Reply To: GV650 FI 2002 – REGULATOR / RECTIFIER Instant overheat

[Zargoo]

Hey, thank you for the nice and detailed answer, so it took me some days but I was testing and this is my progress so far with the help of your recommendations.

At first I measured the phases like you suggested, which I did many times over the course of searching for the issue, and they always measured fine at around 0.26-0.28 at cold after sitting overnight and right after 5k rpm.

Now the stator basically always measured fine in terms of ohms. Now what I found is I hooked up the oscilloscope again and measured the phases phase to phase again, aka Pin 1-2, 2-3, 3-1 again, and also used the pick-up signal to get an RPM reading. And at 5k rpm I had 28V – 30V – 18V, which is very uneven; the drop to 18V is quite suspicious. So it seems it was like you said, an unbalanced load.

So with that info, I ordered a new stator and also a genuine Shindengen FH022AA.

Now after swapping the stator and the RR and also making an adapter with a 10A fuse, the problem was that the fuse always blew. At ignition on it was fine; at crank it blew. I then used a current clamp to test the amps on start and it was 15A, so I swapped to a 15A fuse and it now worked. Now from testing, the headlight takes 5A, the fuel pump at idle also 5A, and the RR seems to charge at 15A, and measuring at the battery positive wire, it receives 5A of charging current at 13V (the battery was a bit discharged already and was only at 12V).

Also, the main fuse on the bike is 30A, and yes it uses a Daewoo ECU, and it also still has the original Daewoo pump. And also yes, it is not using a Lithium battery; it’s a YTX14-BS gel battery.

Now at idle everything now seems fine; it no longer overheats the RR after 30 seconds of idle. Also, I tested with an external battery, connected the RR directly to a fully separate battery, and it charged at a better rate of 14V than what I saw on the bike at idle.

Though now I have quite a different problem that might be worse or better, not sure yet. Because the following is happening now: at idle the bike runs and seems to be able to run until there is no fuel. But when I rev the bike to 5k rpm, something weird now started happening. The first few times it is fine; the charging current goes up to 14V at high rpm then drops again. Stator phase to phase is around 35V – 40V; at idle it’s at 30V.

Now I am yet uncertain what the exact cause is, as I did not yet start to investigate, but it yet seems to happen randomly. I rev the bike, I can see battery voltage drop to 10,62V at high rpm with 12-15 amps pulling on the battery. Then after the revs and load, it goes back to 5A and 11V, which is way too low, and then the bike runs for 10-20 seconds and dies.

Now I did not yet test anything and will start probably tomorrow, but that is my first observation for now and might be wrong. I checked the RR 15A fuse and it was fine. One of my suspects is the ground strap from the battery negative, as this might cause high resistance under load and drop the voltage. Also, it could be the battery, as even if it did test on my tester at a low impedance of 12.62 mOhm, it could still be faulty. Also to note, I did connect the RR directly to the battery, not using the harness, and the same thing happens.

Also to note is that when I first got this bike, it was not starting at all and the issue was a cooked wire. I was testing each ECU wire and noticed some mismatches with the wiring diagram and then after opening the harness found 3-4 wires melted together. After fixing those, it ran, and I then had all the issues with the charging system. Now at least with the new stator and RR it seems fine, but still something might be off.

Also interesting is the tachometer, as it has an FI lamp which from reading the manual should turn on when there are issues with the FI system. From the manual:

“The injection signal is stopped, when the pick-up coil signal, roll over switch signal, NO.1 & NO.2 ignition signals,
NO.1 & NO.2 injector signals, fuel pump relay signal or ignition switch signal is not sent to the ECU.
In this case, “FI” letters is indicated in the LCD panel ① continuously. Motorcycle does not run.”

So I once disconnected the pick-up signal, but the FI lamp never turned on. Back then, I just thought it might be a defective lamp or tachometer, or it just needs the issue to happen while running for it to be memorized on the next start. (This was at the time when the bike did not turn on at all.)

Now I also tried the dealer mode switch and it also never worked or showed anything on the tacho display.

Also, on the wiring diagram I saw there is a CAN TOOL connector, and it looks like a K-line connection to the ECU. I also tested this with my motorcycle diag tool but also could not get any readings on any K-line protocol. And as this is not a Delphi ECU, which I know for certain works with my diag tool from other bikes via K-line, I just ignored this as I thought this might just be a different own protocol on the Daewoo ECU, or simply the Daewoo ECU might not have a real diag at all.

Also, one more weird thing when I started testing is the radiator fan turns on, but the tacho shows the water temp at nearly the lowest; from like 10 steps it has, it was at 2. And from other bikes as reference, usually the fan turns on at at least 5 or more. And also, one weird thing is the km on the tacho, because the bike should have around 2000 km, but the tacho just shows the maxed-out number possible of 999999 km.

Because of that, I am now slowly starting to think maybe it’s also an ECU issue, though it’s a bit unlikely, or so I think, because the ECU itself gives power to the fuel pump and injectors and the bike does run fine. If there were any major issue with the running itself, then maybe, and to be honest, I’d rather just have wrong things in the tacho than the bike run poorly or not at all and requiring a new ECU.

But just wanted to provide a bit more context about the bike and how it started, as this might help with the current issue I am seeing where the bike dies with a very low battery voltage after some revs, even though at idle it seems to charge, and on an external battery it charges even better, it seems. As I am also uncertain if the 15A fuse on the RR is really correct, or if that is the issue already and it should be less than 10 but is on this bike for some reason 15.

But already, thank you for the big help, as this is my first Hyosung bike and I’m really hoping to get it running, and sadly I don’t have any other Hyosung bike I could reference, as just having a second running GV650 FI would immensely speed up the diag.