Help! Experts needed

JackSuarez

JackSuarez

New Member
Hey guys I'm new to this forum, but I'm in the process of completely restoring my 80' Cb750c. I've done every thing and now I'm down to the carbs and having problems. I thoroughly cleaned the carbs, dipped in pinesol removed float bowls and everything to clean them by hand, etc. I even re-did all the O-rings. Now before I put the carbs back on the bike I wanted to test out the fuel. I hooked up a fuel line to the carbs and poured about half a Gatorade bottle full of gas. The problem is that the carbs aren't holding any gas. It's just going straight in and straight out through the overflows. I inspected the float and the float needle and they look fine. I don't know what else could be the issue.
 
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Could be the float level is too high.

you can also turn them upside down then blow in the fuel line . . if you can easily blow air, the needles are bad even if they look good.

if the needles are old and hard as a rock, they are bad.
 
What did you set the floats at? did you not blow test each needle and seat while you had them in your hands? not all needles are plastic or rubber tiped, some are aluminum, steel and brass... depends where they came from... toss the floats (all of them) in a bowl of water and see if any are lower than others after a few minutes, you could use gas too but don't smoke around it :eek: lastly were the floats nice and loose/free floating, the pins are not binding or anything right?

Do yourself a favor and search for the float level gauge (cardboard usually) or make one with a caliper and card stock, get them set to spec dead nuts.
 
Tune-A-Fish said:
What did you set the floats at? did you not blow test each needle and seat while you had them in your hands? not all needles are plastic or rubber tiped, some are aluminum, steel and brass... depends where they came from... toss the floats (all of them) in a bowl of water and see if any are lower than others after a few minutes, you could use gas too but don't smoke around it :eek: lastly were the floats nice and loose/free floating, the pins are not binding or anything right?

Do yourself a favor and search for the float level gauge (cardboard usually) or make one with a caliper and card stock, get them set to spec dead nuts.
Click to expand...

Well I turned the whole rack of carbs upside down and blew through and it barely if not at all let me pass air. All the floats stay/float on top of the water at the same level and are above the water line. The needles are all rubber tipped and the springs on them move freely. The floats moved without any restriction when they are on the carbs. And my carbs unfortunately do not have an adjustable float. My year carbs don't have that feature. I'm going to attach a video so you can see what is going on and have a visual.
http://youtu.be/b5YLzJNTXHI
 
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ok, most excellent.

there is a drain screw on the bottom of the bowl . . open it on the left carb . . if gas drains out, it is working.

tun carbs upside down

remove left float bowl and the one next to it.

if the float levels are the same, swap the needles then reassemble and try again.

the the outer one leaks and the one next to it does not, you know its your needles.

if your needles are not rubber, swap the brass seat too.
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barnett468 said:
there is a drain screw on the bottom of the bowl . . open it on the left carb . . if gas drains out, it is working.

remove left float bowl and the one next to it.

if the float levels are the same, swap the needles then reassemble and try again.

the the outer one leaks and the one next to it does not, you know its your needles.
Click to expand...

Oooo that's a brilliant idea thank you I will try that and update you all.
 
Plastic floats eh... well you need to get new needle & seat sets or score a set of donor carbs with carbon floats, I happen to have the floats and possibly needle & seats if you want to make the swap.
 
Tune-A-Fish said:
Plastic floats eh... well you need to get new needle & seat sets or score a set of donor carbs with carbon floats, I happen to have the floats and possibly needle & seats if you want to make the swap.
Click to expand...

Haha yea man they suck, and well how much you lookin' to give them for?

barnett468 said:
xlnt...yeah there are more then one way to skin a cat.

i like your test set up.
Click to expand...

Thank you brother and by the way I did the test this morning and the first carb was working, I opened the drain plug and behold, gas came out without just going through. You were right Im going to get new float needles. Freakin carbs lol
 
JackSuarez said:
Thank you brother and by the way I did the test this morning and the first carb was working, I opened the drain plug and behold, gas came out without just going through. You were right Im going to get new float needles. Freakin carbs lol
Click to expand...

xlnt, glad it worked . . its an easy deal now.
 
Ok guys well I'm back because today is when I received my new float needles. So here's what's happening now. I replaced all float needles, however if you all remember in the video I posted, only the first carb was working correctly. So I took the liberty to find out if it was just a bad float on the other ones and switched the float and needle from the 1st carb with the float and needle from the 3rd carb. I triple checked and made sure the floats go up and down smoothly. So after I put the float bowls back on, I went to go test it again with the gas hooked up. To my surprise the same thing was happening as before as if I never switched the needles and floats. Carb 1 was working perfectly with the float and needle from carb 3 and Carbs 2,3, and 4 were still overflowing! Now I'm clueless once again. Now I know it's not the float or float needles. What else could it be now?
 
only jumping in , have not read complete thread , but have you checked the bowl vents that equalise pressure to atmosphere. some carbs have a small pipe on them but almost all are brass and on the side of the carbie. blast some carb cleaner throughout these jets or aerostart(start ya bastard as it is known in australia). if these are blocked you might get this problem
 
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