Check Deck

Setting the deck height or X Dimension is critical to perfformance. Most manufacturers have an optimum spec for this setting.

Generally this setting is 0.00". Some tuning tricks will vary this setting +/- .010" . Most models can use the method above to check the Deck / X Dim. Shown is a KTM 125/200, This model uses a design that has the  cylinder surface recessed slightly. Other models are flush anf have a flat cylinder mating surface.

To check the clearance I use a Zero Block, that foems a straight edge accross the mating surface. Any straight edge trimmed to the proper width for a recessed cylinder will work. This works for a flat top piston and up to a Zero Deck spec.

For domed Pistons you can measure at the very edge. When setting piston above the deck, feeler guages can be stacked to help get the height required.

There are other tools out there, try the simple version first and see if it helps.