MX | ROADRACE | KARTING | MOPED
Here we explain how to measure the squish size of a cylinder head insert.
You need tin wire and preferably a digital caliper.
You can best measure the squish with tin wire that's close to the expected squish size for an accurate measurement. So if you have an expected squish around of around 0.80, you could best use tin wire of around Ø0.9/1mm. If you have an expected squish of around 0.50, then you could best use tin wire of around Ø0.6-0.7mm.
Note that the squish value in this video (0.38/0.39) is a fictional squish size! It does not mean that you should have a squish size of 0.38mm, the video is made to show you how to measure the squish, not what the squish size should be.
Cut 4 small pieces of tin from a tin wire. Make sure to use 4 and not just only 2 or 1 tin piece to get a correct measurement.
First remove the cylinder head and insert from the cylinder. Then place the 4 pieces of tin on top of the piston, each at 90°. Optionally, you could use a bit of grease to make sure the pieces of tin stay in place.
Click on the picture to enlarge it.
Mount the cylinder head and insert on the cylinder. Make sure to tighten the bolts!
Best to use a torquewrench to tighten the cylinder head (2.2Kgm)! Tighten the bolts crosswise.
Now rotate the crankshaft to make sure the piston moves past it's Top Dead Centre (TDC).
Take the cylinder head and insert off again.
Measure the flat parts of the tin pieces one by one with a digital caliper. The tin pieces should give you all the same (or almost the same) value, they should be equally flat. The value that you measure is the squish size of the insert.