Your running the wheel too far back. You should run the wheel further forward to line up the....the ....OH I forget but in general the rear wheel should be further forward. Something to do with the position of the freewheel in relation to the position of the jockey wheel on the RD.
Some dropout adjuster screws would help, if the holes are not plugged.
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“One morning you wake up, the girl is gone, the bikes are gone, all that's left behind is a pair of old tires and a tube of tubular glue, all squeezed out"
Sugar "Kane" Kowalczyk