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Carb port plugged up?

29 Sep 2020 16:52
FrankC
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Carb port plugged up? #1
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.

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29 Sep 2020 18:43 29 Sep 2020 18:45 by Pedalcrazy.
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Carb port plugged up? #2
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...

1978 DT400E
1976 DT400C
1973 RT3
1971 RT1B
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29 Sep 2020 19:17
FrankC
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Carb port plugged up? #3
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.
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29 Sep 2020 19:56
MarkT
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Carb port plugged up? #4
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.

1963 YG1-T, 1965 MG1-T, Allstate 250, 1970 CT1b, 1971 R5, 1973 AT3MX, 1974 TS400L, 1975 RD350, 1976 DT175C, 1976 Husqvarna 250CR, 1981 DT175G, 1988 DT50, 1990 "Super" DT50, 1991 RT180, 2017 XT250
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