I have a 1978 tomos a3 bullet and it doesnt want to start. At first I thought it might be the fuel filter getting clogged so I took it out and cleaned it out and it ran fine for a few seconds and then stalled. so I took it out again and did the same thing but it still wont start. so I checked the spark and it's fine. I also checked the air filter and it is fine to. the compression also sounds fine. every once in a while it will start, but only for a little while then it stalls and wont start. there where also three holes in the carb where the air filter goes, it was threaded so i thought maybe a screw is missing or something can anyone help?