Just purchased a Model IV (N149BT)

[RoyHelsing]

Well, a lot to learn here so I will be searching the Archives. After flying a Turbo Cirrus for about a decade and a few thousand dollars, I sold it with my company and decided to get back to the basics. Did the sale yesterday in WA but will not pick it up for a couple of weeks. It is currently in a tri-cycle gear configuration (UGH) but converting it back to conventional gear before I pick it up (and adding ADS-B out) before I pick it up. i am curious about a ton of stuff as a new owner, but for now just a question of what fuel those of you flying 958’s are using and why? Seems like with all the issues with ethanol, 100LL may now be the lesser evil?DA7426BD-E732-4DBF-8628-2DA0AB525945.jpgD048A7C5-E1DD-491E-BC2B-BA7854DD0F3C.jpgDA7426BD-E732-4DBF-8628-2DA0AB525945.jpgD048A7C5-E1DD-491E-BC2B-BA7854DD0F3C.jpg

[t j]

Roy, here's a link to a 1994 Kitfox factory promotion video. at 6:45 you will see your Kitfox and an interview with Ben Travis, the builder of your kitfox. He and and his wife flew it to Alaska and back. That's what encouraged me to build a Model 4 kitfox.

https://www.youtube.com/watch?v=KqDGMpmXm-4



Tom Jones

[RoyHelsing]

Thank you, Tom. The folks at Moses Lake where I purchased it all knew Ben who has no passed. There was only one owner between Ben and myself. He flew it one hour as a tail dragger, then converted it and flew it another 4 hours. The A & E friend of Ben’s did the conversion and will convert it back (I will help) to a tail dragger. For the past 20 years I have been flying C310, then two Cirrus - last 12 years a Turbo G3. seeking my business meant selling my Cirrus so after 7000 hours of primarily cross country flying it is back to basics. It has been 40 years since tail dragger flying - so I am looking forward to this. It looks like Ben did an excellent job building this plane, and an excellent mechanic/pilot named Derrin Jackson has done an excellent job making other modifications. Can’t wait to go up and get it, hopefully mid-June. Lot’s to learn here - but I am excited.

[t j]

If they are not already with the paperwork for your Kitfox you should order "Kitfox Pilots Guide", and "Pilots Operating Handbook Model 4"

Direct link to Kitfox parts catalog. Books are on page 7. https://kitfoxaircraft.com/parts/

[RoyHelsing]

Thank you, There is a POH, but no harm in ordering a new one. The Pilot’s Guide sounds useful also. One bit of confusion I am still hanging is what version of the Model IV I purchased. The POH shows a max weight of 1200 ibs. However, the A & E Imentioned before who was there when it was built says it is a “heavy hauler” and max weight is 1350 ibs. “Heavy Hauler” seems to be a name given to an AVID plane - so I am not sure what this plane actually is. It does have a cargo Pod that can hang below it - but I am not sure that is a differentiator. Perhaps one of those books will help.

[109JB]

Congratulations on getting a Kitfox.

To answer your question regarding fuel to use with the airplane, I am not sure what a 958 is but from your pictures it looks like your airplane has a 2-stroke. Probably a Rotax 582. If that is the case, you would be best running ethanol free mogas. Alternately, you could run 100LL with the Decalin fuel additive which scavenges the lead preventing lead buildup issues. I have had two Kitfoxes powered by the 582. On the first it had fiberglass wing tanks and I ran 100LL with Decalin. It ran just fine like that but I didn't have that one very long. Probably put about 50 hours or so on it is all. Currently I have a different 582 powered Kitfox but this one is a hybrid with a Kitfox 3 fuselage and kitfox 4 wings and mixer system. As such it has the 10 gallon plastic fuel tank between the instrument panel and firewall. Because of this I have been running premium auto gas with 10% ethanol because there isn't a gas station for about 40 miles from me that has ethanol free. It also has a 6 gallon fiberglass wing tank and that tank will only see ethanol free fuel, either 100LL + Decalin, or ethanol free mogas. It runs great. Rotax recommends auto fuel for these engines and they approve up to 10% ethanol. It is really the rest of the fuel system that dictates what you can put in them.

