? Engine swap Rotax 100 for 80

[shortfielder]

Mr. Evarts
Thankyou so much for taking the time to give me, and others, that great response.
I am still in the hunt for a plane. Sofar, I think the setup you have will do the best for what I want also. Higher alt., off strip flying(landing and t/o). I am looking for a -4 long wing Classic, hopefully with the 912s already in it. Just not sure it has enough room in it, so I am also considering the -5.
I will be going to Phx. in a couple weeks and get to see a variety of models. Hopefully after that, I will know exactly which model will work best for me.
Thanks again have a Merry Christmas and enjoy the holidays with your family, friends, and Kitfox
Gary

[shortfielder]

To Anyone

I think I have read where they have a kit to make 95hp out of the 80 hp engine. Would this be a better/more affordable option, or do you pay a penalty in reliabiliy/TBO? Trying to get more power out of an engine than it was specfiically designed for.

Thanks Gary

[Slyfox]

Thanks Les for the input. Yes everything you stated is true. I to have the vintage kitfox from 1995 with said motor. What I did was this. I had breakage of the motor mount with the 912ul engine, so It was a no brainer to purchase the newer engine mount for the 912uls. I had to change over the intakes and where the brain box sits, no big deal, I just copied what was set up on the old engine. I also put in new engine insolators and bolts. This allowed me to get 90percent of the engine change over done in a nice warm shop. You see I did this in the dead of winter, outside temps were around 10degrees. I originally used my old tank because the new one was not going to fit. I ended up cutting the tabs off the starter and than just beat in the firewall with a hammer and an object and that worked out just fine. Than the big day, I took my cherrypicker out to the hanger and in one day removed the engine and mount and put the new engine on. Only took a couple hours if that and that's with running into the pickup and warming up, got to remember it's 10degrees out. No heat in the hangar.

Now with that said there was also an issue with the water hoses, when you change around the brain box the water tank needs to change location also, so you will end up moving some hoses on top and changing at least one with regular heater hose, I don't remember anymore. The cover for the water pump is wrong, so at first I removed the one off the old engine, cleaned it up and installed it on the new motor. I originally put on the ultralight IVO prop and it worked, but I didn't like the fact that it cavitated on to much power. So I purchased the medium IVO which is a perfect match for the engine. I have an elevation of 2000ft and I get over 1500fpm on take off and in the winter can be as much as 2000fpm on take off. Cruise is around 120mph.

Now I had an opertunity to purchase the motor for about 1500less from an outfit in canada. Why didn't I do this? It's hard to trust across boarder businesses and I wanted things to work for the kitfox. Where did I purchase it, from John at Kitfox. Very wise move, because not only did I get the latest motor, I got the mods necessary to make the engine work. I got the engine mount, new and improved. I sent the cover for the water pump and John fixed that to work on the model 4 with a new gasket. I returned the new tank and John cut that down to fit. All this was free to me and they all fit great. The way I put the engine on, it was running in two days and flying on the third. What a joy. I had already purchased a new radiator, it was just sitting in my hangar. The new radiator was an aluminum one. So when I did get the water pump housing and things warmed up a bit. I emptied everything and put both the radiator and the water pump cover on.

A little suprise to me was that fact that the new engine comes with sensors that are one wire. The sensors on the old engine were two wire. What happened was all the sensors read to high. Now with my little wisdom I didn't want to trust the oil pressure sensor and moved the one from the old engine to the new, good thing, at least that one was right. The other sensors were wrong and to rectify, I had to move those over also. If I had a dynon, they would have been just fine, but since I had guages of a different type it didn't work out.

All in all I think things went just fine. Here is a list of some of things I had to do.

Replace the motor mount, I felt the tubing was just too thin, it wouldn't hold up, was nice for getting things ready to install.

Needed to get the water pump cover set up for the model4.

needed to modify the starter and firewall for clearance.

needed to move the intakes so the carbs set on the outside along with moving the water tank and hoses and the brain.

needed to send the tank to John for cutting down the size for clearance.

I installed filters behind the carbs.

I put straight hoses to the carbs from the fuel pump, haven't needed the return system, didn't have it before so I went with the simple.

I reinstalled the oil cooler I had

reinstalled the oil thermostate.

I really thought the kitfox was great with the 912ul, but after installing the 912uls, wow, what an airplane.

[Les Evarts]

Steve,

Ahh yes, I forgot about the issue with the water hoses. I should have made this #1 on my list of most likely issues to deal with in this conversion; it’s a given because of the engine mount. It’s also the easiest to fix. I solved it the same way you did, by changing the parts out of the old engine. If you can’t do that, you would need to buy a new elbow and replace/redirect these hose attach points. Or as you suggest, John at Kitfox provides excellent support on these type issues and its and the best place to go for information and support.

Interesting you mentioned the motor mount failure. This too happened to me and as part of my conversion, like you I ordered the new one from Kitfox. It’s improved as per the Skystar SB-54A. This is another missed detail on my account of issues related to this conversion. It should be item #2 (if not already done; actually, its mandatory as of April 2001, see SB-54A) on the list, so shift my 1-5 to 3-7 and add your observations to the top. However, when I did this, I did not re-order the arms that I mentioned in my earlier post (because they were thought to be the same); hence I had to modify them as per item # 5 in my earlier post. I’m comfortable, but watch this stuff like a hawk.

You’re close, if you ever drift east with the prevailing wind and get close to Polson… let me know, we’ll line up these Model IV’s and compare notes to see if those “speedster mods” count for much.

Les

[Slyfox]

Doesn't look like you are too far away, either you come over here or I'll try and make it your way. Heck with trying to compare on the ground, lets do it in the air.