Simple CT90 Valve Seat Check/Inspection

One of the best things you can do to your CT90 is to make sure your valves are seating and sealing to ensure that you have adequate compression. If you have your head pulled off the engine an easy way to check how well your valves are seating is with a small LED light.

In the picture below I am holding the light I use and it was a cheap LED light that has a flexible gooseneck that makes it easy to stick into tight places and is a pretty common light you can find usually on the counter at your local auto parts store.

What I'll do is turn on the light and then insert it in through the intake or exhaust port until it is up near the backside of the valve I am interested in.

At that point I turn off the lights in the room and carefully look around the edge of the valve and see if there is any light coming through.

If there is light coming through like in the picture above then I pull the valve and either lap the valve & seat or cut/grind the seat and then lap the valve and seat.  When I follow this approach and get the valves to where there is no light visible, then I always have good compression (assuming the piston and rings are good).


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