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    Re: 4A032 Military Gas Engine (12-15 HP) for off-road buggie?
    #11
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    Every time you reply I find something else to worry about..lol The engine mounting design seems like it's gonna need some beefing up. And maybe I'm being too cautious, but I'm still worried about the directional force that's going to be applied by the clutch. The shaft attachment seems pretty stout, but I'm still thinking it was designed just to spin something, not to have something pulling it sideways.

    Imagine the engine sitting there, and then imagine something snatching that shaft sideways. Imagine the thing snatching it has enough force to move 2 guys and a buggy at 40 mph.
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    Re: 4A032 Military Gas Engine (12-15 HP) for off-road buggie?
    #12
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    With all that being said, I would probably still give it a shot..lol Unless I could trade that engine for something better. The thing I like about it, it's a 524cc 4 cylinder, it probably has a ton of torque. And I agree with you, the 6hp rating seems low. I would imagine that thing would make 6hp at an idle..lol
    Last edited by LIDUNO; 03-22-2019 at 04:12 PM.
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    Re: 4A032 Military Gas Engine (12-15 HP) for off-road buggie?
    #13
    Millenium Member plkracer's Avatar
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    We had a 10kW version of nearly the same motor, used for farm duty. Came off a 400hz military genset. Need to be careful about overheating them, they would drop valve seats when the aluminum head expanded past the design limits.

    They are built just like a little lycoming, and they are a non interference engine. They dont run so well off three cylinders, haha
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    Re: 4A032 Military Gas Engine (12-15 HP) for off-road buggie?
    #14
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    Quote Originally Posted by plkracer View Post
    We had a 10kW version of nearly the same motor, used for farm duty. Came off a 400hz military genset. Need to be careful about overheating them, they would drop valve seats when the aluminum head expanded past the design limits.

    They are built just like a little lycoming, and they are a non interference engine. They dont run so well off three cylinders, haha
    Well that does it for me then, I officially change my vote.lol I would try to sell it and get something better suited for the job.
    If the cooling system is designed to keep it cool running just above idle for hours at a time, I doubt it would do well climbing a sandy hill or drudging through the mud.
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    Re: 4A032 Military Gas Engine (12-15 HP) for off-road buggie?
    #15
    Millenium Member plkracer's Avatar
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    We have no clue how hot it got, just started missing on one cylinder, but there was grass buildup inside the motor and on the fine cylinder fins.

    If you can monitor the temp like an airplane engine, you'll be fine.
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    Re: 4A032 Military Gas Engine (12-15 HP) for off-road buggie?
    #16
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    Ok the grass details would have been good to mention.lol I'm such a flip flopper.
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    Re: 4A032 Military Gas Engine (12-15 HP) for off-road buggie?
    #17
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    Funny crowd here ...

    These things were made to run at 3600 rpm for ... well, forever while driving a generator (with variable loading). That's why the gov't rates them at 6HP. These have been deliberately under-carbed (gotta be a real term, right?) and boring out the carburetor has noticeably increased the tested HP. A little head grinding has also bumped the CR to 8-1 or 8.5-1 by boosting the pressure 15-20 psi-ish. With minimal work these put out 12-15 HP.

    All that said, I'd never heard any stories of them used in off road vehicles. They have been used in ultra-light planes (not very successfully), lots of Cub Cadet and similar tractors, small air-boats, generators, and numerous other configurations. I've heard that they were used in go karts, but never heard from anyone that had actually done so.

    Just got a starter and a couple of alternate carburetors, so I'll see what I can do to fire one of these up again. Oh ... did I mention that the design was old enough that it was before ethanol gas. The carburetor float (foam) actually swells up and jams due to the ethanol. I have another carb on the way with what I hope is a suitable replacement brass float to try; I'll bore out the existing carb if the float works. If that does not work, I have an alternate carb that will work once I make an interface plate.
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    Re: 4A032 Military Gas Engine (12-15 HP) for off-road buggie?
    #18
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    Considering the relatively low rpm of that engine, I wonder if a carb off a 250 motorcycle would be close to what you need? Plenty of 250 ninja's out there. I know your engine is over 500cc's, but a 500cc motorcycle redlines at probably double what that engine redlines at. I would think a carb off a 500 would be way too big? I guess comparing carb bore size would be a good start.
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    Re: 4A032 Military Gas Engine (12-15 HP) for off-road buggie?
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    The current carb is 1/2" and they have been bored out successfully to 9/16" and 5/8". At 9/16", no further mod is needed. If bored to 5/8", I may also have to drill out the metering hole that the main mixture needle seatsinto by a small amount. The max carb bore size I've heard of is 3/4", but that is borderline for this engine. Again, with the stock carb, I have to change out the float to a brass float to 'fix' the ethanol gas issue. I don't really want to have to stock non-ethanol gas just for this project ... but I could. I do have an alternate carb that has been used but I don't have a lot of performance data from that. Since this is a 4-cylinder horizontally opposed, only one cylinder if firing at a time, so a smaller carb is appropriate.
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    Re: 4A032 Military Gas Engine (12-15 HP) for off-road buggie?
    #20
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    It's like a half scale vw engine.lol
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