'03 TTR-225 hard starting

I've got an '03 TTR-225 that is ridden infrequently. In fact it probably
has less than 20 hours on it....looks showroom new. My problem is that it
is a bitch to start after it sits for a week or two. And it is electric
start only so it runs the battery down quickly. Usually the only way to get
it to start is to pull off the left side cover and spray starting fluid into
the intake. One thing I have noticed is that the phenomena is worsened when
the bike is leaning to the left on its kick stand. If I hold the bike
upright it usually starts much easier. Any ideas on what could be causing
this? I've had many, many Yamaha motorcycles and ATVs over the years and
NEVER have I had one act this way. My son has an '03 TTR-90 that will fire
up on the first or second kick every time, regardless of how long it sits.