Back-up race bike build
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Greetings from NZ.
I’m new here and just having a beer and thought I’d spin a yarn about my project I’m currently working on.
I bought my first Hyosung (2014 GT250R) about a year ago to race in our Hyosung GT250 stock class. The owner threw in a carb’d “parts bike” with a blown motor to sweeten the deal. It literally came with parts all over the show – 3x forks, clutch cable, throttle cable, vent hoses – everything completely stripped away from the frame except the loom.
I’ve just finished my first ever season of racing on the EFI bike and have now started going through the parts and putting the carb’d bike together.
After emptying the boxes on the floor, I found I was missing a few things – exhaust headers, rear inlet manifold, rear brake mount plate and what seems to be a seized/rusted rear brake piston. The blown engine came with it, minus the smashed rear cylinder and head as well as the soon to discover rare as hens teeth….. rear inlet manifold! Not a wrecker in NZ had this, nor did Hyosung NZ/Korea or USA. Europe had one but after placing the order, 3 weeks later the order was cancelled as their inventory was incorrect. I finally convinced a fellow racer to sell me his spare. I have sinced sourced evrything I’m missing (I hope) and have started putting it all together.
The bike was set up as a race bike and was running fine before the engine blew 2 years ago.
I stripped the carbs completey down and cleaned them out for no reason other than they had been not been in use for 2 years, and I wanted to see how they worked. Down side to this was, when I was cleaing out crud with a pick, I touched the little brass hollow screw head and it literally fell off! I put a socket on the second one and started to apply pressure, and it too, fell off – be careful with these if you ever need to touch them. I also ripped a fuel hose between the float bowls – not a great start.
Parts sourced and carbs now back together. I put the engine and carbs into the frame. I found a good post in this forum on carb vent hoses which was extremely helpful along with fuel ‘pump’ and hoses (thank you). I had taken the battery from the efi bike and hooked it up to the carb’d bike and tried to start it but it failed to start. Problem seems to be no spark at either spark plug.
Thats where I’m up to for now. I’m guessing I’ll post in the Technical forum to problem solve this.
See the link below to the first round highlights put together by a chap at TT Kiwis – this is one day of racing (4x races). There are about 6x Kawasaki 400’s on the grid fighting for their own championship points, the rest of the field is about 35-40x Hyo GT250’s (all years).
Some pictures below of my project.
2nd primer paint job after 1x highside and 1x lowside on the efi bike 
Parts laid out to see whats missing 
Carbs stripped and cleaned 
Be carefull with this little guy -
Now i will get to follow this topic, great write ups!
Sourcing parts can be a head scratcher sometimes but glad you was able to do things locally first, so you’re on the road much sooner. Speaking of, hopefully the spark issue may be a minor thing but i trust that you are doing some electrical checks all over the bike to make sure nothing has gone amiss
That little arcon nut for the carb, trust me when i say i get more orders for that little nut than any other carb part for the bike. They are so fragile indeed.
Hell, i love how you neatly laid out all the parts for the build, i hope it wasn’t for a photo op 😉 , that’s very organized, some days my work shop is like that but when its super busy , things can be looking a little chaotic!
I remember many years ago when i first got in to Hyosungs , while i was busy scouring the earth for parts, i did come across an NZ FB page that did have the Carl Cox cup pics shared and some girl called Avalon seemed most prominent on a GD Hyosung, so that spiked my interest in GD bikes , however the UK rarely gets imports for the GD450 even! – So i ever only rode with 1 guy on GD250, what a quick light bike that was! – I still like the GT bikes for their chunkiness, i can’t help it! – So its nice know the Hyosung race scene is still going strong in your country, maybe Carl should make a UK one happen haha. I will be there all the time!
I am digressing , i’ll end to say i do like the grey bike due to its tail & solo seat style. I just need to add red lights and indicators , registration plate to make it street legal and i will be set!
Best of luck fixing the electrics!
// Meditation doesn't mean you have to sit still....
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Yea, the laid out parts turned into a photo op – my work benches where full of crap and the floor was the only empty space.
Avalon was before my time, but I too had noticed her. Not sure what she is racing now. There are only around 5-7 GD bikes in the field and I think it just comes down to cost – they are a little more.
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Little bit of progress.
I’ve carried out a couple other checks with the electrics and I think my coils are my problem. I tested the resistance on my magneto pick up coil and charging coil and they are both within spec (0.6 ohm and 109 ohm). I was also getting a small voltage through the coil primary wire when pressing the starter for a couple seconds, so I’m hoping that means my coil theory is right. I have ordered a pair of coils from a wrecker, so hopefully show up next week.
Also put my forks on and discovered why the bike came with 3x fork legs…… 1 is bent! If I can be bothered, I’ll have to get around to painting the leg bottoms both black.
While I’m waiting for the coils, next on the list is to look at the rear brake system.
Black fork, silver fork. 
Starting to resemble a bike. 
My process of elimination list. -
Best of luck with the coils, i do also have a suspicion that the harness should be in the list of investigation as per my previous comments. Neutral sensor works if it says “green” on the dash.
Mind you the harness itself has mystery sensors embedded in them (hyosung calls them diodes) and there is a strange ball diode near the front call , we call that the “igniter” , to do with the overal bike sparking system, so have something “MANNOL TAPE” to retape the whole harness properly if you ever check the diodes are okay. Your meter will probably have a DIODE test function on it for the mystery sensors embedded in the harness. Hyosung hasn’t told any one how to test them , other than replacing it or replace harness.
The flat rectangular sensor that’s near rear coil section also is Neutral and rear coil. Just a heads up.
// Meditation doesn't mean you have to sit still....
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I hope the harness isn’t the issue, that’ll mean more cold nights in the garage! Or a replacement harness from a wrecker, they’re about NZ$15 here (GBP $7). Nothing to say that it wouldn’t have issues either though – luck of the draw I guess.
Thanks for the heads up on the diodes, I’ll have to look into them to get a better understanding. I had an issue with a KTM 450 motard a couple years ago where I had issues with both the left and right LED indicators turning on at the same time whenever I used the indicator. I traced it back to the indicator lamp on the dash – the dash indicator lamp shared the common wire and the LED’s allowed the power to flow both ways causing them to both switch on. After a bit of research all I had to do was put a NZ$0.65 diode in the common line in the dash and it solved my problem – I saw it as type of 1-way valve.
Yep, the neutral sensor was confirmed early as it was showing on the screen and it would go ‘out’ when I put it in gear.
Are these the diodes wrapped up in the photos below? The front one is in a heatshrink cacoon and the rear one is a rectangular brick – is that right?
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As per photos , you are correct 🙂 Diodes / Mystery Sensors and the black ball thing is likely the “igniter” which is part of the sparking system too.
They have wrapped that so tight with only black wires out of it suggesting its not something that fails often , i hope not.
// Meditation doesn't mean you have to sit still....
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EFI GT250R and Carb GT250
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