Andair check valve

[HighWing]

I guess I'm with Dutch on this one to some degree. The return line is a late addition to the Rotax system. I wonder if the apparent problems attendant to it's being a recommended practice is Kitfox related or if it developed in another environment entirely. I doubt you will find this discussion in any of the old List or forum archives and with almost ten years in my old IV and lots of hours alongside other Kitfoxes and Rans with hundreds of flight of six or eight engine starts and shut downs on extended cross countrys without it ever being a discussion item during the hangar talk sessions, it makes me wonder. I don't have one on my current IV and until I hear of the exact reason I should relative to the Kitfox installation, I probably won't have one on my new IV either. It would sure help me understand this issue if someone could give me a real life Kitfox experience pointing to the risks of not having one or even the potential benefits of having one.

[Russell320]

I'm with Dutch and Lowell. When I purchased my model IV, it had a nagging hot start problem. The fuel lines were routed against the case, no fire sleeves, and no return line. I rerouted the fuel lines with fire sleeves and added a fuel return line to the wing tank (with the proper orifice). That solved all the hot start problems.

These engines, IMO, do not have vapor issues. When they are shut down, the heated fuel in the lines increase in pressure to overwhelm the float needle allowing fuel to be dumped into the carburetor, and the fun begins. I'll bet one of the biggest problems with starter and battery wear is hot starts.

Here in AZ, we try the hardest to keep our fuel cool.

Russ

[jrevens]

I tend to agree with the last 3 posts also. When I first heard of this return line deal, I believed it was to help with hot start problems, then read about the vapor issue. What Russ wrote is exactly what I had discussed with friends before that. When you shut down, & the fuel downstream of the fuel pump cannot flow backwards through the pump, that solid column of fuel can produce tremendous hydrostatic pressure with just a relatively small temperature rise. That section of line, sitting as it does on the top of the engine, certainly gets heat-soaked after shutdown & might easily overpower the float needle & possibly overfill the carbs. Result- hard start. Routing the line into a gascolator or teeing in anywhere upstream of the pump will definitely take care of that issue.
The few long-time Kitfox owners I know around here have never said anything about vapor lock problems, & don't have the line. Again - good installation practice & fire sleeve are probably most important. I'd like to know what exactly caused this to become an "issue" with Rotax. Is it just further a** cover to guard against some poor installations? It would be good to know.

[HighWing]

I guess what prompted my comment was a 1999 Service Letter SB-912-026UL which mandated the inspection and possible replacement of the Stator Assembly.

The only difference between old and new stator assemblies was the size of the Adel style clamps holding the wiring to the assembly before exiting to the ignition modules or the voltage regulator. It finally came out that the certified version in certain airplanes used for training were, as expected, only inspected and maintained during the periodic mandatory inspections. Since the oil was checked and replenished through a small door on the cowl by student pilots and instructors, the engine compartment was an oily mess at the the time of the inspections. Some A&Ps were hosing down the engine with some sort of solvent that softened the insulation on the wiring within the "undersized" Adel clamps and it resulted in some incidents of shorts there. Definitely not good, but on the other hand not a real hazard with a properly maintained engine.

I did the deed. Not a big project and parts were complimentary from Rotax with free loan of needed tools, but it did require removing the engine. Would I have done it if I had really known the reason behind the failures? Not sure I would have. Another thought on that, I would definitely have been convinced to do the swap if they had really done the right thing and replaced the wire in the stator assembly with an aircraft grade wire using Tefzel or similar insulation. Correct me if I am wrong, but I believe to this day they still use wire straight out of Pep Boys.

In searching for the above service letter number, I found a new one specifically addressed, I guess, to my friend Hal (and others) regarding his large bore kit. For sure, this one is a CYA letter and the customer should definitely beware, but...