Motorcycle Repair: Tranny leaking 1340 evo, vent hose, hypoid gear

Question
My friends 1340 evo didn't leak tranny fluid untill he over filled it . Started to leak a week later. He drained it down to the proper level but  is still leaking. If the seal is damaged, can he use a thicker ger oil to slow the leak down? How about a possible vent problem? Thahks, Geno

Answer
He can use an 80/90 or 80/140 hypoid gear oil.  But he should drain it completely and then refill it with only 20 ounces.  Make sure it's a leak and not just coming down the back of the inner primary from the vent hose.  With the tranny dipstick out, blow some air into the vent hose and make sure you hear it coming out the filler opening.  Yes a clogged vent hose could cause the Mainshaft seal to leak.