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cox 140 gas engine

Old 10-10-2010, 05:13 PM
Otter Guy
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Default cox 140 gas engine

just got an old cox gas engine. has a nice aluminum shroud but theres no recoil, or evidence of having had one. got it to fire rapping a rope around the flywheel, but the carberator is totally U/S. im thinking the new fangled ethenol mixed fuel might have eaten the diaphram or something, it was just a sludgey goo where it looks like a diaphram should be. anyone ever seen one of these things? know where parts might be available or an adaptable carb? if i get it running im thinking of building something for it, not sure what yet.
Old 10-10-2010, 05:39 PM
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Default RE: cox 140 gas engine

Hey Otter..
I have one of those which I converted to CDI. I have a pic posted in the New CDI forum. I had no luck with the grey plastic carb that it came with so I bolted on a Walbro carb to run it.. Seems to work great for me. The first one I had, I bolted onto a Bud Nosen Citabria and it flew so realistic I was impressed.

Old 10-10-2010, 06:34 PM
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Default RE: cox 140 gas engine

Look at the site above. It was known by Cox as the Beaver. It was sold as an RC engine by Hobby Lobby as the Rhino 1.4. The engine I have came to me used and with an adapter for using a glow plug in place of the spark plug. I plan to try it with a glow plug on gas/glow and maybe with an electronic CDI with gas. My carb diaphram is FUBAR and I plan to fit a walbro carb on it.

The attached images are some pics I have gathered.


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Old 01-09-2016, 10:54 PM
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Okay. Resurrecting an old thread. I got a Cox/Roper 140 engine on eBay and I want to convert it for airplane use. This thread is a little old and light on information. I was wondering if someone could help me with the conversion. I tried several searches, but my search-fu must be weak. The engine is 1.4, or 23cc. The output shaft is a keyed 1/2 inch shaft. I looked at the stickied how-to posts, but didn't find what I'm looking for. Specifically, how-to on prop shaft, possible carb replacement, ignition replacement, etc. Any help/suggestions would be appreciated.


Last edited by batjac1; 01-09-2016 at 11:03 PM.
Old 01-11-2016, 07:48 PM
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you can find more info look for the sears and old poulan chainsaws the older ones had roper engines the sears was blue magnesium cases
Old 01-12-2016, 07:01 AM
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Well, you will need to remove the flywheel and switch to electronic ignition instead. It is easy to get CDI ignition modules from many sources. The owners for some conversions made a flywall mounting plate to affix the engine with off the back where the flywheel used to be.

Then you need a prop hub to mount the propeller off the other end of the crankshaft. There is a slot for a woodruff key. The center bolt is used to help keep the hub on and you use four outer bolts to mount the propeller onto it.

The CDI ignition magnet goes into a hole you drill into the prop hub for that purpose. The hall effect sensor uses the magnet to fire the ignition coil.

What you do is use a lathe to make the prop hub. It is a relatively snug fit onto the crankshaft. But you don't bore the hole all the way through. You leave a shoulder or step so that the center bolt is used to keep it on tight with. The tricky part is cutting the woodruff key slot. You can't use a broach as the bored hole doesn't go all the way through. You need to take a lathe cutting tool and grind it to size. Then you lock the hub in place on the lathe and run the tool in and out shaving off slivers of metal until the groove is cut to about the right depth. I would go for a snug fit where you need to heat the hub up good so it expands and then slip it onto the crankshaft end (along with the woodruff key). Then put the center bolt in to help keep it on. Before you mount the prop hub, of course, you need to put in the four mounting screws for the propeller too.

Last edited by earlwb; 01-12-2016 at 07:11 AM. Reason: add more info
Old 01-12-2016, 07:46 AM
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Photo # 1, 5, and 6 look like they are gas / glow with a glow plug conversion adaptor. That would save the weight and complications of the CDI or magneto.
Old 07-20-2020, 01:29 PM
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What carb are you using gr8flyer55

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