Did you try testing the ht leads by putting a plug in it and touching it against metal you should see it sparking a bright blue sparks do this one at a time leave the otheir plugs in the bike and extract them one at a time having the bike in nuetral push the start button if all spark a strong spark your ht leads are fine if your bike has coils this will show the problem or it could be a rectifier ,or your carbs need a good cleaning and might need to be balanced hope this helps