Just recently I have been filling my Aprilia RS50 with some different 2 stroke oil to my usual brand. Usually I have been using expensive stuff from halfords but they didn't have it in stock the last 2 times I have been. I did see some other oil in there by castrol and it said 2T oil and i wasn't sure if it meant 2 stroke. Maybe I lack common sense but the shop next door stocked some 2 stroke oil but it was really cheap so obviously it wasn't going to be as good but recently my bike has been cutting out when it gets under 4,000 revs. If your wondering how it even starts its because I have to bump start it and it used to have to get to 2,000 to start but it has to get to 4,000 now but if I let it drop below 4,000 it just cuts out and sometimes doesn't even start back up so I was just wondering if this could be the oil or is the any other possibilities why it is doing this?