Scotty,
To keep a gear engaged each gear that slides on the main shaft has a set of tiny springs (3 ?) with a single ball bearing on each that clicks into a matching recess, (detent). If you hav'nt already, download the manual offered in another thread and look in the gearbox section. Problems then possibly, springs are bound or stuffed and not pressing the little ball into the detent, the hole itself is worn not locating the ball properly, either way its gearbox apart if thats the case. Remember though its these springs and balls which fly in every direction when pulling a gearbox apart and you forget
, never to be seen again.....
Maybe the extra leverage from the quickshift combined with marginal springs has pushed it over the edge? however as its only first gear and you don't really need that one
hold it in manually with the gear change for now...