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Post by SMALL CC TEK on Sept 9, 2019 23:02:42 GMT -5
Does it say kymco on the motor?
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Post by benhonda on Sept 10, 2019 11:32:46 GMT -5
yes
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Post by 3strokeengine on Sept 11, 2019 9:32:50 GMT -5
That metal piece is a resistor for the choke circuit on the carburetor. Removing it will make the choke turn off faster by letting the heater element heat up faster.
The CDI box is a new one for me but every DC CDI needs at least 4 wires:
1: 12 volt switched igniton power 2: ground 3: trigger (hall effect sensor near flywheel) 4: ignition coil positive
The 5th wire (black/white stripe) is just a kill switch that is grounded to shut the engine off. The DC CDI boxes dont need this persay because turning the key off will shut off 12 volt power to the CDI and turn the motor off.
If i had to guess thats what the "missing" wire is.
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Post by snaker on Sept 11, 2019 11:18:14 GMT -5
I have a 50cc Kymco with a DC cdi setup The bike I was told ran, suddenly stopped and was parked for 2 years. I threw on a spare, used DC box I had and with a shot of carb cleaner it fired up. Fast forward to me putting on a new carb, and the bike won't start. Every now and again, it will pop when I first try to start it and then nothing. Plug is wet, there is fuel, starter fluid doesnt help. Testing for spark shows none.
So I buy a new DC cdi box, but it doesn't fix the issue.
Then comes the part that has me really confused...I've had one other DC cdi moped but it still had 5 wires at the CDI box. This one only has 4. I can identify 3, a ground, wire to the coil, wire from the pulse pickup. The last I would assume comes from the key switch...it is black with a blue strip.
But how can a DC cdi box work without DC line to it? Most wiring diagrams I see online for DC cdi still have 5 wires. Do I have to find a special DC cdi for mine?
I don't see a model name on the bike, but it is a kymco from 2001.
Here is the layout at the CDI box
A lot of this makes no sense. You don't appear to have power at the CDI but you said it fired up. Small CC Tek verified that your wiring is wrong if you have the machine you think you do.
How sure are you of it being a DC ignition? 100%, 50% , someone told you?
Whats the chances that someone die a hatchet job electric swap out?
Power: DC comes from the control area, key switch, on/off, etc. AC comes straight off the stator, usually a single wire, blk/rd or rd/blk.
Time to physically chase the wires you have at the CDI, as in remove tape/insulation and be 100% sure of turns and any added wire slices.
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Post by snaker on Sept 11, 2019 11:47:35 GMT -5
This may be of help. The connector pin layout is at lower left.
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Post by benhonda on Sept 11, 2019 20:53:09 GMT -5
I'm positive that it is a DC system, only 2 wires come from the stator Also, the CDI box that came with the bike was even larger than the aftermarket DC boxes.
The only times it has fired is with starter fluid...and those times it would only do it once...spray again and kick or run the starter all you want, it wont fire again. Come back the next day and it may (or may not) fire with some starter fluid when you first try. So, it is almost like there might have been very weak spark, but maybe the plug gets wet and then can't fire again?
Anyway, at this point the bike is pretty torn down, and a rewire was going to happen as part of making it into a mini bike. So I plan to rewire the whole thing, including changing the wires in the CDI plug to match the diagrams. Maybe this bike had some weird CDI box that was setup different inside and didn't conform to what is common today? But either way, I know the box I have now should be wired as shown above. I've totally rewired a AC bike before, this one will just require a few extra wires. Hopefully the engine is good and strong and the work will be worth it.
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Post by benhonda on Sept 15, 2019 14:58:01 GMT -5
Today I wired up the pins on the cdi according to the pinout's shown, adding a second ground and a DC power. The black with blue strip must be a kill switch because once I removed it I got spark! Nice strong spark too.
However, when I put the spark plug wire on the plug and tried to start the bike it turn over slowly near TDC, in other words it slows right down, then speeds up, slows back down, speeds back up ect. It does not do this if I pull the plug wire off the plug. So it almost seems like spark is happening at the wrong time. The motor turns over fine with the spark plug in and making compression, but as soon as I put the plug wire back on it wont keep spinning at a constant speed. Not sure what would make spark happen early.
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Post by benhonda on Sept 15, 2019 19:27:48 GMT -5
i messed around with the bike some more...got it to start with much effort (using kick starter since electric start wouldn't spin fast enough) and while I had it running for a minute or so I am now fairly sure it has either bad rings or maybe a valve not fully sealing. It would only start with the throttle WOT and having primed the carb several times. I did get it to idle but it didn't sound great. And at WOT it blew some smoke. And going from idle to WOT the revs did not pick up very fast. I'd bet whichever it was (rings or valve seat) was fine when it was parked. I wish people realized how bad it is for small engines to sit unused for years!
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Post by hellish100 on Oct 11, 2022 7:24:50 GMT -5
Bringing this back from the dead. I am trying to revive a Kymco Sento 50 ( Four Stroke ), and the CDI and other wiring looks exactly as the OP describes. There are only four wires going to the CDI. The machine has only 50 miles on it and I imagine was either put away or it stopped running. Either way, I am running into a no-spark situation. If benhonda is still on this forum, did you remove the factory plug from where a 12v source should be and run a new wire to it? ( Number 6 on the diagram ). I'm going to give it a shot.
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Post by hellish100 on Oct 11, 2022 9:16:50 GMT -5
Self Answered:YES
Running 12v to the port on the CDI and grounding to the frame did the trick. I had spark and got it running. Then I stupidly touched wires and fried the CDI!
Time to order one up but at least I proved that it's a runner. This thread helped!
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Post by GrumpyUnk on Oct 13, 2022 14:34:05 GMT -5
I bet a plug nickel that the wiring for a Kymco will NOT match the wiring for a 139QMB even if both were equipped with at DC powered CDI. Reason to say that is that Kymco CDI on the retail market are about 6 times the price of a generic AC CDI, and multiples of a generaic DC CDI. IOW, they are wired differently. Using a generic will not generally work without doing some re-wiring. If the link works, check here: www.motorcycle-manual.com/app/download/11005021226/moto_schem_Kymco_Agility_50.gif?t=1611508744 I looked and there are 4 wires to the CDI. B/L L/Y G B/Y Trigger is L/Y, G gnd B/K is volts B/Y to the coil. tom
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