yzf-r125

hi i have a yzf-r125 yesterday i went out on my bike and everything was fine stopped off and my m8s house for a couple hours then went back to ride my bike but it wouldnt start. i tryied for a bout 10 mins then left it for a bit to settle but still without it starting then my battery went flat. so we started trying to bump start it and the first few goes nothing but then it did start but it only idled for about 2-3 seconds then dies and would start again for about 2-3 mins next time it started we tryed to give it some throttle but still it cut out as soon as we touched the throttle in the end we charged the battery up for about an hour to give it some life but still wouldnt fire once more we tryed to bump it and hey presto it started fine and i thought it was ok but the same thing happened tonight when i finished work. just to let you know last week we changed the engine as i blew the old one up but the old engine came from a good working bike that had only done about 800 miles. other that that the scorpian exhaust and the evotech tail tidy everythings standard. any ideas? thanks jamie

yeah on youtube the are a few exhausts on there but not sure which to choose did really like the weller racing pipe but not for 6 months. and i just bought some green angel eyes for it ill post some pics when i get them

hi i just ot my r125 still got a dt125r tho love the r125 but the sound is a real disapointment only bad thing about the bike cant wait until some nice tuning companys make a decent sounding exhaust for it. and a little more power would be nice .