• Topics: 38
  • Replies: 485
Nov 30, 2017
North UK

Hey @sebringmaster

Let’s try another method now,

  1. Go to halfords locally, grab a can called BRADEX EASY START
  2.  Lift up your fuel tank
  3. Spay lots & lots of bradex in to the air filter hole.
  4. Fire up the bike, hold the starter for 7 seconds max
  5.  WHILE the bike is “cranking” -> keep twisting the throttle multiple times…
  6. Once it fires ,  use full choke until it warms up for 10 mins.
    …..failing that….

Run to halfords or eurocarparts or MotoSave again,

  1. Grab a pair of NGK CR8E IX  (Iridium plugs)
  2. Connect 1 spark plug to the “IGNITION COIL HT LEAD” (HT Cap)
  3. Do not FIT spark plug inside engine.
  4.  Leave the plug exposed while connected to the WIRE HT LEAD
  5.  Switch on Dash.  Put bike in neutral.
  6.  Put the SPARK PLUG AGAINST the  “FRAME” or “ENGINE”  (Avoid PAINT)
    (Look for a metal frame part which is not painted)
  7.  Press the starter button   (keep the plug on frame)
  8.  If you see “SPARKING”   while it cranks ….
  9.  That means THAT COIL works.

Repeat this process with another COIL.

What we have done above ^ is checking if your ignition coils front & rear are actually sparking good.

if there is a weak spark.  It is probabaly the coils trying to give up the ghost or behaving erratic  (very very common on stock hyo coils)

OFF = 12.8v   / ON = 12.7v max  (it must NOT drop by 1.0 volts)

If a battery says 12.5 or less while on  (without cranking motor) = Investigate the battery , local bike shops can test your battery to see if the CELLS inside actually hold charge or quickly loose their 12v juice  (not matter how charged up it is, the cells must hold it)

Remember = GV125 , GT125 Comet & GTR use identical engine, identical coils….
So please have a read on these links where i gave more detailed response to the others,

  1.  https://hyoriders.club/forums/topic/hyosung-gt125r-starting-problems/
  2. https://hyoriders.club/forums/topic/2008-gv125c-headlight-running-issue/#post-1293
  3.  (Best one) = https://hyoriders.club/forums/topic/hiyosung-125cc-gv-running-slow-when-warm/


One thing to always remember =
High Revs / Hanging needle =  Air leak somewhere  / carburators probably messed with.

Boggyness / jerkyness / cuts =  Electrics & Fuel.

Common cuts are usually coils ,  fuel tap , clogged filter & rotted lines , carb has foreign gunk clogging its jets, side stand switch,  clutch lever switch

For more reading on carb 101 , check this out… (I talked about jet sizes & pilots)

[Tutorial] How to swap Carb Main Jets – Hyosung GV & GT 125/250

Report back and let me know how you get on!!

Last tip! – Remove the front spark plug -> spray lots of bradex INTO THE HOLE (in to engine)  – > reconnect the spark plug -> Fire up, and keep the revs up…. till it idles nicely to 1.7k rpm  (best spot)

Go to fuel station. Fill up 4 bars of fuel  (£4-5) , and buy REDEX 2 SHOTS (2 small bottles) -> Fill all of it in to the tank , so it mixes with fuel.

Ride your bike until the fuel level drops to 1 bar…. We have to see if redex can help attack all the gunk that travels on the lines, filter,  and also attack gunk in carbs, so that once it hits the piston, the get burnt off by the plugs.

Personally once a month, I use LiqyMoly (german)  , same as redex but for bikes with extra additives,  the principal is the same.  It means i have less maintenance work to do with carbs.


Good luck!

// Meditation doesn't mean you have to sit still....

Skip to toolbar