Re: New Piston Rings, Matching, and Cleaning

Kansas John /

You're fine. Put your carb on and run it. The noise, the suction, and the resistance you are feeling are the results of your motor functioning correctly.

When you rotate the flywheel by hand, the piston compresses the air ('cause you've got no carb on it) in the cylinder head. Because you're not running it, you have no spark or explosion to push the piston back down, so there's resistance when you get to Top Dead Center.

When the piston moves upward, it creates (sort of) suction in the cases, which is why your fingers get sucked if you put them over the intake and rotate the flywheel. This is what normally draws fuel/air mixture into your cases which will then be shot through the transfers.

When you rotate the flywheel with no sparkplug in (and no carb on), you're compressing air in the cylinder head quicker than the air can whoosh out of the sparkplug hole, but it IS whooshing out of the sparkplug hole, and that should be what's making that sound.

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