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Author Topic: sucking fuel through mains at idle??  (Read 603 times)

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Offline anchorweight550

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sucking fuel through mains at idle??
« on: September 12, 2010, 03:22:33 AM »
Ok so I read through Simon's post about his "idle hover" and Ive been beating myself up trying to figure out what the deal is with my bike. Im having the same sort of problems. Bike is a 74 cb550 with the pd46c carbs and intake runners. My plugs are RICH at idle my floats set to 14.5 (12.5 was too high I felt) when my bike warms up the revs hang and when I adjust the idle screw the bike will not idle. Tried syncing them, but still doesnt want to run right. One thing I have noticed in the past is whenever I messed with my needle height, the idle would change accordingly. Thinking about dropping the needle and seeing what that does. Anybody have a similar story?
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Offline Terry in Australia

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Re: sucking fuel through mains at idle??
« Reply #1 on: September 12, 2010, 03:46:44 AM »
That's unusual mate, your main jet/needle changes shouldn't affect your idle RPM or mixture. Are you sure your idle jet and idle circuit isn't blocked? Cheers, Terry. ;D
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Offline anchorweight550

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Re: sucking fuel through mains at idle??
« Reply #2 on: September 12, 2010, 04:14:03 AM »
I couldnt be more sure, my troubleshooting has officially made me the master of carb dissasembly
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Offline Retro Rocket

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Re: sucking fuel through mains at idle??
« Reply #3 on: September 12, 2010, 04:18:34 AM »
Quote from: anchorweight550 on September 12, 2010, 04:14:03 AM
I couldnt be more sure, my troubleshooting has officially made me the master of carb dissasembly

Ahhhhhh....there's the problem, you just have to master the assembly and you'll be fine..... ;D ;D ;D

Couldn't resist.... ;)

Mick
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Offline Bodi

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Re: sucking fuel through mains at idle??
« Reply #4 on: September 12, 2010, 07:53:16 AM »
The slide cutout is there to eliminate false choking - sucking fuel through the main at very low slide opening. Without the cutout the venturi point moves from around the middle of the slide to the leading edge of the slide. At idle, the needle jet should be in an area of roughly atmospheric pressure not at vacuum. I am surprised that you're getting much flow through the needle jet at idle. Are your slides in the right way around? If they are I think checking for any clogs in the idle circuit would be in order. Carefully check the emulsion tubes on the pilot jets, plugged emulsion tube holes will richen up your idle.
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