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Old 08-03-2011, 08:44 PM
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Default 2 stroke poppet valve briggs

Here is a rough sketch of what I want to make. The exhaust valve will never open. I will Grind the lobes the the exhaust so it dosent open. The Exhaust port will be ground out and I might haft to Make some pins so the piston rings dont spin and catch in the port. What do you guys think?
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Old 08-03-2011, 09:42 PM
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How are you planning on modifying the cam so that it opens every other stroke?
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Old 08-03-2011, 09:43 PM
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How are you planning on modifying the cam so that it opens every other stroke?
Weld the cam so it looks like a football then fine tune it with a dremel till I get it right.
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Old 08-03-2011, 09:44 PM
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How is the exhaust going to be evacuated from the combustion chamber? 2 strokes circulate fuel/air mixture through the crankcase so that the downward action of the piston forces the mixture into the combustion chamber.
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Old 08-03-2011, 09:50 PM
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How is the exhaust going to be evacuated from the combustion chamber?
The sketch is kinda rough but the port is higher up and the intake valve opens alittle later so when gases start coming out of the port the intake valve will open.
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Old 08-03-2011, 09:54 PM
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The sketch is kinda rough but the port is higher up and the intake valve opens alittle later so when gases start coming out of the port the intake valve will open.
But theres no mechanism to clear the chamber. With your design, the engine will fire once, then quit running.
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Old 08-03-2011, 09:59 PM
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But theres no mechanism to clear the chamber. With your design, the engine will fire once, then quit running.
When It fires there is pressure and once the port is uncovered it blows out the gasses and when it starts releasing the pressure it pulls a vacume at the top of the cylinder and pulls in fuel + air. But you may be right
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Old 08-03-2011, 10:01 PM
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When It fires there is pressure and once the port is uncovered it blows out the gasses and when it starts releasing the pressure it pulls a vacume at the top of the cylinder and pulls in fuel + air. But you may be right
The problem is, this would rely entirely on the air being siphoned out of the chamber, which wouldnt clear the chamber nearly quick enough.
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Old 08-03-2011, 10:23 PM
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he would have to off set the cam or something idk, its to late at night to think about this real hard haha
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Old 08-03-2011, 10:23 PM
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Quote:
The problem is, this would rely entirely on the air being siphoned out of the chamber, which wouldnt clear the chamber nearly quick enough.
What if I used the Intake and exhaust valves for intake?

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he would have to off set the cam or something idk, its to late at night to think about this real hard haha
I already said I would haft to weld and grind 2 lobes on the cam.
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Old 08-08-2011, 03:05 PM
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Quote:
Originally Posted by devino246 View Post
2 strokes circulate fuel/air mixture through the crankcase so that the downward action of the piston forces the mixture into the combustion chamber.
dont have to work like that.


possible solution would be to use an external device such as a supercharger/turbo charger/charging piston to compress the charge. Cut/drill an intake port into side of barrel and use one or both of the original poppet valves for exhaust. Incoming compressed charge would be used to scavange the exhaust.


altho i think you would have to be a mega scientist to make that work(if it is even possible) and would require complete re-engineering of the engine lol

silly idea probably, im no scientist.

go buy a twostroke
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Old 08-08-2011, 06:49 PM
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or just go for it and see what happens. sometimes stuff just works.
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Old 08-08-2011, 09:25 PM
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or just go for it and see what happens. sometimes stuff just works.
If by some miracle it works, it will be completely useless.
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Old 08-09-2011, 12:44 AM
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^well i have to agree accept over the last week i have witnessed the most absurd engine concept ever, be built and then run.

two ironhorse towstroke engines with the heads bansaw'd off, joined together with a spacer in between, both engines sharing a common combustion chamber lol. I was like "**** that wont work". But then it did
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Old 08-09-2011, 03:58 AM
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The $50 question is- Why?
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Old 08-09-2011, 08:49 AM
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Quote:
The $50 question is- Why?
If it works on a small briggs and sratton it will work on a big briggs and stratton. 2 strokes produce more power. Do this to a 400 some CC 10hp briggs and how many horsepower would you get?
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Old 08-09-2011, 11:53 AM
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Quote:
The $50 question is- Why?
Yes, why?
One of the main reasons for the development of 2 cycle power plants was to eliminate the entire valve train and use what is already there. As a result they weigh about half that of a 4 cycle.
Even if it worked, it would not be practical.
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Old 08-09-2011, 01:23 PM
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Four strokes are not designed to be run like 2 strokes!
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Old 08-10-2011, 05:04 PM
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Quote:
Originally Posted by karl View Post
If it works on a small briggs and sratton it will work on a big briggs and stratton.
With that argument, I could go out and 2-stroke the 318 in my truck!
Anyways, not without a ridiculous amount of re-engineering.

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2 strokes produce more power.
Due to the elimination of many power-robbing moving parts, like the valvetrain.

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Do this to a 400 some CC 10hp briggs and how many horsepower would you get?
Unless you have one he// of a machine shop and a ton of time and material on your hands, less than 10!

Hey- take a whack at it, go ahead. Just don't bet the farm on it.
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