pit bike no spark?

im not getting a spark to the plug on my 125cc pitbike ive completely swapped everything e.g. plug, ht lead, ignition coil, wiring loom, cdi unit and the stator plate and it did start but the died about 20 mins later and now im back to square one with no spark. the bike is getting fuel and has compression but im stumped with the electrics. any help would be great thanks.