Is the idle set to around 900rpms? It makes a big difference on starting. If the idle isn't high enough(850, to 900 rpms
) then the throttle plate isn't letting enough air in. These bikes will idle as far down as 600 rpms, when their warmed up, so even though it idles fine, make sure the idle is correct.
As mentioned, a couple of twist of the throttle, and full enricher before hitting the start button, and don't touch the throttle after, until your ready to ride off. When the bike starts, don't touch the throttle. Within 10 seconds or so, the idle will start to get lumpy. When that happens, ease the enricher in about 1/2, and leave it there(don't touch the throttle until your ready to ride off) until the bike has warmed up(you've ridden it a ways, depending on outside temps), and then push it all the way in.
^^This is proper starting. If this doesn't work, then the float has been bumped, and is to high now(good mileage would seem to argue against that, but)....or,....
If you can't engage the enricher at all, I'd look to see if you or somebody else, put a main
jet, in the starter jet hole, by accident. Wouldn't be the first time. Especially since the last guy had things bungled up. The stock starter jet, is a 56(I think),or it may not even have a hole.