Put some upgraded coils and sprake plugs on my bike now goes 64
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Hey,
It looks like you have a standard exhaust on it too, i will assume the bike is very young,A. is it under 5,000 miles miles ? and do you have any proof history of these 2 critical jobs (as Korean’s mention it on service manual if the bike speed drops)
- Valve clearances done and shims changed ?
- Compression test ?
B. Also since you changed the coils and filter, your speed will drop also again if you;
- Changed the Jets yet ?
- Clean the carb with air compressor (must be done believe me) or ultrasonic bath.
If using a rattle can carb cleaner, you will probably go through 4 small cans.
C. Air System checks (because you changed the filter)
- Spray the carb manifolds to see if revs change (speed drops also if the orings under the manifolds are caked up or too old by years not miles)
- Spray under the air box holes where carbs sit on, if revs change, you have a leak.
D. Fuel System
– If it’s a 66 plate. Korea says change the stock lines and the filter after 4yrs (whatever miles she is on now) – Old rubber can rot inside, old fuel filter can cause weird issues, it’s mentioned in the service manual. – Change lines and use a giant fuel filter that’s trusted , not china things. Lest the carb gets clogged up and your fuel pump won’t push hard if you want to ride faster
– Open the fuel pump, clean it with carb cleaner only .Do not use compressed air, as it has spring loaded mechanism inside.
– Fuel Tap that’s directly under the tank —> It should work as normal. If using a big filter, when you stop going for a long ride, you will ALWAYS see half-full or 3/4 full filter means the tap is working. Emtpy filters after a ride always suggests starvation is likely.
– Use e5 fuel only. E10 will cause a lot of problems even as much as bog downs , eats up manifolds eventually, eats up rubber bits, extra ethanol in the e10 can be corrosive to metal parts etc… it’s just a devils juice. Stick with E5 and use WYNNS XTREME GOLD (this brand only) from halfords , pour all of it in a 3/4 full petrol so that it will soft-clean your whole fuel system (it will try!) -
Furthermore,
E. Electrical.
Clean the laser plugs hard. = Do A to D first above before going for a test run with clean spark plugs
– Then take them out.Take 6 pictures (threads of plug, and also the middle of plugs) – Then i will assess how your bike is burning fuel. I will know if it looks like either air or electric or fueling is a weak link.
I will also quote a picture for you from the service manual that mentions other reasons for a speed drop. Remember a brand new bike does 82-88 factory , i have various hyosungs so i tend to know how they are!
You got this!
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Hey,
The bike is VERY lean, almost dangrous to the piston rings (if piston rings start to wane – you compression drops bad and it will never be as fast as it used to be)Heat also makes the valves tighter clearance wise , so ofcourse that will mean you will need to do valve clearances much sooner than later.
Now then, let’s deal with the fuel situation….
– Do this mod below or let your mechanic do it[Tutorial] How to adjust Carb Slide Needle (Tuning) – Hyosung GV & GT 125/250
It must be done.The plugs have a sooty black ring, it suggests the carb does get some fuel to idle.
The white center is very white, i mean white! – that means its not getting enough fuel when you’re “riding – whatever mph on the street”.
What jets are in it ? You should have already fitted the jets i sent you 90 and 92.5
or 92.5 x2
or 92.5 and 95 (max)Also if you or anyone has ever touched the carb, please ensure the float height is 7mm (not less , not more)
If the float height is affected in anyway , it will affect “riding, idling, starting” .
Follow above early replies for intake air system as extra air leaks near the airbox or manifolds or manifold orings will overheat the bike a bit and lean out the plugs.
Your own air filter is fine , that’s why i did not mention it. It’s brand new.
See how you get on fella, keep us posted 🙂
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After doing tuned up bike runs fine gunna keep old coils on till my new caps come
The NGK caps came with the factory fitted HT wire so don’t remove it. Deal with removing the black wire from the actual coil instead
as for updated coils, if they spark blue/white , they work as they should. Yellow spark just means the electric system is weak.
Owning various hyos myself i know full well the new shape 125s are quite picky when it comes to weak electrics , very veru moody starters but otherwise if everything is cool , they work fine and just ride away!
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