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Hi All... just thinking with a spark at every stroke has anyone ever built a 2 stroke airhead?
Just wondering.
Uncle Mark

Hate to burst your bubble, but there is far more to a 2 cycle than when spark arrives. I'm pretty sure the BMW engine would not last too long using its crankcase as the pressure element for 2-cycle operation. Fuel-air mixture with a "dab" of oil is unlikely to provide many minutes of enjoyment before the bottom end is entirely melted from inadequate lubrication...

But I'm just guessing here - stranger things have happened...

There are lots of 2 stroke motors that don't use the crankcase for primary induction. You would use the existing pressure lube system, lose the cam and valve stuff. I think the piston ported design could be handled I just don't know what to do with extra heat short of water cooling the heads and Barrels. I see some water cooled heads on high output kitted scooters and some are fairy simple.
Just thinking about a lot of extra HP.

uncle mark wrote:There are lots of 2 stroke motors that don't use the crankcase for primary induction.

Huh?????

I do not know of a gasoline two stroke that does not push the charge into the cylinder from the crankcase. I don't know how 2-stroke diesels work.

What are these other designs?

Major Softie wrote:

uncle mark wrote:There are lots of 2 stroke motors that don't use the crankcase for primary induction.

Huh?????

I do not know of a gasoline two stroke that does not push the charge into the cylinder from the crankcase. I don't know how 2-stroke diesels work.

What are these other designs?

GMC 2 stroke diesels have 4 exhaust valves in the head and intake ports in the cylinder sleeves fed by a roots type positive displacement compressor. Injection is by an injector operated by a rocker arm similar to the valve rockers. The lower end is much like a 4 stroke engine. They are big, ugly,dirty and noisy.

robert wrote:

Major Softie wrote:

uncle mark wrote:There are lots of 2 stroke motors that don't use the crankcase for primary induction.

Huh?????

I do not know of a gasoline two stroke that does not push the charge into the cylinder from the crankcase. I don't know how 2-stroke diesels work.

What are these other designs?

GMC 2 stroke diesels have 4 exhaust valves in the head and intake ports in the cylinder sleeves fed by a roots type positive displacement compressor. Injection is by an injector operated by a rocker arm similar to the valve rockers. The lower end is much like a 4 stroke engine. They are big, ugly,dirty and noisy.

That sounds like fun!

........That sounds like fun!.........

Until you have to rebuild one.

I considered getting into the alternatives like forced induction, but that is not in the spirit of the OP's post. Also, because 2-cycles are mostly RPM (and not a whole lot else) when you put one on a dyno, you'd likely see they are not highly suitable for something as big as our street bikes; their torque curve, power band and HP is not at all what would please most and you'd need at least a five or six speed tranny to make you and or it happy.

You also would likely never make it across the CA boarder with it either... CA's could confirm, but I thought the no more 2-cycle emission laws are already in place out there and have been for a while...

Alas, nothing is impossible, we could perhaps figure a way to put a tinder box under a BMW and run a sterling on Helium or something, but would likely then lose a race with one of those "Hover-Round" carts disabled people use to stay mobile...

uncle mark wrote:There are lots of 2 stroke motors that don't use the crankcase for primary induction. You would use the existing pressure lube system, lose the cam and valve stuff. I think the piston ported design could be handled I just don't know what to do with extra heat short of water cooling the heads and Barrels. I see some water cooled heads on high output kitted scooters and some are fairy simple.
Just thinking about a lot of extra HP.

You have me interested. Yes I have seen forced induction 2-cycles - a handful of them, OK maybe a palm full. You use the word "lots" where are all of these? I don't mean on wikipedia - like we were going to put a sterling in our bike - sure it's an engine but not going to make our BMW's go. Drawings, animations and the like are one thing, actually operating equipment another. I mean no disrespect, but I handled 2-cycles daily for many years of my youth and not one of THOSE production 2-cycles were forced induction engines - reed or rotary and the down-stroke was where the charge was created to allow the fuel-air mixture to be shot into the cylinder and carry out its two duties. Not a single weed-eater, lawn mower, winning dirt bike, nothing that was actually a production unit have I ever seen made differently. All the forced induction stuff I've seen were novelties. I think above someone mentions a production GM product; that may be a 2-cycle(s) literally, but what was depicted sounds a lot more like some of the oddball diesel types that have come and gone.

EDIT: --> They indicate the GM product is/was in fact is a diesel as I suspected; sorry about that...

dwire wrote:I think above someone mentions a production GM product; that may be a 2-cycle(s) literally, but what was depicted sounds a lot more like some of the oddball diesel types that have come and gone.

EDIT: --> They indicate the GM product is/was in fact is a diesel as I suspected; sorry about that...

Yeah, it's the "Detroit Diesel" that is a 2-stroke. I'm very familiar with their existence, and even their sound, but I never knew exactly how they worked. Looking it up, I find that the 2-stroke diesels were what revolutionized the railroads and moved them all to diesels.