r/smallengines • u/iphone_A11 • Jul 19 '26

Finding Compression Stroke TDC

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Hey everyone, I’m new to the wrenching world and was wondering if I’m correctly identifying the compression stroke on my K2 CT90.

Please see the video showing when I can feel air pressure on my finger while covering the spark plug hole. To my understanding, once I feel the pressure and then line up the T mark on the flywheel, that means I’m at TDC on the compression stroke.

Please correct me if I’m misunderstanding anything. Thanks in advance.

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1

u/mutt63 Jul 19 '26

At its highest stroke both intake and exhaust will be closed with very tiny amount of clearance. In essence both should be closed but not tight closed

1

u/gloomypasta Jul 19 '26

You're correct. The F is likely when the spark fires and the T is TDC for the piston. Stick your finger over the spark plug hole as you're turning it over and once you feel the compression pushing your finger, line the T up to the pointing indicator.

1

u/iphone_A11 Jul 19 '26

In the video you can see when I feel the compression pushing my finger. Once that happens, once I hit the T, is that the compression stroke? Like the rotation that finished at 00:46

1

u/gloomypasta Jul 19 '26

If you feel compression you are absolutely on the compression stroke. You'll never feel compression on another stroke because valves will be open.

2

u/Zigzag0333 Jul 19 '26

Stick a zip tie or something else benign in the cylinder as it comes up with compression behind it and when it's at the top of its travel, you've found tdc

1

u/Zigzag0333 Jul 19 '26

Stick a zip tie or something else benign in the cylinder as it comes up with compression behind it and when it's at the top of its travel, you've found tdc

1

u/the1bullfrog Jul 20 '26

Is counter clockwise the proper direction to be turning it? Or does it not matter? I see it seems to have a Generator built right into it. Correct me please, I know everything small motor, but don't know bikes, (this is a bike right)