A mate of my has a wr400 which is a pain to start when cold. It will fire on choke for a few seconds and then stop, and then fire it up again it will do the same thing. And by the third attempt it will run ok if your gentle with the throttle, if your not it just pops and stops any ideas?. As this only happens when cold ,the rest of the day it runs fine with no bogging or sputtering. Ive done a search and i cant find anything really usefull.