During the week I posted my woes on the Rotax Owners forums and messaged some contacts on the Zenith forums and most everyone pointed me at some Service Bulletins from Rotax that basically say the floats in the float valve often go bad. One bulletin says you need to check the operation of the floats every 25 hours until such time as they come up with a new design. So I decided I would give the float bowl a good clean and weigh the floats.
After cleaning the bowl I put the floats on a scale we had borrowed from a friend.
From the SB: if the two floats together weigh over 7 grams then they both need to be replaced. Well, there’s one problem for sure. It looks like my floats have absorbed fuel in the bowl and gotten two big to float properly (and thereby not shut the fuel valve off when full). It isn’t obvious to me how this has happened (one response on the forums is that it just does with some faulty floats) but they will need to be replaced.
Looking online I see that last year Rotax introduced a new design for the floats 861-188 which is supposed to not suffer from this problem. I haven’t yet seen any reports on how well they are doing. I’m not sure if they’ve solved the problem but at $150 for a pair they’ve certainly solved the problem of any extra weight in my wallet. Outrageous aviation markup.
They should be here before the weekend so fingers crossed I put them in, fire it up and everything is good to go.