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Offline maliveline

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Float bowls over flowing
« on: January 10, 2011, 05:36:53 PM »
Ok so today I started my bike to warm it up because I was going to ride it to work. All of the sudden I noticed my bike was leaking gasoline about 1 drop every second out of these 2 small hoses that come out of the bottom of my bike almost directly in the center of the bike. The hoses were about 1/4" in diameter and I can upload some pictures of them tomorrow if need be.

As my bike started to warm up it seemed like the gasoline stop dripping out of these hoses so I was think ok thats a good thing....
Then I walked around to the other side of my bike and then I noticed that there was gasoline dripping out of the bottom of my black air filter housing about 1 drop every second.
my bike died around the same time and I couldn't get it started up again.

does anybody think they could diagnose my problem from this information? Tomorrow I guess I'm planning on pulling the air filter housing off and have a look around to see whats going on.
But if you guys could offer me some advice it would help a huge amount.

oh and by the way I have a 1976 cb750a if you guys wanted to know.

-paul
« Last Edit: January 18, 2011, 12:48:30 PM by maliveline »
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Offline Gordon

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Re: Leaking Gasoline
« Reply #1 on: January 10, 2011, 06:18:26 PM »
Those hoses are connected to the overflow standpipes on the bottom of the float bowls on the carbs.  Gas leaking out of them means one or more of the float valves in the carbs isn't closing.  The most common cause of this is a sticking float.  Tap the float bowls with the handle of a screwdriver to unstick it.  There are other possible causes, but try that first and if it doesn't work then start looking deeper. 

Gas dripping out of the air filter housing can happen when the overflow pipes can't keep up with the flow of gas into the bowls, so it overflows into the air box and possibly into the engine.  If your oil smells like gas you need to change it.  If the air filter is wet you'll need to change that, too. 

Out of curiosity, has the bike been sitting unused for a couple of weeks or more? 
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Offline maliveline

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Re: Leaking Gasoline
« Reply #2 on: January 10, 2011, 06:29:28 PM »
well the bike is old obviously. I bought it about a little less that 2 months ago. since then I have riden it when I can but its winter and I live in oregon and I dont ride in the rain so on average I have rode the bike at least once or twice a week. with all that said the bike has never really ran great. A lot of times when I'm riding the bike it hesitates when I accelerate. It only has 10,XXX miles on it so it has obviously sat for quite sometime in its life span. its anyone's guess what kind of treatment this bike has had over the years but I am treating it like a baby now.

There is also some rust in the gas tank. and I'm sure the fuel filter probably needs to be changed. that was basically my next order of business. I just got done rebuilding the front break caliper.
« Last Edit: January 10, 2011, 06:34:13 PM by maliveline »
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Offline TwoTired

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Re: Leaking Gasoline
« Reply #3 on: January 10, 2011, 06:38:13 PM »
Just to add to what Gordon stated...
There s/b four drain hoses at the bottom, one for each carb.  Stuck float valves or sediment in the carbs will block the float valves open.  If those drain tubes are blocked by insect nests, then an overflowing carb drains into the air filter box or into the engine cylinders where it ends up in the oil supply, diluting it.

Check your oil.  If it has suddenly gotten too full, it is probably gas and you will need to change the oil.

Check your gas tank for rust.  Check your gas filter for tears.  Check your carbs for collected sediment.  And, make certain those drain tubes are clear.

Cheers,
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Offline Roach

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Re: Leaking Gasoline
« Reply #4 on: January 10, 2011, 06:57:33 PM »
check that your fuel is shut off when your not using your bike
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Offline Duke McDukiedook

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Re: Leaking Gasoline
« Reply #5 on: January 10, 2011, 07:10:47 PM »
Check to make sure your tubes in the bowl are not cracked either.
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Offline Gordon

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Re: Leaking Gasoline
« Reply #6 on: January 10, 2011, 07:21:06 PM »
Quote from: maliveline on January 10, 2011, 06:29:28 PM
well the bike is old obviously. I bought it about a little less that 2 months ago. since then I have riden it when I can but its winter and I live in oregon and I dont ride in the rain so on average I have rode the bike at least once or twice a week. with all that said the bike has never really ran great. A lot of times when I'm riding the bike it hesitates when I accelerate. It only has 10,XXX miles on it so it has obviously sat for quite sometime in its life span. its anyone's guess what kind of treatment this bike has had over the years but I am treating it like a baby now.

