I have a 2002 919 that I purchased about a year ago with 30K miles and unknown maintenance history. It started running rough last week, and got progressively worse, so I replaced the plugs (NGK) this weekend. Ran beautifully (night and day difference) yesterday, but started stumbling on the way in to work this morning. It stumbles at low RPMs and then clears up as the revs increase. I imagine it'll start stumbling all the time (like last week). I definitely smell unburned gas in the exhaust as well.
So, I'm looking for suggestions from you knowledgeable ones. I'm wondering if the plug(s) are somehow getting fouled - as opposed to there being a lack of spark. Should I invest in an HF noid light to check for spark? Pull the plugs and inspect (I have no experience evaluating them)? Other ideas?
BTW - I did purchase the factory plug remover, and I gotta say, between it, and my wife's midget-sized hands, getting the plugs out was a breeze!