My motor died mid-ride... need diagnosis.

Okay, so.... My bike was running fine, and then for three or four days straight, it would bog down randomly and slow to like 15mph or so (hard to tell, no speedo), and would randomly pick back up again. The problem got progressively worse, and last week I was riding it and it randomly died while I was riding it... I couldn't get it to start afterwards, no matter what. I checked, and I have no shorts anywhere. It did this once before, but I think the main thing was that I ran it out of gas on accident, and once the bowl in the carb filled, it ran that time.

The little nib inside the stock plug wire cap fell out like two weeks ago while riding, and I jury rigged it for like 4 miles of riding to keep it running till I could get it home, then I cut the plug lead off of a lawnmower and spliced it into my existing one. Could this have anything to do with it?

I'm getting fuel, so I'm leaning towards electrical.

my question is, could what I describe happening actually break anything? The plug-wire connection is solid, already checked that. I want to know if the plug coming off while it's running or modifying (read- jury rigging) the plug wire could actually cause any parts to fail.

Also- forgot to mention it, but the killswitch was already disconnected.

How often do the CDI and the magneto fail?

OK, I found a guide on motoredbikes.com for troubleshooting the electronics.

crackers said:

Here are the specifications for the mag and CDI. You'l need a multimeter(under $5.00 @ harbor freight)
To check the mag set mutimeter @ 200 ohm (scale with pic of the upside down horse shoe on multimeter) use either lead red or black it doesen't matter for this test and touch the black wire with one lead and the white wire with the other, your reading should be around 2 ohm. Next using your lead wires from multimeter check the blue wire to the white wire, should read around 300 to 400ohm's.
To check the CDI set the multimeter @ 200k same scale as above. POS. lead (red one) to blue wire neg. lead (black one) to black wire, should be no activity on multimeter (infinite) reading. Next POS lead on black wire and Neg. on blue wire should read about 130 to 150 k ohm's. Next POS. lead on Spark Plug wire and Neg. on blue, should read about 135 and 155 k ohm's. Next POS. lead on plug wire and Neg. on black wire. should read 2.5-2.7

Click to expand...

here are my results.

Magneto

1) should be around 2 Ohms, my result was 2.5 Ohms Good?
2) Should be 300-400 Ohms, I got infinite, and with the fluke on "automatic range" I got between 4.5 KOhms and .8 MOhms (I think this is the culprit)

CDI

1) Infinite reading. Good.
2) 130-150 KOhms specified, My reading was 306.3
3) 135-155 KOhms specified, My reading was 308.8
4) my reading was 2.5 K Ohms, so this is good.

My understanding from the results is that my magneto is bad, because from what I can tell, the resistance through the windings is WAY too high. What about the readings on my CDI? Are they OK, even though they seem to be high? Should I get a new CDI, too?

In other places on THIS site, I've seen the Ohms for the CDI to be listed as between 250-ish to 350-ish. In this case, wouldn't my CDI be fine?

Bikeguy Joe said:

Do you have no spark? Or did I miss something? Also, check to be sure your jet hasn't unscrewed and fallen into the float bowl.

Click to expand...

yup no spark. Water got in that damned case and bricked my magnet, from what I can tell. I think a shunt formed on the windings.

Ok, so, these are the following parts I ordered-

www.sickbikeparts.com- Magnecor plug wire, new NGK spark plug, and their hardware kit upgrade (needed all three, because I have the broken-rear-mount issue, and I don't like having a jury-rigged plug wire) By the way, Sick Bike Parts LLC - Performance parts for your motorized bicycle is AWESOME. I called and they answered on the first ring, and answered all my oob questions. I ordered at 1630 Friday and somehow they managed to get the parts here today, with standard-rate shipping. I just now got the shipping confirmation for my Dax order today, and I ordered from there first. (still pretty fast shipping, I think. My Amazon order from last Monday still isn't here yet.

www.thatsdax.com-a new set of grips (because I was already going to spend 9 bucks on shipping so I wanted my money's worth), a new magneto, and a rear mount clamp thingie (because mine fell off)

I just figured I'd update this thread one last time...

Got the rest of my parts today. Install was fairly straight forward. I was correct- it was in fact the magneto that bricked itself. After installing it and test-starting, I went ahead and threw in the new plug and plug wire... WOW. What a difference. I don't know if it was the wire, the plug, or both, but with the Magnecor plug wire and NGK BP6HS, idle was a LOT smoother, and the engine seemed more responsive throughout the RPM band. I went ahead and installed the upgraded hardware kit, except for the front engine mount, exhaust, and intake studs (because they seemed fine, and I'm lazy) with medium locktite. I discovered after removing the motor that the rear studs had broken off flush with the casing. 30 minutes later, I had them removed and the new ones installed and loctited thanks to my trusty extractor set and my 50-year-old bench vise. The motor is now reinstalled and lined up, and I took the chance to go ahead and remove some of the slack in my chain. I also used about half a tube of black RTV and a roll of electrical tape sealing up my clutch cover and magneto cover and magneto wires, so hopefully those areas are now waterproof. After it was all said and done, I installed my new grips from thatsdax.com, which was pretty straightforward, necessitating only the drilling of one hole in the handlebars so that the pin on the throttle assembly lined up properly.

My baby LIVES!

Now all I have to do is find my dremel so that I can port-match my new cylinder, exhaust, and IM that I ordered, then I have to find my soldering iron so that I can re-jet the new carb. Also, I ordered a slant-head. I'm hoping that with all the mods that I've listed, I'll gain some good oomph for the straights. It can't hurt, in any case... I'll have spare parts from the cylinder up now, in any case.

Any thoughts?