Can some one explain "squish"

[dicedealer702]

Can some explain to me what " squish" means... ???????

[dirtydownunder]

these are squish bands..

 

the squish band helps push the air / fuel mix into the center of the combustion chamber for a better burn when it ignites, it also helps disperse the power around the piston.

 

when measuring squish on an engine, you are measuring the clearance from the edge around the top of the piston, to the squish band around the dome (combustion chamber)

 

you need the proper amount of squish when building an engine ( not all engines have squish bands, mostly 2 strokes have them) too much and your engine wont run to its optimum, not enough and it will detonate and run poor, or no clearance and your piston will make love to your dome.

[sprinklerman]

Excellent post , Dirty. Just to add to it a bit, to check your squish clearance, a common method is to use some hollow solder down through the spark plug hole. As you turn the engine over by hand,,SLOWLY,,the piston compresses the solder piece and that end of the solder is measured to get your squish clearance.

Make sure the solder piece goes all the way to the edge of the cylinder.

Also make sure the solder is running the same way as the pistons wrist pin so that the piston wont rock and give a false reading. I prefer to use 2 pieces of solder at the same time, facing away from each other so that the piston doesn't rock.

[crustydemon]

It should measure right around .045.

[BigRed350x]

It should measure right around .045.

 

Squish will vary from bike to bike, dome to dome. You will get different opinions from different people on what is optimum. Anywhere from .035" to .055" is pretty normal. I know K&T likes a pretty tight squish.