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Thread: Kitfox IV 582 vs. 912(80hp) only

  1. #1
    motortommy's Avatar
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    Nov 2016
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    Default Kitfox IV 582 vs. 912(80hp) only

    I know that this topic has been discussed several times, but anyway I would like to ask for some real life experiences. There should be folks who meanwhile have experience with both 2 and 4 stroke powerplants…
    Due to microlight regulation I`m interested mainly in comparison of 65(582) vs. 80 hp (912). So no focus on 912uls, zipper, edge,… options
    Is the swap worth the effort? Why/why not?
    Aside from short following pro and con list, how did your Kitfox IV changed? What real life numbers did you gain?

    con

    • cost (engine, mount, prop, accessories,…)
    • additional weight
    • no ideal installation with early mount (oiltank, carb position, …)
    • approval procedure needed
    • no quick and easy swap (cowling, cooling System, avionics,… are affected)

    pro

    • improved reliability
    • simplified operation procedures
    • better resale value of the plane
    • increased performance (cruise/climb)

    Thanks for any insights!
    Marc
    rebuilding IV-1200
    `Kitfox fifty`

  2. #2

    Join Date
    Dec 2009
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    Lawrenceville, GA
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    169

    Default Re: Kitfox IV 582 vs. 912(80hp) only

    The 582 needs to be topped and the rings cleaned every 150 hours. Otherwise the rings can stick and pistons gall in the cylinders. The symptom is a loss of power and/or it quitting under full throttle. Like when you are just climbing out over the trees.

    So if you stay right on top of the maintenance it can be pretty reliable. But that mode of total loss of power is why 2-cycles get a bad rep.

    I have over 200 hours behind a 582 in a KF3. But I don't want another one.

    I have an 80hp 912 in a 601HDS. It is no cheaper than a 582 to maintain if you do it yourself. But the engine is not likely to just quit.
    Building a KF IV Classic

  3. #3
    Senior Member Dusty's Avatar
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    Dec 2012
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    Christchurch, New Zealand
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    Default Re: Kitfox IV 582 vs. 912(80hp) only

    I fly both , The 912 is my favorite due to a higher cruise speed and better distance between stops.
    The 582 doesn't worry me on reliability or cost to run. A top end rebuild at around 600 hrs for an oil injected engine isn't expensive compared to maintainance on older 912 engines.
    If your "mission" isn't x country, a 582 is great, but needs a bit of understanding from the operator.

    The idea of repowering our very tidy 582 model 4 has come up plenty of times but can't be justified in our case. This may change with the demise of new 582's as the perception of parts supply may have an influence on future resale value.

  4. #4
    motortommy's Avatar
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    Default Re: Kitfox IV 582 vs. 912(80hp) only

    Thanks for your helpful comments, which meet broad approval (among same question I asked elsewhere).
    As my mission after restauration will be first to learn and extend tailwheel skills, I decided to stay on the 2smoke road firstly...one will see what comes later!
    Marc
    rebuilding IV-1200
    `Kitfox fifty`

  5. #5

    Join Date
    Dec 2009
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    Lawrenceville, GA
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    169

    Default Re: Kitfox IV 582 vs. 912(80hp) only

    I would highly recommend that the engine be checked out. The top end is not hard to do. If nothing else take off the exhaust manifold and look at the cross hatch pattern in the cylinder. Looks good or are there scratches? Much better to pull the cylinders and inspect. You can scrape a lot of carbon out of the piston ring grooves for what a set of pistons and cylinder work will cost you.

    If the rings stick what will happen is the increased blow-by will heat up the piston and it will gall against the cylinder wall. Once there is any aluminum on the wall it is all down hill. The engine will lose power at full throttle. Later it will seem to be fine again. It isn't. The power loss will come back and the engine will stop. And run again after it has cooled some. It will need new pistons and the cylinders honed out to the next size.

    Do you have a grey-head or blue head engine? If it is a grey head then take off one of the carbs and look in the intake. Are the big ends of the connecting rods (you can see the oiling holes) kind of brown and a cast surface or are they machined smooth and shiny? The newer crankshafts have larger bearings and the big ends of the connecting rods are larger. To make them fit into the case the rods ends are machined for clearance. I would not fly on the older style. I replaced mine; there aren't many good places to set a plane down around here.

    Another tip. The carbs come stock with a #55 idle jet. Have since day one. The engine runs way too rich at idle. The symptom is the engine loading up and quitting. Say like at the end of a long final approach. Also will load up and foul the plugs on long taxi. I would up with #45 jets. Also when to Iridium tip fine wire plugs. Cured the problem.

    Quote Originally Posted by motortommy View Post
    Thanks for your helpful comments, which meet broad approval (among same question I asked elsewhere).
    As my mission after restauration will be first to learn and extend tailwheel skills, I decided to stay on the 2smoke road firstly...one will see what comes later!
    Building a KF IV Classic

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