If you've cleaned the carby out and sometimes it takes multiple attempts to get it to work properly, (I'm looking at an ultrasonic cleaner to do this)then that perished gasket will be the problem. You can make those gaskets out of cereal cardboard but a replacement gasket should not be too expensive. If you can't get the spare part easily a homemade cardboard one will at least be better than what you've got now.
