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i have a thumpster 107 and i want to put a big bore kit on it. what have you guys used and were is a good site to find them at
 

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upping the compression will wake it up...most those stocker China motors are mediocre...the Firepower can get ya a big lump for any slug you want in that 107...you should see the slug he got for my 138 from Akunar



Sir Edmund Hillary (guy who climbed Mt Everest) would not even tackle that hump...lol
 

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jerryrice#3 said:
how much difference in performace does the 114 big bore kit make in a 107.


The added cc's help, but the squeeze really wakes them up. Even a stock-bore hi-comp adds noticeable torque through the range. The alloy 114 jug is a nice feature, though, and "Cubes is King":)
 

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The compression ratio of an internal-combustion engine or external combustion engine is a value that represents the ratio of the volume of its combustion chamber; from its largest capacity to its smallest capacity. It is a fundamental specification for many common combustion engines.

In a piston engine it is the ratio between the volume of the cylinder and combustion chamber when the piston is at the bottom of its stroke, and the volume of the combustion chamber when the piston is at the top of its stroke.[1]

Picture a cylinder and its combustion chamber with the piston at the bottom of its stroke containing 1000 cc of air (900 cc in the cylinder plus 100 cc in the combustion chamber). When the piston has moved up to the top of its stroke inside the cylinder, and the remaining volume inside the head or combustion chamber has been reduced to 100 cc, then the compression ratio would be proportionally described as 1000:100, or with fractional reduction, a 10:1 compression ratio.

A high compression ratio is desirable because it allows an engine to extract more mechanical energy from a given mass of air-fuel mixture due to its higher thermal efficiency. High ratios place the available oxygen and fuel molecules into a reduced space along with the adiabatic heat of compression - causing better mixing and evaporation of the fuel droplets. Thus they allow increased power at the moment of ignition and the extraction of more useful work from that power by expanding the hot gas to a greater degree.
 
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