4C engine install on J-3
 

I have a Saito .72 4-cycle that I am ready to install onto a C.G. J-3 cub. Does anyone have any tips how to handle this? The plans and instructions don't really tell me much. Any help will be appreciated. [sm=confused.gif]

Thanks,
Robert

RE: 4C engine install on J-3
 

your option. either mount it inverted and have dummy engine showing on both side or mount it sideways with the engine head showing on one side and a dummy engine on the other. I do it the later for better cooling. You can even mount a fuel filler on the top of the fuse just behind the cowl and have it look like the acuale filling location

RE: 4C engine install on J-3
 

Redfox is right, either way is fine. The .72 will be way plenty power, you won't have to work it hard, so don't worry about overheating. The two oval cutouts in the front of the cowl, plus the area around the prop hub, should allow plenty of air in, unless you're going to try hovering:). Just make sure the outlet underneath is larger in area than the inlets. Here are some pics of my Sig 1/5 scale, weighs 10 pounds and flies great with a .65 Saito. I haven't had any overheating problems with mine, nor any of the stuff you hear about inverted engines. I do recommend either an on-board glow or remote glow starter attachment if you invert the engine, as the plug is difficult to get to. Note the scale fuel filler as redfox suggested:

RE: 4C engine install on J-3
 

Thanks for your help guys. I like the idea of having the engine stick out from the side, but the throttle arm looks like its going to sit too high interferring with the cowl. If I can't get that to look right, I am going to have to go with the inverted idea.

Nice cub khodges.

RE: 4C engine install on J-3
 

The side mount is preferable from several standpoints, the main one being you won't flood the engine and bend a crankshaft starting it. Usually, you can bring the throttle pushrod out to one side, run it out a ways and then do a U bend back to the throttle arm. you can make the U bend large enough to fit nearly any installation.

RE: 4C engine install on J-3
 

If your throttle arm is sticking up too high and you want the engine side mounted, try turning the carb around so the linkage is on the other side. Just unbolt the carb from the engine , reverse it, and bolt it back down.

As far as flooding and bending the crank, in a year of flying mine, I've not had a problem with hydraulic lock. The trick is to turn the engine SLOWLY by hand to ensure the cylinder is not full, the exhaust valve will open and drain the excess. If flooding is a problem, use an electric starter. When I start mine, I have to spin it about 3 or 4 seconds, stop, wait a couple of seconds, then spin it again; it always fires immediately on the second spin. Keep the throttle about 1/4-1/3 open while starting. Once I get mine running smoothly, I can shut off the on-board glow, but I generally just leave it on as a backup, since I'm cruising around a lot at 1/4 throttle.

RE: 4C engine install on J-3
 

Khodges your a genius! That worked perfect. This is my first 4 stroke and would of never thought of turning the carb.

Thanks you guys for all the help.

Robert [sm=thumbup.gif]

RE: 4C engine install on J-3
 

Robert, thanks. In 50 years I've been called a lot of things from A to Z, but I don't believe "genius" was any where near the list:). That's one of the things I like about 4-strokes, the reversible carb. I just wish the mfg's would standardize the exhaust thread diameter and pitch so you could mix and match exhausts.