when you try and start it and it doesnt start do you pull the plug and it looks like it all wet???
yah temp with make it harder to start, exspecially on something bigger than a 125,
is the choke circuit working, might be plugged up not letting enough fuel in, is the float set right, maybe getting to much fuel, air filter could be dirty, rider may not be used to the starteing procedure of the bike, kick from top dead center and go all the way through the stroke,
there are som many things it could be, since its an older bike, carb could be all gunked up, and jets and any and all passages should be cleaned out, you dont need new jets just run some realy fine wire throug them to clean them out, the cabe strands off a throttle cabe or something similar will work.
give me more info on the bike and ill try and help you more
My truck & A Cowboys Dream!! enough said