There is also some rust in the gas tank. and I'm sure the fuel filter probably needs to be changed. that was basically my next order of business. I just got done rebuilding the front break caliper.

So it sounds like this instance of overflowing could be just one of many symptoms to come of an old, neglected bike that need a thorough going-over.  If you haven't already, at the bare minimum it needs a full tune-up, as well as a fuel-system cleaning starting at the tank and working your way all the down through the carbs.   
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Offline maliveline

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Re: Leaking Gasoline
« Reply #7 on: January 11, 2011, 09:35:15 PM »
do these bike come stock with a fuel filter? I looked around on my bike and I dont see one anywhere. I also looking in my clymer shop manual for the procedure on changing a fuel filter and there is nothing in that book.

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Offline Roach

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Re: Leaking Gasoline
« Reply #8 on: January 11, 2011, 09:36:20 PM »
nope didnt have one ! ;)
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Offline maliveline

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Re: Leaking Gasoline
« Reply #9 on: January 11, 2011, 10:00:54 PM »
thanks. I decided I'm going to clean the rust out of my gas tank for my first step. I will post some pics in the following weeks and ask for more direction when I have finished that.

-cheers
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Offline Leanier

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Re: Leaking Gasoline
« Reply #10 on: January 11, 2011, 10:13:52 PM »
There ususually is a screen either in the petcock bowl, or on the straw part of it in the tank. (not sure what the 76 has, im sure someone else would know).  So it'll be worth taking the petcock off of your tank and making sure that its clean as well while your at it.
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Offline TwoTired

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Re: Leaking Gasoline
« Reply #11 on: January 11, 2011, 10:15:16 PM »
Quote from: maliveline on January 11, 2011, 09:35:15 PM
do these bike come stock with a fuel filter? I looked around on my bike and I dont see one anywhere. I also looking in my clymer shop manual for the procedure on changing a fuel filter and there is nothing in that book.

All Honda SOHC4s came with a fuel filter in stock form.  
The fuel filter is on top of the tank valve, unless someone removed it.

The clymer is a POS.

This parts list calls it a strainer; item #3
http://www.cmsnl.com/honda-cb750a-750-hondamatic-1976-usa_model487/partslist/F++12.html
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Lloyd... (SOHC4 #11 Original Mail List)
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Offline Roach

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Re: Leaking Gasoline
« Reply #12 on: January 11, 2011, 10:22:59 PM »
was thinking that he had one of those in line one below the petcock before the carbs. my bad for miss information
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Offline Cbowers

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Re: Leaking Gasoline
« Reply #13 on: January 12, 2011, 03:11:35 AM »
Had the same issue with my bike, I'm sure the needle and seats are worn on mine. What was causing my leak was the two bolts that hold the petcock/bowl on were missing the washers to seal around them. So even with the petcock off fuel was leaking through it. This was my fault because I took off my tank to paint it and did not replace them (I don't think they were there to start with). It would be worth replacing all the gaskets in the petcock.
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Offline Mark M

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Re: Leaking Gasoline
« Reply #14 on: January 12, 2011, 12:09:39 PM »
Wear is not always a big problem with float valves - if the parts are undisturbed they can wear together without any real loss of function.
The problems come when carbs get stripped and parts moved and swapped about, resulting in a missmatch of warn old parts.
Sometime less is so much more.
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Offline maliveline

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Re: Float bowls over flowing
« Reply #15 on: January 18, 2011, 01:03:18 PM »
I'm at war with my fuel system now. Here's some before pictures. I'm going to get the rust out of my gas tank tonight using electrolysis.
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Offline flybox1

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Re: Float bowls over flowing
« Reply #16 on: January 18, 2011, 01:12:26 PM »
give it "The Works" treatment first.  ;)
http://www.theworkscleans.com/toiletcleaner.html

search will get many a thread about it....
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Offline Duke McDukiedook

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Re: Float bowls over flowing
« Reply #17 on: January 18, 2011, 01:42:50 PM »
Or the vinegar treatment for a little less toxic cleaning.
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Offline faux fiddy

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Re: Float bowls over flowing
« Reply #18 on: January 18, 2011, 04:28:41 PM »
Quote from: Industrial-sized Dukiedook on January 18, 2011, 01:42:50 PM
Or the vinegar treatment for a little less toxic cleaning.


Search 'molasses.'  you'll find a thread saying it cleans up pretty well.
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