New idea

Maintenance/Repairs
1

i have a new idea for a 2 stroke engine, ok, the gas mix comes in through the reeds like normal lubricating the crank and such, but instead of a tube that lets gas around and on top of the piston, there is a hole all the way through the piston, on top there is a metal spring loaded flap, when the piston goes down, there is a big force that makes it open and lets gas through. when it goes up, the force has changed and the flap closes also because of the spring, it blows like normal, and gas is let out through a side hole like normal, so… what do you think?

2

So, the gas would be fed from under the piston? By filling the crankcase? Or would there be a feed mechanism that could cycle with the piston thousands of times a minute?

No disrespect, but I’m having a hard time envisioning not only the fuel feed but also what the advantage would be over a conventional 2 cycle. Can you elaborate?

3

i doubt this would work, but its fun to think, gas is just fed in through the reeds into the crankcase like a normal 2 stroke, the advantage would be no tubing from the bottom to the top of the piston saving weight

4

I think that 2-strokes are no longer sold in the USA. Where do you live? There is a lot of the world left, but the US is off limits. I doubt that you could even build it here. If you live outside the US, good luck.

5

Here’s a two stroke bike that looks pretty interesting:

http://www.racerxill.com/articles/detail/1022/2007-ktm-two-stroke-intro.aspx

6

all that impressive weight crap was just stupid, the yz 125 im getting weighs like 190 and its a 125 (124) 2 stroke

7

I was just trying to point out that 2 stroke bikes are still available for sale in the U.S. (off-road only).

8

i know, i just wanted to have some input

9

There’s a number of issues. First, any obstructions in the combustion area will affect the burn pattern of the fuel, reducing efficiency. They will also contribute to crevice volume and have a serious impact on emissions (there are low emissions two strokes being sold for outboard applications). Next, you need a flap that will open easily enough to allow the fuel mix to enter the chamber but be robust enough to handle the pressure and heat of combustion. Good luck there. This contraption will also increase the mass of the piston top and that affects the response speed of the engine to changes in throttle. Just a few initial points to ponder…

10

I agree that including a valve in the piston itself would be a design challenge. My guess is that it would not be practical, but it’s an interesting idea.

11

Thanks for the pleasant surprise. I guess that Lawnboy (Toro) doesn’t have the clout that Honda does.

12

Back to the original discussion: You’d have to fill both the crankcase and cylinder rather than just the cylinder. It seems to me that the crankcase would have to be overly full to force enough fuel and air into the cylinder. It also seems like the air/fuel mixture would start to separate in the crankcase since the feed to the crankcase is not fed completely into the cylinder.

13

a 2 stroke already fills the crankcase anyways if im not mistaken, thanks for the input guys, most of you already know this, but this is how a normal 2 stroke works…

14

How about that, the Scott two-stroke engine?! It could be feasible. Let’s see: there’s a valve in the in the top of the piston. It’s placed in the top of the piston furthest from the exhaust port. An arm, connected to the crankshaft throw, would push the valve open at each down stroke. The valve would be easily opened since there is little pressure on the top of the piston near the bottom of the stroke. With the intake through the head of the piston, the exhaust port could be made longer, perhaps to the edge of the piston at bdc (bottom dead center). This could result in increased efficiency. I think that a hole for the valve in the head of the piston isn’t an insurmountable design obstacle.

15

Intake valves in the piston crown were used in Gnome rotary radial aircraft engines during WW1. This was a four stroke engine however. The crankcase served as the intake manifold. The head had a single exhaust valve in it opened by a camshaft, the intake valve in the piston crown was opened by the suction of the intake stroke. The valve had a counterbalance weight to compensate for the piston acceleration. It was a big maintainance item and one of the primary reasons that these engines only averaged about 18 hours between overhauls.

16

It works great until the explosion. The little valve gets too hot.