Well Guys, after over thirty years in the bearing sales business, 27 with my own Company, I would wholeheartedly agree with Ian.
The benefits of running in oil far outreach the extra seal keeping out the crud. If there was so much contamination in the oil, the bearing would be the least of your worries.
Heat dissipation, less braking force from the grease, and far less friction from the oil lubricated unit would certainly extend the life of the bearing.
I would always take out the inner seal, but its your baby, your money and you pays the price, you makes the choice.
Good luck
Darren
I always think that if you leave both sealings in your gear box, the bearing over time will fill with oil. Especialy if the bike is on a side stand.
Once the bike is started, the oil cant't get out, putting the bearing under pressure. I think thats a risk, isn't it ?