Author Topic: No Fuel Out Of Carb #1 or #3 ??  (Read 1062 times)

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Offline JBW5

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No Fuel Out Of Carb #1 or #3 ??
« on: April 06, 2013, 11:08:07 PM »
After pulling apart and cleaning my 1978 cb750K carburetors I only am able to eject fuel out of carburetors #2 and #4. The bowls are filling up and everything however no fuel is squirting out of carburetors #1 or #3. I first thought float height so I took off the bowls and set it but the results were the same...any help would be much appreciated! HAPPY BIKING! Thanks 
1978 CB750K

Offline harisuluv

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Re: No Fuel Out Of Carb #1 or #3 ??
« Reply #1 on: April 06, 2013, 11:34:41 PM »
When you say "ejecting" and " squirting" it seems like you are talking about the accelerator pump nozzles, is that what you mean?  Or are you not firing on those cylinders?

Offline JBW5

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Re: No Fuel Out Of Carb #1 or #3 ??
« Reply #2 on: April 07, 2013, 09:54:52 AM »
Yes that is what im talking about. Once i put them together i set them on the bench, filled them with fuel through a funnel and then twisted the throttle linkage with my hand and only numbers 2 and 4 squirt though the accelerator nozzle. Could this nozzle be plugged? If so How do I clean it? It seems near impossible to get to. Another guy told me that it could be a vacuum issue but without being on the bike i don't see how this cold be true? Thanks for any help!
1978 CB750K

Offline lucky

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Re: No Fuel Out Of Carb #1 or #3 ??
« Reply #3 on: April 07, 2013, 03:26:18 PM »
There are three black rubber tubes feeding the accelerator squirt nozzles.
Remove each one and squirt some carb clean into the hole where you took off the tube and it should clean out the nozzle. Also there is two small pieces of brass tubing in each hose. Do not throw those away if you replace the fuel line for some reason.


Protect your eyes!!!

The good news is your pump diaphram is working!

Click on the photo below to enlarge.
« Last Edit: April 07, 2013, 03:28:41 PM by lucky »

Offline JBW5

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Re: No Fuel Out Of Carb #1 or #3 ??
« Reply #4 on: April 07, 2013, 07:55:18 PM »
Thanks! I did what you said but cant seem to get the carb fluid to spray through #1 and #3. This tells me they are most certainly clogged... Is there another methd for clearing these little guys? Thanks once again!
1978 CB750K

Offline pscycle927

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Re: No Fuel Out Of Carb #1 or #3 ??
« Reply #5 on: April 08, 2013, 12:08:11 AM »
I bought a big syringe at the local feed store for giving horses shots  and put it over the little hole then wrapped a wet  cotton ball around the tip and plungered the piss out of it until they all broke free and squirted carb cleaner.it took a few minutes of plunging and pulling but it worked good to break loose the crud in the nozzles.

Offline JBW5

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Re: No Fuel Out Of Carb #1 or #3 ??
« Reply #6 on: April 08, 2013, 06:16:37 AM »
Ok that an idea! Do you mean you slid the whole needle down over the nozzle then just pumped air back and forth through it?
1978 CB750K

Offline Duke McDukiedook

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Re: No Fuel Out Of Carb #1 or #3 ??
« Reply #7 on: April 08, 2013, 07:59:15 AM »
You need to take apart those jets and clean them with wires, carb cleaner and compressed air through all orifices.
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Offline JBW5

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Re: No Fuel Out Of Carb #1 or #3 ??
« Reply #8 on: April 08, 2013, 08:35:50 AM »
I have cleaned the jets out, the nozzles are clogged.
1978 CB750K

Offline flybox1

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Re: No Fuel Out Of Carb #1 or #3 ??
« Reply #9 on: April 08, 2013, 09:22:25 AM »
i frayed some brass wire, and bent the end of one strand, like a hook, and stuck it in the nozzles to clear the debris.  kinda hard to see as the hole is on the other side of the nozzle.  poke around, spray carb cleaner, poke around some more...spray more.  just keep at it, you'll find it. 
'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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1974 550K0 (stock), 1973 CB350F (stock), 1983 Yamaha XS400K (POS)
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Offline neilc

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Re: No Fuel Out Of Carb #1 or #3 ??
« Reply #10 on: April 08, 2013, 03:17:39 PM »
why do my carbs have a looks like a jumper line instead of vent hoses in my pics,other pics of carbs posted on this topic have 2 vent lines