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So I was playing around with this engine I got it started and it runs great but just a little curious what the port on the bottom of the crankcase is for. I had it running for about 20 minutes it had good transition off idle but never sounded like it was reaching high rpm's , and acts like its backfiring at full throttle. I ordered a tach and I'm gonna pull the carb off and give it a good cleaning and try to tune it again.

The pressure tap on the bottom of the crankcase present with many four stroke (not all) is a a crank case breather/vent. Keep open, yes you can run short lines out of the cowling but keep short. These breathers will drip some oil/gunk.

John

Definitely put a tube on it and run it out of the engine compartment.
If you don't you will saturate the engine compartment with oil.
If it is not meticulously sealed you eventually saturate the wood.

An ounce of prevention is worth a pound of K2R.

Good Luck,
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