I'll report back on how it runs. Easy conversion though, as suggested by another on the board.

Looking good so far! Keep us posted.

J

How is the lubrication facilitated with these engines?

Lube? They use some 30 wt in the crankcase.

I ran it yesterday, it kept going lean....got POed. It only ran with the choke on.

Did some research. Bent up the pop off lever about 0.01". Opened up the main jet a little using a half reamer made out of a sewing needle. I can't say exactly how much though, perhaps a few thousands. I suspect the pop off lever did most of the good. It now runs properly without an air cleaner! It still rubs me the wrong way not not have ajustment screws. Anyway with a Bambula 22 x 8 it idles reliably and crazy slow. Below 1200 something starts to click in the engine. It spins up to 5500 with no hesitation. It seems to run in the mid 5K range with most every reasonable prop. A Mens 24x10 does bring it down to 4900. A 20x8 only spins up a little faster than the 22x8. For yucks I tried a 16x8, only 7500. Removing the muffler gained about 500 RPM. I opened up the exit holes and tossed the screen and got back 300. It is not loud without the muffler. If I actually fly it I will probably make a header.

What about the long intake manifold? I'd like to make a short one. This engine gets the pulse for the carb from the intake manifold. Do I need the long intake plenum to make the pulse work? Or, is it simply the engine sucking in the charge that makes the pulse? I guess I could make a long plenum by installing the carb on the firewall, or behind it, and use a bit of rubber hose to connect it to an intake manfild stub tha bolts to the engine.

I cut down the stock manifold. Someone else made one out of plywood(!). Another gent used a Ryobi manifold. Many ways to skin the proverbial cat.
If you haven't done so yet, you should do a search under "Briggs" and also "B&S" as there is lots of info to be gleaned.

J

Thanks I'll machine one out of 1/2" plastic stock. That will give an oppertunity to rotate the carb so that I get a striaght shot to the servo.

So, the location of the port that connects pulse hole of the carb does not matter? Would it work out to make a notch or furrow that connects the carb port to the intake plenum?

I just thought of this. Plastic cutting boards might make good intake manifold stock. I tend to use my bandsaw, drill press and dremil for these things. A forsner bit cuts plastic real clean.

Nylon chopping boards ... kitchen variety ... are a very cheap and useful source of material.

I made a little intake plate out of 1/4" phenolytic. Runs great! Now to thin it further I will need to switch over to an ignition module. I will also make a different exhaust setup to eliminate the big bulky box muffler.

I ran it next to my other choice for my BUSA Fokker D-7, an EFCO 39cc chainsaw conversion. That one fits with nothing protruding. It runs 800 RPM faster with the same prop. It shakes more though. The 4-stroke is really smooth and idles down really good. Very quiet too, it sounds neat. The thrust on the 4-stroke will be about 80% of the weight of the airplane, that should be pleanty. It will mess up the looks of the dummy engine though. There are certainly trade offs but, I am warming up to the Briggs.

The clicking sound is most likely the compression release.

Where is the compression release? I don't see a button on the head like on a big chainsaw.

The compression release is usually a centrifugal lever that acts on the exhaust valve. Works different from a 2-stroke.

Most FOUR STROKE industrial engines have an automatic release built in to VALVE TRAIN THE TITLE SAYS "Briggs 40 4-stroke "

THE TITLE SAYS "Briggs 40 4-stroke" DUR