KF IV engine/wing upgrade?

[CaptBeach]

Can IV be upgraded to modern engines and the STI wing? If one were to find a KF IV for sale with a motor nearing MOH times...can it be upgraded to say a 915is or an XO-340?

[Dusty]

The 915 would be a tight if near impossible fit. The cg may become an issue also. A model 4 is generally lighter than the later series so as a bush plane has more than ample performance on a standard wing.

[CaptBeach]

Thank you. How about an engine upgrade to XO-340?

[beeryboats]

I'm tempted to toss my fresh Rotax and hang a Continental C75. If I only had the money. I hate two strokes. Starting to wish I never bought this plane.

[jrthomas]

Thank you. How about an engine upgrade to XO-340?
There's only one perfect engine match for the model 4. It's the 912. The model 4 was designed around the 912. It's the perfect size, weight and power. And it's as reliable as anything on planet earth. Model 4's perform great on 80 hp but if that's not enough for you and if you have the bucks, you can buy a built 912 with 150 plus hp (Edge) Or go with a big bore kit up to 120hp. Remember, you're working with a max gross weight of 1200 pounds. Hang a big engine on the front, then add weight to the tail to get the CG back in line,add full gas, have a seat and you've just exceeded max gross (solo). Someone on this sight recently said that Kitfox tested a model 4 with a 914 and determined the power was excessive. I have the 80hp on mine and I'm perfectly happy with the performance. The power is more than enough to get me out of any place that I'm good enough to get into. The 100hp ULs would be a rocket ship and I can't even imagine what a 120hp 912 would do to a model 4. The designers got it right. Match the engine weight to the airframe and you'll have a nice flying/performing airplane. A big heavy engine will make it a dog. (No offence to dogs). More and bigger ain't necessarily better.

[henrysamson]

I built a model IV with a 912ULS (100hp) tailwheel with all of the speedster mods except wheel pants. I can fly it with the long wing or the shorter speedster wing. I thought when I was building it that the longer wing would come in handy when I really needed the short field performance. To make a long story short, I have not flown it with the longer wing since phase one. The outboard wing sections are just gathering dust! I get plenty of performance with the shorter wings plus it's a bit faster and the stall speed is only a couple of MPH slower with the long wing.

Like the previous post stated, it IS like a rocket ship. Cool mornings, half full tanks and flying solo I become airborne in about three seconds in three point attitude and climb at 1700 fpm.

[jmodguy]

Thank you. How about an engine upgrade to XO-340?

The 340 is too heavy for a IV. Mine weighed in at 279.5 lbs. Useful load would drop to nothing. I will agree that the 912 is a great engine for the IV. My first Kitfox ride was in a IV with a 912ULS. Wow! It is an amazing performer!