Main ingrediant: The 300 cylinder comes with all the hardware.
Numbers game: MXA’s KTM 300SX engine kit gained 5. 5 horsepower at 7000 rpm over the stock 2014 KTM 250SX.
measuring with a micrometer from the top edge
of the cylinder to the bottom of the flapper. The
measurement must be 48.5mm. We got it right with
only one adjustment.
Q: WHAT IS THE SECOND-MOST CRITICAL
A: To get the piston located properly in the
cylinder, you have to measure the deck height.
Luckily for the home mechanic, KTM has a very simple
method of setting the proper deck height. It requires
no milling or mechanical work. The KTM 300cc
PowerParts kit comes with five different thicknesses of
base gaskets. These base gaskets can be used
individually or stacked together to create a panoply of
different deck heights.
To check the deck height, install a base gasket
under the cylinder and then tighten it down without
the cylinder head in place. Then, place a straightedge
across the top of the cylinder and bring the piston
up to top dead center. If the deck height is perfect,
the top of the piston will barely kiss the bottom of
the straightedge. If it comes up too high, remove the
cylinder and install the next thickest base gasket. If it
doesn’t come up high enough, install the next thinnest
base gasket. In our case, we started with the stock
0.6mm base gasket and the deck height was perfect.
Just to double-check, we borrowed a special deck-height dial gauge from KTM and used its dial to check
the accuracy of our work. It confirmed that we were
spot on. KTM sells this deck-height dial gauge from