are you sure there was enough oil in the engine?
anyway, since very long time yamaha doesn't sell 34L oil pumps anymore.
the only oil pumps available are the 1VJ pump and the 3AJ pump.
the feed side rotor thickness and hence the hauling capacity has developed from 4 mm (34L) to 6 mm (1VJ) to 8 mm (3AJ).
scavenger side rotor thickness is always 18 mm.
every pump is coded with 5Y1 on the bottom and a) no code (34L) b) 1VJ c) 3AJ on top.
there are also three different shafts:
34L: one groove (for circlip)
1VJ: two grooves
3AJ: three grooves
34L shaft and 1VJ shaft have equal length, only the drive pin hole position is different (because different thickness of rotor). therefore both pumps use the same sprocket.
3AJ shaft is longer and therefore requires a different sprocket (with code 3AJ).
yamaha advises to use the 1VJ pump for the following models: 34L, 55W, 43F, 1VJ, 2KF, 2NF, 59X(TT600).
3AJ pump should be used in 3AJ, 3TB, 4PT, DJ02 (generally every xt600 model since 1989 (tenere) resp. 1990 and also the later tt600 models).
nevertheless it is possible to mount the 3AJ pump in a 34L engine.
i would use the 1VJ pump for a 34L.
beside the pump you need two new o-rings and a paper gasket (to be mount between pump and housing). if you choose the 3AJ pump you need also the 3AJ sprocket.
hope this helps,