fuses blew, which is the crazy thing. Unless the shop replaced them and just didn't say anything! But looking at the wiring diagram, there's no fuses between the CDI box and the parts that plug into it. So it has a direct "fry-line" if anything goes wrong with the ignition or charging system :/

sunfish

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I was wondering about your meter also and the meter leads in the correct location. Also the battery in your multi meter.
It makes it harder when you have to recheck all the areas that the shop worked on.
Page 11,12,13, in the manual is about correct routing, bundling  and connectors.

Sunfish
« Last Edit: March 17, 2016, 06:26:43 PM by sunfish »

Dianawatk

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I definitely triple checked the leads and multimeter setup while using it. I most definitely had the black lead in the ground port and the red lead in the resistance testing port, and was using black on the - items and red on the + items. I also changed the battery partway through testing to rule that out as a factor. The unit itself could be weird. A friend is bringing over his multimeter to rule that factor out this weekend. I just want to cross-confirm if someone else's functional CDI / Transistor Ignition is giving the same readings as mine!

Dianawatk

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So, pretty please, can someone multimeter test their CDI box? I still have several hundred dollars at stake on whether it is my CDI or multimeter or the manual that is incorrect...

Dianawatk

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Alright, I'm done with the bike. Since I didn't get anyone's help with testing this, I wasn't willing to dump another $500+ into the bike shooting in the dark because I have nothing to compare to. It was getting fuel, air, and spark, so the only possible things remaining were electrical problems (which is consistent with the problems the bike had). But since no one was willing.able to help me get data on what their CDI box, their ignition coil, their starter relay exhibit on a healthy, running bike, I have absolutely zero chance of fixing this bike without replacing everything in it.

So this bike is now for sale after having sat for a year in storage with fuel stabil in it. I feel let down that I got no help with this, but I can understand it, too. No one wants to take a risk by taking things apart, no one has the time to spare to take something apart and take measurements for someone anonymous on the internet. But I still can't help but be soured over losing over $1000 in this vehicle trying to fix it, and knowing that it will sell for junk price as a result of getting no help.
« Last Edit: May 28, 2017, 05:28:34 PM by Dianawatk »

sunfish

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This forum is not very populated so you might get a better response on a general scooter forum where there might be lots of tech people. I was part of another brand forum and it was very active. Try a local area small engine guys power sport people they love these issues as they get there kicks from solving the problems.
Let me know if you still have the bike and I will get you your readings.

Sunfish