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Author Topic: carbs leaking out overflow tubes  (Read 3286 times)

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Offline MikeJW

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carbs leaking out overflow tubes
« on: July 31, 2010, 08:24:15 AM »
When I first got my cb750, 3 of the 4 carbs were constantly leaking gas from the overflow tubes even after I adjusted all the float heights. When I examined the little brass standpipes in strong sunlight, I saw that they were split almost from bottom to top...undoubtedly from some water being in them over a cold winter. I tried to pull them out of the bowls, but saw that I was going to damage them. I went to the local Hobby Lobby and purchased a package of brass tubing for a few dollars. The size is critical. I bought 5/32 in. OD. I cut pieces about 1 mm less than the exposed part of the standpipe in each bowl. I made sure there was no burr on the inside of the cut pieces and then tapped them down over the standpipes. It got a little tricky towards the very end because they fit so tightly. After the first one, I thought about cutting them a little longer and then trimming them later. I don't think it makes much difference as long as you don't end up with something longer than the original. It is very important, however, that you have a nice square cut on the bottom end and you drive it down all the way. In my case, they fit so tightly that I never had to do another thing. I never had another drop leak out and I believe they will last the life of the bike...especially if I make sure to drain all the gas out of the carbs when freezing weather comes in the winter. Really an easy fix.
1972 CB750K2

Offline last_cb750

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Re: carbs leaking out overflow tubes
« Reply #1 on: July 31, 2010, 03:42:30 PM »
what year/model bike?
78 CB750K
75 CB750K (sold)

Offline MikeJW

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Re: carbs leaking out overflow tubes
« Reply #2 on: July 31, 2010, 04:41:53 PM »
1972 cb750 K2
1972 CB750K2

Offline dusterdude

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Re: carbs leaking out overflow tubes
« Reply #3 on: August 02, 2010, 04:20:10 PM »
ive been thinking about doing that to mine too,now i think i will
mark
1972 k1 750
1949 fl panhead
1994 converted 883 sportster
1998 cbr600 f3

Offline lucky

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Re: carbs leaking out overflow tubes
« Reply #4 on: September 15, 2011, 10:39:51 AM »
Very unusual problem thats for sure.

Offline Paul Lowe

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Re: carbs leaking out overflow tubes
« Reply #5 on: October 02, 2012, 04:38:05 AM »
neoprene tipped bowl float needles worked for me.
My Honda sickness deepens

CB350F 1972
CB360G 1974
CB750 K1 1971
CT90 K0 1968
C102 1963
C50 1968
C70 1972
C90 1974
CL90 1968

1/2HP electric bike home made...

Offline 6adan

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  • 70 CB750 JDM,75 GL1000,79 GL1000,79CBX, 95 GL1500
Re: carbs leaking out overflow tubes
« Reply #6 on: February 06, 2013, 06:57:23 PM »
You can also solder them. I have done it on my 70 and just had to do it on my CBX.

 

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