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Author Topic: Where the hell are my idle and mixture screws on my 78 cb750 carbs?  (Read 1691 times)

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Offline specialone70

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Where the hell are my idle and mixture screws on my 78 cb750 carbs?
« on: September 23, 2015, 06:30:44 PM »
I can't find them on my bike. I looked at pictures online and it seems previous years have really obvious screws but for some reason pictures of '78 carbs don't have the screws in the same spot. Sorry if I'm being stupid but I'm really confused. Thanks!
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Offline Mantree

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Re: Where the hell are my idle and mixture screws on my 78 cb750 carbs?
« Reply #1 on: September 23, 2015, 07:30:19 PM »
Can you give us photos so we know what we are working wih

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Offline specialone70

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Re: Where the hell are my idle and mixture screws on my 78 cb750 carbs?
« Reply #2 on: September 23, 2015, 08:24:31 PM »
Here's an image I found of the same carbs: http://img.photobucket.com/albums/v702/trailsforus/IMG_0857-1.jpg

Here's a picture of what the older ones (and the ones in my manual) look like. You can clearly see the idle and mix screws: http://honda-cb750-s.456789.n3.nabble.com/file/n4022423/1969-70-carbs.jpg
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Offline seanbarney41

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Re: Where the hell are my idle and mixture screws on my 78 cb750 carbs?
« Reply #3 on: September 23, 2015, 09:08:17 PM »
not much of use in that goofy pic...who is the dumbass that looped their float bowl drain hoses up to the adjacent carb?

Idle mixture is not visible in the pic, it is in front of the float bowl pointing up.  Idle speed screw is not visible either.  IIrc, it is on the the rack between carb 3 and 4...kinda hard to get at...
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Offline Mantree

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Re: Where the hell are my idle and mixture screws on my 78 cb750 carbs?
« Reply #4 on: September 23, 2015, 09:54:45 PM »
Quote from: seanbarney41 on September 23, 2015, 09:08:17 PM
not much of use in that goofy pic...who is the dumbass that looped their float bowl drain hoses up to the adjacent carb?

Idle mixture is not visible in the pic, it is in front of the float bowl pointing up.  Idle speed screw is not visible either.  IIrc, it is on the the rack between carb 3 and 4...kinda hard to get at...
Beat me to it they are post 76 carbs as for the idle mix screw when you tear them down grind off the little tab, all it dose is liners how far you can turn the screw with the float bowl on

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Offline flybox1

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Re: Where the hell are my idle and mixture screws on my 78 cb750 carbs?
« Reply #5 on: September 24, 2015, 06:50:54 AM »
bottom left of this picture
(the RED arrow is pointing to the pilot jet)
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'78 750K (F3 engine) PD42b's, Modified airbox w/K&N  filter, 40/110 jets, 1 needle shim, IMS@ 1 turn out. Kerker + Cone 18" QuietCore

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Offline BobbyR

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Re: Where the hell are my idle and mixture screws on my 78 cb750 carbs?
« Reply #6 on: September 24, 2015, 12:40:47 PM »
They are recessed back toward the head at the rear of the floatbowl. You can see the screw in the pic above.
Feel around with a cold engine. Be ready to burn your fingers when making the adjustment on a running motor. They are mixture screws not air screws found on early models.
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Offline specialone70

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Re: Where the hell are my idle and mixture screws on my 78 cb750 carbs?
« Reply #7 on: September 24, 2015, 10:23:49 PM »
Ok got it. Thanks a bunch, guys. This forum never lets me down!
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