Hi all, looking for some help please. Bike running and starting fine yesterday and became gradually more difficult to start. It would almost catch then bubble and fart or backfire.  Sometimes would start on full throttle. Spark looked a little weak but I was outside. Stripped the carb today, changed the plug started ok ish but better after being tipped on its side. Any ideas appreciated. 

Check all the grounds around the coil. Crappy mounting point for sure.

I’ve just checked the spark and it’s great, it sometimes starts and dies or backfires

If it starts easier when it’s been on it’s side then it sounds like a float bowl problem ,is it leaking petrol out of any of the over flow pipes when you turn the petrol tap on? take the carb apart again and check the pin is properly in place which the 2 floats pivot on , also check the jet under neath the floats is opening and closing properly when you lift the floats up by hand , sometimes it gets abit gungy in there and can cause the floats to stick open and make the bike run like a pig 

Did you clean the pilot with compressed air? 

All sorted thank you all. Full carb strip and clean.