I was having a similar issue with the old carb on my 73 courier. I could never figure out how vacuum was used to open the second barrel since vacuum is higher the less load you have on the engine (full throttle should have minimal vacuum if not 0) I gave up and replace the Hitachi unit with a Weber and it runs better, has more power, and gets better fuel economy.
Wish I could have afforded a Weber, would have made things a LOT easier!! I had a heck of a time finding any good information on how to properly "tune" these smaller carbs. Most instruction sets are for LARGE V-8 carbs. All I could find for a small carb was that you have to "fiddle with the set screws until you got good results." Well, I wasn't getting any results one would call good. Oddly enough, I stumbled upon a video from the Philippines (in Tagalog) that showed exactly how to do it. Copied the video step-by-step and it tuned up perfectly!!
I was having a similar issue with the old carb on my 73 courier. I could never figure out how vacuum was used to open the second barrel since vacuum is higher the less load you have on the engine (full throttle should have minimal vacuum if not 0)
I gave up and replace the Hitachi unit with a Weber and it runs better, has more power, and gets better fuel economy.
Wish I could have afforded a Weber, would have made things a LOT easier!! I had a heck of a time finding any good information on how to properly "tune" these smaller carbs. Most instruction sets are for LARGE V-8 carbs. All I could find for a small carb was that you have to "fiddle with the set screws until you got good results." Well, I wasn't getting any results one would call good. Oddly enough, I stumbled upon a video from the Philippines (in Tagalog) that showed exactly how to do it. Copied the video step-by-step and it tuned up perfectly!!
@@Peaphrey got a link to that cause I'm having the same problem with my rust bucket of a courier
@@Peaphrey you got the link? Thank you
What is that missing part that mounts to the side of the carb? with the 3-bolt patern, inlet in the middle, to the left of the choke diaphragm