Area-51

If fuel related, 3000rpm and upward is the main jet circuit of the bing64 carbi. Check for incorrectly positioned tab or ruptured diaphragm or asymetric needle position height between carbis. (The diaphragms would be my first and easiest go to if everything outside looks correct). Check for a broken throttle arm or choke spring. If electrical, check the resistor plug connectors for correct resistance and ignition leads for arcing through insulation to earth at the inlet manifolds or cylinder heads. Verify plug gaps are set correct. Try opening throttle slowly and see if issue is still apparent; better or worse

I forgot to add "all" early pioneering flights were performed by Aunty Jack while listening to a fading and stretched portable Realistic cassette player tape playing Skyhooks album Living In The 70's.

Didn't the whole ultralight experimental aviation scene start in a garage with somebody strapping on a severely unpredictable McCollach rip start edge trimmer motor to a loin cloth spread out over a collection of rudimentary positioned hand selected portions of bamboo and choosing a patch of arbitrarily suitable ground upon which to end the short flight upon? 🤔🤷🏼‍♂️

The constant speed auto function is only functional while in Auto mode Hold selected between 5700max and 4000min on a 9XX motor.Pg47 POH. Auto Hold will return to last Hold speed setting until power off reset to Cruise at next power on. Manual adjust of Auto Hold speed is only affected via manual pitch adjust switch while both Auto and Hold are selected simultaneously. Section 9.2 Indications - LED signal colours and interpretations. Pg48/49 Section 9.3.8 Loss of Speed Signal - Failure of controller to drive pitch control. No LED fault indication at AC200. Pg 52 ANNEX B AC200 Controller, Sensor Brush Cable Pin Outs - Pin #1 Speed Signal Input, magnetic sensor. Orange/White. Pg70 Check you speed sensor circuit for loose or dirty connection. Airmaster & VP Props.pdf

The Carnival used a HondaV6, so did the MG ZT and Rover; all suffered the same issues of engine failure. At the time Kia had a national recall on 12.5 thousand replacement engines; MG/Rover national recall on inlet manifold assembly replacement due to coolant containment issues leading to engine failure. Many leading OEM auto brands manufacture in china. Many leading OEM electronics brands manufacture in china. Many components used in both industries are manufactured in china. Cirrus Aircraft, owned and manufactured by china... Boeing, Airbus, manufacture in china. Rotax, BMW, Can-am, manufacture in china. Mitsubishi, manufacture in china. Daimler Benz, manufacture in china. Ford, manufacture in china. Toyota, manufacture in china. Chrysler Stellantis, manufacture in china. PSA Citroen, manufacture in china. Harley Davidson, manufacture in china. Textron Cessna, joint venture manufacture in china. Let's give it a chance to prove itself and see if they are as good as the Rotax units being manufacture in the Rotax factory across the road from ZonZen's facility 😃👍

https://hildstrom.com/projects/2010/01/seafoam/index.html Make your own using diesel naptha and isopropyl...

Yep they are great. Just don't hang around it while its on unless you want to destroy your hearing. Tried jewellers solution at 80c. It cleans steel as new, and starts to dull alloy with more than 30min; and really darkens it if you leave stuff in for 12 or so hours. Have been using dish soap but will still dull the alloy. Tried coca cola without success... straight water or a thin oil works well.

The pistons/barrels were not removed; just a decoke sufficient enough on this occasion. Wouldn't do a piston crown polish insitu; too much grit going into the ring lands.

Yes, sugar soap is alkaline, sodium carbonate. It rips the carbon deposits off pretty quick. Pulled the test piston out of the acid bucket this morning. It did not clean off the carbon as well as the sugar soap, and did not dull the metal. Below are the test pieces. Right to left, acid 24hr, sugar soap 1hr, sugar soap 2hr. And a couple of pics showing colouration between 24hr acid and 2hr sugar soap.

Today has been a day of discovery and success while cleaning piston crowns on the 914. After reading MSDS sheets on various you-beaut metal cleaning products off I went to the magic shed cupboard. Pistons from the scrap 912 80hp were used to test some science. One was thrown in a bucket of Selleys sugar soap (oven cleaner), the other in a bucket of nanoic acid (herbicide). After 15 minutes the sugar soap had softened the varnish which could be wiped off with a rag. After 30 minutes more varnish came off with a tooth brush; and after an hour most all varnish was vanquished, and the metal was just beginning to dull a bit. After two hours the piston was stripped fairly clean and the metal had not dulled that much in total. The second piston is still sitting in the nanoic acid at the end of the day without much change at all. Then it was time to clean piston crowns. First a plastic scraper was tried and was all but useless at scraping off carbon. Then a piece of ebony was used, and was all but useless. Then a brass brush was tried which left scratch marks. Then a piece of 1.75mm aluminium sheet was tried. It worked great and left no scratch marks! Then a piece of broken piston skirt was tried and it worked even better, and left no scratch marks because it was the same hardness and material as the piston crown... After nearly 50years I just discovered this today; amazing... With all the wonder of discovery the piston crowns on the 914 all got cleaned as well as they could in the afternoon by first scraping the carbon off with the bit of skirt followed by a 15 minute soak of sugar soap and a flush out with carbi clean and Rostoff, followed by roll over until no more gunk flowed out of the ring lands, then a finishing off of engine oil. The carbon on the top of the bores came off easy after a scrape with the piece of skirt and some light wiping with grey scotch brite soaked in sugar soap. Ready for reassembly...

