sounds like a fuel blockage. its rather a coincidence that both atv's are doing the same..
perhaps you've used dirty petrol from the same can to fill them?..
question: is it the correct fuel for the vehicle? if not drain it out and put some good stuff in
I test fuel problems by spraying a bit of "Aerostart"( ether ) down the carby and kicking it over. Ether will start everytime if there's a spark.
If it starts on ether, it's likely the fuel ain't getting through. Clean filters, clean lines, clean tanks... hopefully don't have to strip the carbies and clean them as well
