When my Hyosung Grand Prix 125 has been lying a day or 2 without use it wont start using the electric start button unless i open and close the throttle a few times b4 i try to start it...if i leave the bike without use for a couple weeks then the button wont work what so ever (not even a noise and when i kick start it the engine will cut out if i try to open the throttle to soon. Please help I have no knowledge of engines what so ever

Allan brown, February 2010

Carb
also check the carb needle hasnt jumped. There are 2 positions. The wrong 1 will only let throttle rev engine a bit before engine cuts out. Could be dirt in carb as well? Mine had dirt, exhaust was smoky, carb dirt cleared and so did smoke.
Elec start switch is a crap design, had mine apart, cleaned it, then it started working - only to prove i had a battery which spun the starter a tiny bit b4 giving up!

steve, October 2011

My Hyper came with a Rob Hunter 50amph cold crank battery, mines dead. They are rubbish. Ppl on forums say avoid them. Charged with Oximiser 600 for many hours, no go. Dynavolt 80amph cc at 32quid incl. p+p seems good. Top ones, 100amph cc, are 50+ quid, but good in cold winters. Im getting Dynavolt as i live near the sea - a little less cold!

steve, October 2011

The reason it starts easier with a couple of twists of the throttle is because it has an accelerator pump that works off a plastic cam off the throttle cable wheel on the side of the carb,the accelerator pump basically is a rod that has a plunger on the end of it and that gets forced into a small well in the float bowl and forces a jet of fuel up into the venturi of the carb through a small jet therefore giving it a good shot of fuel which is what they like when they are cold,if its easier to start like this then it may be that the choke flap on the carb isnt seating up right in the venturi and not causing a vaccum in the venturi to draw fuel up the main jet,these are bascially a copy of a honda cg 125 carburettor.

adam bike doctor, February 2010

Battery!!
Is it after a coulpe of days the engine turns but slowly? After two weeks nothing? I would strongly suspect your battery needs replacing. When you start bike do lights get brighter at front when you rev it. If they do this is good, if not BAD!! Post back when you fitted a new battery

bb, February 2010