So I am going through the carb on the 78 dt400 and it ran perty rough. I was able to spray carb cleaner through most of the ports that I saw. However, in the carb inlet there are 3 air ports together at the bottom of the bell housing, one plugged at the factory with a brass plug on the left, and two not plugged. I have a question about the one on the right. I can't seem to get the spray carb cleaner to come out on the other end (wareever that may be). I was wondering if it is a through port or blocked at the other end. And if it's blocked will it effect carburetion.

I'm trying to recall my 78 DT400 but that hole may go to the bottom of the choke hole. Spray it again and see if you get anything into the bottom of the choke hole. May be wrong on that but check it out...

Thank you brother. Yah, no joy I tried the middle hole and that went to the needle jet. The upper hole that sits by itself went there to choke.

Normally only the hole on the side of the air screw is open. The other is blanked.

If air screw was on left, hole on right would be blank.

In the later years, probably for emissions, they vented the air screw passages differently which is why there is a brass ball in the left passage. If you removed that ball, passage goes to the idle air screw.