Shifter incompatability?

Big_Paul Posts: 277
edited July 2014 in The workshop
Built a new bike, using a Sora 3503 front mech with Deore M590 mtb shifters, from day one the shift on the front has been very heavy, I read somewhere that the Sora road mechs have a different pull than an mtb one, the indexing is fine, it's just painfully heavy. Rear is fine.
Disc Trucker
Kona Ute
Rockrider 8.1
Evil Resident
Day 01 Disc
Viking Derwent Tandem
Planet X London Road