Cylinder squish clearance

[Tonkaman]

Can someone help me understand how to measure the clearance between the piston and valves? I know some people use solder wire and some use clay but I don't totally understand the process.

My new piston sticks up past the cylinder in the middle but has valve reliefs so maybe it's not an issue.

Any insight is helpful

 

[anderson750]

I don't know how to measure it on a 4t, but when I do it on my boys 65 I put a piece of .050 solder through the spark plug hole and point it to the left side of the piston. I then repeat it for the right side to make sure they are within .002 of each other.

 

[Tonkaman]

I've done it that way on a a 2 stroke but it was a basic dome piston going into a dome head. My head has 4 valves coming out at an angle and the piston is flat with angled valve reliefs. I'm going to put clay on the piston and rotate the engine over to check clearance.

 

[Tonkaman]

Well since my main concern was to be sure there was adequate clearance I went ahead and used putty. I rolled 3 strips and laid them across the piston, one over each valve relief and one across the center. Its pretty hard to get an accurate reading from putty but Im pretty confident that I have atleast .090" clearance from my intake valves to the piston and that is the closest point. If I were really trying to squeeze the power out of this bike I might mill the head down to close that to about .040" but Ill play it safe.

 

[jeeper]

I can't wait for this to be done!

 

[gijohn40]

just remember when things heat up they expand... so that .090 will shrink some when its hot..