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guyom
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Question on Carb BING
08/06/18 at 11:03:04
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Hi Guys, i am just wondering if this is normal that carb leaking when the gaz line is on OFF ?

Indeed, one year ago i disassembled the carb and clean and change the seals... to solve a problem of choke (when choke is ON the motor cought and stop)

I recently changed the floating needles... both, but nothing changes... should i change also the floats ? you know prices of separate pieces increase the final bill and at the end, i think buying new carbs should be less expensive Wink

Thanks for time !
Guyom
  
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Matt Chapter
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Re: Question on Carb BING
Reply #1 - 08/06/18 at 11:27:04
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Definitely not normal, plus leaking carbs really reduce your gas mileage.  Floats are a good place to check, you can weigh them to see if they need to be replaced.  I can't remember if the manual states the correct weight ranges, but it's been posted here several times.  If the floats are good and set correctly there could be a blockage in the float needle.
  

'86 R65 with '84 motor ~66000 miles.  SS lines, Spiegler rotor, Progressive monoshock, Keihan silencers, a piece of Pichler fairing.
'76 CB400F ~26000 miles.  Weepy SS lines, big dent in the tank.
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guyom
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Re: Question on Carb BING
Reply #2 - 08/06/18 at 12:19:33
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thanks Matt. I remarked also another things : half of the time, when i ride and stop the idle is high.. and then go down (or not)... so i think there is some gaz somewhere that burning and then arrive to normal.

Question : do you let the small Float needle clip or i can remove them. They does not look good... and i m wondering if they can block the float needle at some point. 

TNX !
  
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georgesgiralt
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Re: Question on Carb BING
Reply #3 - 08/06/18 at 14:05:28
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Normal float weight without needle is 12.5 gr.
The rubber part of the needle should be spotless.
If the needles are ok but still leak you can ream a little the seats with the correct sized drill tap and gentle short motion.
Be careful, a new carburetor is _very_ pricey.
  
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Barry
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Re: Question on Carb BING
Reply #4 - 08/06/18 at 14:21:40
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The floats turn into sinkers at approx. 16 grams.

One simple test you can do is remove the idle mixture screw after first checking how many turns out it is so you can return it to the original setting.  If fuel drips out of the hole then that indicates a flooded idle circuit and a float that's close to a sinker or a bad float needle.  This test is useful even before the the carb becomes incontinent via the overflow.
  

Barry Cheshire, England 79 R45
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guyom
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Re: Question on Carb BING
Reply #5 - 08/07/18 at 08:06:40
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Hi Barry, many thanks for the advice so i just have to remove the mixture idle and check if fuel leaks right ?

I modified the float needle level yesterday and up to 100km/h... the motor makes some "RATATATAAAATAATATA" Wink meaning the fuel level is not enough in the carb i think.. so that could indicate that the float needle work better than the olders... i will do you test tonight.

Just a question : motor warms or cold ? motorcycle on the central stand ? and perfectly horizontal right ?
Thanks for time !

Guyom
  
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Barry
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Re: Question on Carb BING
Reply #6 - 08/07/18 at 11:23:05
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guyom wrote on 08/07/18 at 08:06:40:
ust a question : motor warms or cold ? motorcycle on the central stand ? and perfectly horizontal right ?
Thanks for time !


Warm or cold doesn't matter but fuel tap on and bike reasonably level on the centre stand.
  

Barry Cheshire, England 79 R45
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guyom
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Re: Question on Carb BING
Reply #7 - 08/09/18 at 08:23:30
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Hi Guys, so i want to give you updates after several attempts (unfortunately without success Sad)

so here is

Background : Overflow of the left carb never the right one. (both carb have been rebuilt perhaps a mistake somewhere but motor runs well (indeed as well as the carb can Wink) by rebuild i mean cleaning and seals changed.

So i decided to change the float needles = left Overflow, right good. = not the needles

So i decided to inverse the float (so right to left et so) = nothing change : left Overflow, right good… = not the floats

i tried Barry test : open the fuel line and remove the mixture idle : left a bit wet but no leak, right good.

So i changed all fuel filter… and clean again the left carb… nothing changes :

Left Overflow (i mean after 5 to 15 minutes depending the modification i did, the left carb leaks).

Right Good…

Any suggestions or i should by a correct left carb… i am out of ideas…

Thanks for time !!!
  
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georgesgiralt
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Re: Question on Carb BING
Reply #8 - 08/09/18 at 08:39:35
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Remove the leaking carb and inspect the sealing surface where the float plug goes.
Is there some sort of corrosion or default ?
Have you swapped the float needles too or just the floats ? Because if you swapped just the floats, maybe one needle is worn out ?
  
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guyom
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Re: Question on Carb BING
Reply #9 - 08/09/18 at 08:49:20
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hum i did not see corrosion but perhaps the line of the fuel inside.

No i did not swap the float needles, but both (left and right needles) are new and installed one week ago.
  
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guyom
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Re: Question on Carb BING
Reply #10 - 08/09/18 at 09:43:20
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but you are right = there is some scratches on the small metal rod that fix the floats... perhaps no good... will check.
  
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