If the airplane has the fiberglass wing tanks, given the vintage of the airplane, it probably doesn't have the newer ethanol resistant fuel tanks, so stay away from anything that has ethanol.

If you are not familiar with operating 2-strokes, a tip is that the EGT gauge is your friend. 1200 is max EGT and you don't want to exceed this. Stock jetting isn't the greatest at the low end. Rotax says 55 idle jets but I currently have 40s in and it runs much better. Also the stock needle has a lean spot in the midrange, so I switched. I can get you the part number later. The jetting chart is a little rich at the top end but is safe for EGT so I run stock jets dependent on weather conditions. I also run a homebrew mixture control that I can use to lean the slightly rich condition a little. The "Hacman" mixture is essentially the same as I have.

Getting back to operation of the 2 stroke, here are some bullets

• After start idle about 2400-2500 until the water temp reaches a minimum of 140 deg F. DO NOT apply high power until it is at least 140. It should only take a few minutes, and if it takes a long time you should check to make sure a thermostat is installed in the engine. The first 582 Kitfox I had did not have a thermostat when I bought it and it was a pain until I discovered it and put one in.
• After warmup the engine should idle down to 2000 rpm or below without quitting. May be rough, but should not quit. If it doesn't smooth out until 2200 rpm or so that is ok. This is where the idle jet is too rich. With the stock 55, mine would not idle below 2000 and was rough til about 2300. with the 40s in it will idle smooth down to about 1800 and I can go even lower but don't need to.
• In flight, keep an eye on the EGT. I had a Westach dual EGT and it was way off. I wound up putting in an automotive dual digital EGT but I like it much better. Had to weld in some bungs for the EGT probes but it is better IMO. My egt runs around 1050-1100.in cruise.
• One area you need to watch the EGT in particular is powered descents. When the prop unloads under power the EGT goes up and depending on conditions can go over 1200. I still make powered descents but keep an eye on EGT and adjust accordingly. Another option is to "chop and drop" where you pull power off enough that there just isn't enough going on inside the engine to get too high on EGT.
• If EGT consistently runs high or low you can adjust some by adjusting prop pitch. More pitch lowers EGT while less pitch raises egt.

All this may sound complicated but it isn't really once you get used to how the 2-strokes operate. It is a matter of understanding the engine and how it needs to be operated.

[RoyHelsing]

Thanks, it was complicated but it also was what I was looking for (I do have the 582, my typo, sorry). The plastic fuel tank on my plane has been moved to behind the right seat - but I believe the main tanks (10 gallons each) are the original tanks so I guess it is 100LL with Decalin for me because there does not appear to be any ethanol free gas anywhere around here either (although I will keep looking). The rest of the tips and instructions I will keep in mind. I did see it run for a few minutes before I purchased and the EGT’s were moving and it was idling although in did not check the RPM. Again, thank you very much.

[t j]

Thank you, There is a POH, but no harm in ordering a new one. The Pilot’s Guide sounds useful also...

The Pilot's guide will have the max gross weight information...I think. I sold my Kitfox a few years ago and all the paper work went with it.

Kitfox history here
http://kitfox.lazair.com/skystar/Aircraft_History.htm

Your serial number is 1499. Numbers 1400 through 1722 are 1050 max gross weight. 1200 max gross weight serial numbers start at 1723.

[RoyHelsing]

Thanks, Tom. That explains why the POH with it says 1050. The A&E that has been involved with it insists it is 1320, which is not even consistent with the 1200 of the Classic IV - Guess I will need to check the logs and see if some modifications were made and if not - just assume 1050. I appreciate the answer.

[109JB]

Aerodynamically the 1050 has a smaller vertical tail than the 1200. On the 1200 the height of the vertical tail was increased 7 inches and the rudder chord increased 2 inches.

Structurally the following changes were made from 1050 to 1200:

• The wall thickness of the lower fuselage tube between the wing strut mounts was increased
• The wing strut tubes were increased from 7/8" 0.035 wall tube to 1" 0.049 wall tube