Hello from Germany, work on it til it runs

[h00ty]

Bike Model = : Hyo GV125M E3 2007

Hi everyone,

I got my motorcycle license last year, and this 2007 Hyosung GV125 is my very first bike. It had only around 5,500 km (about 3,400 miles) on the clock when I bought it, but because it spent so much time sitting, I believe many of the components were still the original parts from 2007.

Not long after buying it, I started having some issues. The bike would stall after riding for more than about 30 minutes, and it would occasionally start hesitating and jerking while riding.

The first things I replaced were the ignition coils and the regulator/rectifier. I bought both from AliExpress. The ignition coils had different wiring than the original ones, so I had to rewire them, but that wasn’t a problem. The bike already ran a little better afterward.

Next, I replaced the spark plugs with iridium plugs from my local motorcycle shop and installed new spark plug caps that I bought from a member here on the forum. Again, the bike improved.

Interestingly, the original problem has now changed. It no longer stalls when the engine gets hot. Instead, after riding at around 100 km/h (60 mph) for a longer period, it starts to hesitate slightly and eventually loses power. The throttle test seems to indicate that it’s suffering from fuel starvation.

Because of that, I turned my attention to the fuel system. I cleaned the fuel tank twice because there was quite a bit of debris inside. I completely removed, disassembled, cleaned, and reassembled the fuel petcock. While I was waiting for the tank to be empty, I replaced the fuel filter and cleaned the fuel cap. I also replaced all the fuel hoses from the petcock to the fuel filter, from the filter to the fuel pump, and from the fuel pump to the carburetor. While I was at it, I replaced all the vacuum hoses going to the fuel pump to eliminate the possibility of vacuum leaks.

 

Unfortunately, the problem is still there. I’ve now ordered a replacement fuel pump, a new air filter, and a new chain and sprocket kit from members here on the forum. I’m hoping the fuel pump will solve the issue, as I suspect the original one is simply showing its age.

If anyone has experienced something similar or has any ideas about what else I should check, I’d really appreciate your advice.

I’m happy to be part of this forum, and thanks in advance for your help!

Please move if I targeted the wrong forum section.

[♠️ M77]

This sounds crazy but have you see the tutorials on the forum on how to carefully remove the airbox , then you can access the carbs to give them a much needed ultrasonic clean

Then check what jet sizes are still in the carb ?  Also we don’t know if the float needles are still working properly , these floats control how much fuel you can , if it gets too low before the pump can send more fuel, you will feel like its running on a dry tank then cuts out.  It wont start until you crank it multiple times , then it works (cranking was filling up the carbs again)

So maybe our next battle should be the carbs

Good job replacing everything else,  it just means you are serious about giving it more life , some people just abandon it which is a shame.   From what you said, it sounds like we should deal with the carbs and also double check the rubber pipes for any damage and replace O-RINGS which sit inside the rubber pipes

[h00ty]

I already inspected the carburetor once beforei got suspicious of the electric parts. The carburator looked clean. But I didn’t inspect the needles. That was before I found this forum.

I want to make sure that the fuel pump works correctly before I have to disassemble the carburator again. The last time it was pretty hard to fit it in again.

And yeah, since I found out about this forum I read a lot of posts here and yes I want to switch the main jets in the carburator but like I said, I wanted to make sure the pump works properly.

I make my analytics with ai and reading in this forum to get rid of all the failures that occurred. Works pretty good so far. When the new parts arrive I will make more photos of what I’ve done.

What rubber pipes and o rings do you mean?

And yeah I love this machine 😊

[Author]

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