Thanks, will do some research on that one... I think we are done here on this. thanks for everyone's input; some useful applied knowledge to refer to...

The turbo unit is in as new condition and free of compressor binding... If I knew these engines as well as I know others I would now use them without concern. But I don't have enough time on these things to know their practical limitations. Will still put set of standard valves in to tick the box; about $550 a valve. The engine is being built for reliability and distance work. Old ones can get polished and put into a lesser 80hp scavenger rebuild test pig unit.

After realising yesterday the valve head crazing was deposition, out of interest today I took to some old skills and decided to see if the deposition could be removed.

Rotax have been using sodium valves since 2018 in all their turbocharged engines, the 914, 915, and 916 all use the same part number. Besides an AD requiring replacement on one manufactured batch I have not seen any reports regarding either valve or valve guide failure with their sodium valves; and there are sure to be TBO'd engines running on condition by now in the field. The factory change to sodium was due to more extreme combustion environment in the turbo charged engines, i.e. heat affected deterioration. A 914 with an intercooler might negate this however the 915 and 916 probably not.

The valve stem is magnetic. The valve head is not magnetic.

Got the Nikon out tonight for a closer look at the rocket science; definitely corrosion right across the board... so no thermal shock as thought...image of outer valve head surface thought to be crazed but it does appear to be raised rather than pitted in this area; something bonded, something eroded... It's all just electrical plasmodium in the end!

I'm going to have to correct you on this. Contemporary high performance valves do come in a few different alloys these days along with coatings to mitigate a variety of combustion ed related badness... Maybe some water went back up the exhaust when the AC went into a ditch and caused thermal shock of the valve face (crazing) 🤷🏽‍♂️; which is puzzling to me.

Corrosion from acid is definitely plausible; there is no head gasket on the 9XX engines or water jacket in the cylinders. Other than a crack in the head itself, that leaves atmospheric vapour/humidity as the source of moisture to create sulphuric acid, or previous owner running an ethanol fuel. I found only one other similar question from 2013 regarding this valve head pitting on a 9XX; which received no responses. The engine had only 120hrs on it with a single exhaust valve displaying corrosion pitting and degradation of the face. Perhaps a valve coating issue at production? Have ordered two new standard valves. It will be good to see this engine go back together. Glad it got stripped down for inspection.

From experience another aspect of engines running water injection is the combustion chambers are clean and free of carbon deposits upon removal of the cylinder head. Maybe rust from sitting idle for extended period that burns off leaving an indentation as the hours go on?

Cheaper than a destroyed engine. Seats are good 👍

Thanks, all other aspects are within specification and condition. Will put a new set of exhaust valves in for insurance.

Thanks for the technical information there. I did not factor in the water aspect regarding pitting. Would this not display across all four cylinders though? The deposits do not scrape off; at least not with light pressure. They are resembling crows foot aspects which I would associate with thermal shock. The more I get into this engine the less I am confident it has only run for the 147hrs logged. The valve throats are consistent with normal oil ingestion from the turbo shaft seals to induction side; nothing too extreme but not what would be expected at 150hrs TT. And then there is the lifter face condition previously found to consider as well. But the exhaust system appearance is consistent with 150hrs usage. Maybe some rascal got to it and swapped out a couple of the heads at some stage; who knows. At least its getting a thorough scrutiny and attention before spinning up again.

Interested on what people may think of these two exhaust valve images? Is this possibly lead fusion from running avgas? Combustion chambers and piston crowns all present well.

Failure is not the end result; its just the pathway. Started about 25 years ago with a program called Vellum, on an old macintosh classic, and a tutorial book drawing a 2D square. The shapes progressively became more frustratingly complex. After a month the square became a 3D cube. After a year an engineering professor let me use their lab after hours to learn Catia and model an airframe. Have not stopped since. Probably have more time than a senior qantas check captain and now design complex without any limitations other than time... Modern software makes the game very accessible and intuitive now days. Players still need to put in at least 50-100hrs to start jogging a little. After about six years you might play a little Bach or Dire Straights... try SketchUp or Fusion and just do the tutorials over and over until you start making your own shapes.

After several iterations and failures the 3D printed 9XX valve compressor gizmo works great 👍