What's the gravity? 1) Airlock Means Nothing at all, it's a valve, not a fermentation gauge. 2) Some krausens can linger long after fermentation is complete, Belgian Wit yeast is notorious for that, I've had it sit with a krausen for 3 weeks after the beer reached terminal gravity. 3) 8 Days is hardly any time, if you had a 3 day lag in your yeast like may folks do the beer's really only been fermenting for 5 days...hardly anything. 4) Like Monkey said, ignore your kit instrcutions and leave you beer in primary for a month, and you'll be really happy with the results, or if you secondary, take a gravity on day 12 and again at day 14 and if it's remained the same, then rack it to secondary.
But having a karausen at 8 days is not uncommon.