Baby Hog,
I've included a little info on 2 stroke vs. 4 stroke. I appologize if you already understand the difference. I think what Earlytimes was getting at is that modifying a 4 stokes breathing ability can have noticible gains while a 2 stroke not so much. So when Bill mentioned the 2 stroke motor ......... a 2 cycle fires every stroke, a 4 cylinder every other stroke. Sooo a 2 cycle fires more per RPM than a 4 cycle engine.

How They Work
There is a marked difference in how a 2-cycle and 4-cycle motor operates. A 4-cycle engine works, as you might expect, in four stages. There is the power (down) stroke, the exhaust (up) stroke, the intake (down again) stroke, and the compression (up again) stroke. It takes two full revolutions of the crankshaft to deliver these four strokes. It's the power stroke which sends the piston through each of the three remaining stages.

A 2-cycle engine literally has just two cycles that combine the above duties. The first stroke is the combination power and exhaust stroke and the second combines the compression and intake stroke. Both power and combustion happen as the piston reaches to top of its stroke. At the bottom, the exhaust and intake occur. It takes just a single revolution to generate two strokes and propel the piston through its full cycle.

More Parts = More to Break
Four-cycle engines have a lot more moving parts. They have a crankshaft, camshaft, connecting rod, valves, lifters and of course the piston. A two-cycle engine really has only three major moving parts. This includes the crankshaft, connecting rod and the piston. In small size two cycle engines there are no cams, lifters or valves. As a general rule, less parts equals less potential for failure and easier maintenance. Overall, the 2-cycle engine is typically smaller in displacement and size as compared a 4-cycle which, many times, is almost double the displacement and overall size to achieve the same power. The reason for this is because since the 2-cycle combines two functions in one rotation, it makes the power  twice as quickly as a 4-stroke.




The fact is, 4-cycle only has a few advantages: greater potential torque, higher fuel economy, and better emissions.


Greater Potential Torque = The reason we are playing with it

Burn,Gort is right

bill67 wrote on 06/09/10 at 11:14:18:


about?

BurnPgh wrote on 06/09/10 at 11:30:30:

You called me Gort

Thats OK he's a good guy.

Bill, I was only highlighting the potential. I would never get into that arguement.
Either motor could come out on top for power, there are so many mods for either one.
Just saying the porting the exhaust on a two stroke is harder to get precise, you would also have to increase the intake pressure due to the short time that the valve are open. Many use blowers to increase how much fuel gets in. With a 4 stroke you have a lot more leeway for error.
I do understand your point about the needle jet increase, either way more out will need more in. Thank you for that.

"Two-strokes produce far more power than four-strokes, but in motocross, peak horsepower is a secondary consideration – it’s not so much about how much power gets to the ground, but in the way in which it gets there. A two-stroke’s power explodes over a short period, whereas the four’s is more linear and results in a far wider power-band. Torque is everything, and four-strokes have it in abundance.

The benefits of having usable power across a wider spectrum are many. For starters, on a four-stroke you don’t have to spend as much time changing gears, and therefore you spend less time with the throttle partially disengaged. The linear power also encourages the rear tyre to grip instead of spin, and its predictability makes it an ideal choice for the lesser-skilled rider."

So,.. it's more about the width of the powerband...
2 strokes make what they make in a narrow rpm band... That's why 4 strokes are considered torqueir...  (torqueir?)... ...

I'm not talking about moto cross or race bikes,I'm talking about street bikes.I had a suzuki 550 and 750 2 cycles,They don't have the narrow powerband of a race bike.At 50 mph a Suzuki 750 2 cycle would stay even with a 750 Honda by 60mph it was running away from the Honda,And the Honda was turning more rpm.I would have to say the Suzuki had more torque this was all in high gear roll ons.