Monosoupape type engine running -Briggs & stratton

Here is the Monosoupape type 4 stroke engine that I put back together. This engine operating cycle was developed during WW1 for use in Rotary type engines (the whole engine block rotated along with the propellor, so the engine itself acted as a flywheel. The crankshaft was bolted to the airplane, and didn't rotate, the crankshaft was hollow, and the gas-air mixture was feed to the engine thru the hollow crankshaft.)
My adaptation of this engine concept uses both existing valves as exhaust, with inlet ports in the cylinder that are uncovered by the piston close to the bottom of the stroke.
I also changed it so that the intake ports connect to the original intake manifold, which is blocked off near where it bolts to the block. It is ground out to allow the intake valve to exhaust outwards, while the remaining part of the manifold mount holds the intake manifold in place, to allow the carb and gastank to remain in their original location.
The modified operating cycle of this engine is described in my other vid about the monosoupape.
My engine has oil in the crankcase, and has run about 10 minutes straight, and cut grass. It smokes badly due to a scratched cylinder, and the inlet ports could be a contributing factor. It can be throttled to a certain extent, but always needs at least 1/2 choke to run rich enough.

I Always use Briggs and Stratton engines, as I don't need any unexpected holes in the block due to a broken connecting rod, as might happen when using other un-named engines!!! :)

Category:

Education

Tags:

• monosoupape
• engine
• Briggs
• and
• Stratton

[shinyfuzzy]

i saw a 2hp briggs and stratton verticle shaft engine in the junk yard the other day... is it rare? ive never seen one b4. in was on one of those lawnboy type mowers with the wierdd deck design but i think it was a knock off

[ChargerMiles007]

@shinyfuzzy

I would say it is fairly rare, since it is probably from the early 1960s.

I personally have no idea if any of this stuff is collectable, or worth anything other than to us Briggs Guys :)

[shinyfuzzy]

@ChargerMiles007 u would love this junkyard btw, tons of briggs 3-5hp engines and lawnmowers just stacked

[ChargerMiles007]

@shinyfuzzy

Really, it sounds like a real Briggs Haven!!!! <3

Unfortunately, the garage I had my stash stored in is being sold, so I have a ton of them all sitting on my lawn!!!

I always look for the long crankshafts on the 3.5hp mowers, since I need them to mount the chain speockets onto to make my FrankenBriggs engines :)

[ChargerMiles007]

@tpvalley

Glad I explained that OK, I never know how well I explain things sometimes, and the 500 character limit doesn't help matters any!

[tpvalley]

@ChargerMiles007

ah, I see.

[ChargerMiles007]

@ChargerMiles007

...mixing a very rich mixture from the carb, with the air already in the cylinder that came in thru the exhaust valves. Then the piston goes up on compression, then power like a normal engine.

Somebody sure had their thinking cap on to figure all that out!

It was a bit hard on exhaust valves due to the fact that they were subjected to hot exhaust, then fresh cool air.

[ChargerMiles007]

@tpvalley

It is a 4 stroke engine, but uses a modified cycle.

On power stroke, both valves open very early for exhaust, this bleeds the pressure down, so that when the piston uncovers the small inlet ports, no exhaust goes into them. The piston goes up on exhaust, then the valves stay open past TDC, about 1/3 of the way down in the inlet stroke, pulling fresh air in thru the ex. valves. A high vaccum developes when the valves close, around BDC, inlet ports are uncovered, mixing rich mixture..

[tpvalley]

@ChargerMiles007

what draws the fuel air mixture through inlet ports if its not blown or using the crank case like a 2 stroke?

[ChargerMiles007]

@tpvalley

Actually, this one just uses oil in the crankcase, it is only the "Piston Valve" engine that has gasoline/oil mix in the sump.

This engine uses ports in the cylinder wall for inlet ports, and both poppet valves are for exhaust.

I actally re-used this block for the inlet block on my Jumo 205 engine, I also use it for the supercharged 2 stroke Briggs. I have a new block with larger inlet port holes, for use on the Jumo 2o5, but the manifolding takes some time to do, I got lazy! :)