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What Is Displacement? Big Bore Kits & Stroker Cranks
[28,465 views - 11 comments - Rating 5/5 ***** ]

If you're here for the GY6 displacement calculator, click here to jump directly to it.

What is displacement?
The size of a piston-driven gasoline engine (like the GY6 in our buggies) is measured by displacment of it's internal combustion chamber. The term displacement literally refers to the volume of space the combustion chamber "displaces", and is usually measured in cubic centimeters (cc's).

Displacement, there's no replacement!
The reason displacement is so important in engine design is that in general there is a direct relation between the amount of displacement, and the amount of power ultimately produced by the engine. There are a lot of other factors, but as the old saying goes: "there's no replacement for displacement!"

Just like when measuring the internal volume of any cylinder (like a can of Cola, which is 355cc by the way), displacement of an engine is determined by the bore size (diameter) and stroke length (depth). Bore size is simply a measure of the piston diameter. The stroke length is how far the piston itself travels inside of the cylinder. For example, the standard bore of a 150cc GY6 piston is 57.4 millimeters, and the piston travels 58 millimeters within the cylinder every cycle.

Bore x Stroke = Power!
The more displacement an engine has, the more air and fuel mixture it can suck in from the carburetor. The more gas and air you can confine into a space and ignite, the bigger the boom! This translates to more power at the wheels of your buggy. The internal volume of the engine can be upped by either increasing the bore or the stroke sizes. While these both do the same thing, they are not created equal. This leads us to the next point...

Why strokers are important.
Stroked engines not only have a larger displacement than a stock engine, but there is also a greater amount of torque produced per additional CC when compared to only a bigger bore. This is because a stroker crank produces more leaverage than a stock crank. Think of it like this, it is much easier to remove a stubborn rusty bolt with big wrench than with a small wrench, right? A bigger wrench will take that bolt off easier because your hand travels in a larger diameter circle, resulting in more torque being applied directly to that stubborn bolt. It's all about leaverage and the same principle applies to the crank shaft of your buggy. A longer stroke means that the piston (your hand) has an easier time turning the crankshaft (the wrench) and ultimately the rear tires (the bolt). Got it? Cool, we're ready to start playing with numbers...

Calculating displacement.
So you've read everything above (or maybe not...) and you want to see what the actual displacement of your GY6 engine is. That's good, because we happen to have written this nifty little displacement calculator to hook you up with exactly the info you're after. Here you will find all of the bore and stroke options currently available in the GY6 market, so that you can see all possible displacements with a few clicks of the mouse.

GY6 Displacement Calculator

Choose an available GY6 bore diameter:

Choose an available GY6 stroke length:

The Result:
The displacement of your GY6 is: 150.09cc!

By the way... we offer 57.4mm and 62mm cylinder kits in the Online Store, as well as the 60mm stroker gy6 crankshaft.

Also, 58.8mm is the largest size bore that can be installed on the GY6 engine without machine work to the crankcase halves.

If you don't know what bore diameter or stroke length are, read above!

This article has been downloaded 28,465 times
11 comments about this article:
Poster #1 [11/19/10]
yes! i like the displacement calculator.
Poster #2 [11/27/10]
I'm a old master certified and award winning diesel and gas mechanic (big rigs mostly). If I can learn (or at least be reminded) from your page I just read, and I did, then it should be a help to anyone. Well done!
Poster #3 [02/09/11] Rating 5/5 *****
good article, very well explained in the most basic of terms. Thank you!
Poster #4 [09/29/11]
Could you add the larger stroker lengths to the gy6 displacement calculator... Up to the 8mm stroker...
Poster #5 [02/10/12] Rating 5/5 *****
well written, well exsplained.
Poster #6 [07/26/12]
Poster #7 [01/12/13]
Great article, really enjoyed it.
Poster #8 [03/31/13]
idk much but mine is stroker 300... how do i calculate the stroke length?
Poster #9 [04/30/13]
It's funny because I've installed NCY's 61mm kit in a gy6 before, no machining required.
Poster #10 [06/30/13]
where can I find the formula you used.
Poster #11 [06/30/13]
Some 61mm kits makers like NCY machine the cylinder sleeve to be more narrow and fit without machining, but it costs reliability and they don't hold up in the long run. If you expect to be able to run the engine to it's full potential, you'll find out real quick that the weak thin area on those "no machining needed" 61mm cylinders will snap and wreck the engine if your jetting goes too lean for even a minute under WOT and high RPM. The piston sideloads that weak area on every stroke, so it's especially bad if adding a longer stroke crank as even more force will be transferred to the thin area.
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