The front bearings do leak from time to time, but they also get blamed for a lot of bad running that actually comes down to incorrect tuning

If the bearing is seeping a little after a run (especially if you are running rich) it's probably ok. If the front of the motor is covered in oil and dirt as well as the underside, then you may have a leak.

A leaking front bearing won't make your engine sound blubbery, it will make it sound really lean - because it is. Air leaking in through the bearing makes your mixture lean, and your motor run hot.
Normally this is signified by a fast pulsing, high revving combination when you come to an idle (machine gunning it's called).

Rule of thumb would be:
If the motor is at idle and then starts to pulse up in revs quite high and erratic - you have an air leak (or you are way too lean somewhere).

If the motor comes in reving high and then drops suddenly after 10 seconds or so, you are too rich on the bottom end and your idle gap is too wide.
This normally results in your top end being very lean too (in order for the motor to run like this). The motor will run ok, but at WOT you will be too lean, resulting in blown plugs and maybe engine damage if you are running really hard.