sounds to me like your trying to start the right engine before the left has finished spooling.
keep an eye on ur engine rpm, when the rpm needle hits 70% your usually safe to start the right engine. Or just under the engine selector there's a green light marked "START VLV" it lights up when you start the engine or apu, if you flick this over before it goes out, then the other engine will start to crank. so either wait for the engine to fully spool up or wait for the light to go out before hitting the RH engine.