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post #1 of 25 Old 11-22-2016, 11:57 AM Thread Starter
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Leaking carburetor gasket - Um, help

So to start off, as several members already know my knowledge is limited and I ask A LOT of questions...
How bad if an idea is to use a very very small bead of RTV on a carburetor? The reason I ask and the history is:

Last fall I rebuilt the Marvel carb that is on my CCKA. After the rebuilt it had a slight fuel leak at the gasket between the body and top; before the rebuilt there was no leak. The amount of leakage at that time would be after I mowed for a couple hours there would be a dust ring at the gasket edge. Since the engine ran good I didn't give it a second thought; until now. Now the leak has gotten worse, after mowing the same amount of time the carburetor is covered in dust. Also the engine is not running as well as it used to and doesn't start very easily. I have tried to re-tune the carb, but when I tune it at full throttle with the mower deck running the engine doesn't run worth a darn at low throttle and no load; unless I give it some choke.

I have taken the carburetor apart and cleaned everything, there were no sign of "foo" anywhere and when I looked at the gasket for the body/top it looked OK; I can see where it was smashed when assembled.

My thought is to put a very small bead of RTV on the edge of the body and top and reassemble as normal; so it would be body - RTV - gasket - RTV - top. If there is a better way, I'm more than open to give it a try! Also thank you to everyone for looking at my thread and any suggestions.

Scott

Never argue with an idiot, they'll just drag you down to their level and beat you with experience.

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post #2 of 25 Old 11-22-2016, 12:28 PM
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Re: Leaking carburetor gasket - Um, help

I think you have a leaky needle or a float height issue. Excessive fuel height in the bowl will cause an overly rich condition that carb adjustments will not resolve.

Do not use RTV. RTV is not rated for gasoline. If the gasket is damaged where there are bits of paper missing then replace the gasket. If the gasket is intact, it can be reused without issue.

Onanparts.com or Boomer has new gaskets.

Code:
                              Current Inventory
   24G (Onan 24hp)    24GLX - was 16G  (Onan 24hp)   8249 - was 8129 (Onan 24hp)
        818T (Onan 18hp B48)       8163T - was 8123 (Onan CCKA) 
                              8183T (Onan B48)
   5665 w/brakes        5665        5660        Pro-8         Pro-16 w/brakes

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post #3 of 25 Old 11-22-2016, 12:39 PM Thread Starter
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Re: Leaking carburetor gasket - Um, help

Thanks for the reply Richard. I have checked the float height and it's good, the gasket looks brand new. How would I tell/fix a leaky needle?

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post #4 of 25 Old 11-22-2016, 01:08 PM
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Re: Leaking carburetor gasket - Um, help

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Originally Posted by mcsquish View Post
Thanks for the reply Richard. I have checked the float height and it's good, the gasket looks brand new. How would I tell/fix a leaky needle?
With a new needle or clean any gunk in the seat.

The other possibility is that the float itself is bad. There are aftermarket ones, but the last I checked, they don't last more than about 6 months. Genuine Onan floats are insanely priced.

If it was mine, I would call Boomer and see what a good used B48 carb costs.

rich

Code:
                              Current Inventory
   24G (Onan 24hp)    24GLX - was 16G  (Onan 24hp)   8249 - was 8129 (Onan 24hp)
        818T (Onan 18hp B48)       8163T - was 8123 (Onan CCKA) 
                              8183T (Onan B48)
   5665 w/brakes        5665        5660        Pro-8         Pro-16 w/brakes

For Gravely Manuals and more visit http://GTCOA.com
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post #5 of 25 Old 11-22-2016, 01:13 PM Thread Starter
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Re: Leaking carburetor gasket - Um, help

Thanks again for the help! I think I'll go through it again and make sure the float doesn't have a leak and inspect the needle closer. If that doesn't help I'll check with Boomer.

Never argue with an idiot, they'll just drag you down to their level and beat you with experience.

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post #6 of 25 Old 11-22-2016, 04:25 PM
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Re: Leaking carburetor gasket - Um, help

one of the floats in my Marvel carb had a pin hole so gas had gotten in and caused it to sink. Make sure to shake the float. You can hear the gas in it if there is any.
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post #7 of 25 Old 11-22-2016, 04:30 PM
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Re: Leaking carburetor gasket - Um, help

mcsquish,
After you investigate the possible culprits AND if you you still find yourself needing a sealant for the carburetor, go to your local auto parts store, Walmart, or even Dollar General and get a tube of 'Seal-All'. It is relatively inexpensive $3 to $4 a tube. It is "chemical resistant; it is not affected by oil, gasoline, alcohol, and most solvents". I have successfully used this product on my Honda Rancher's carburetor with no leakage whatsoever! - this repair was made 18 months ago and has not leaked a drop since. I searched long and hard to find an inexpensive sealant that works in this environment and came across this product.

Daryl G

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post #8 of 25 Old 11-22-2016, 07:09 PM
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Re: Leaking carburetor gasket - Um, help

scott and club
some thoughts here.
during the rebuild was a new needle and seat installed?
if so, was the needle the later model with a viton tip?
also, if the gasket for the seat did not get replaced,
or tightened properly that will cause a leak
even if the needle is seated properly in the seat.
thank you. boomer
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post #9 of 25 Old 11-22-2016, 08:05 PM
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Re: Leaking carburetor gasket - Um, help

Quote:
Originally Posted by Greg in WV View Post
one of the floats in my Marvel carb had a pin hole so gas had gotten in and caused it to sink. Make sure to shake the float. You can hear the gas in it if there is any.
Find the hole and solder it up and it will work again.

Code:
                              Current Inventory
   24G (Onan 24hp)    24GLX - was 16G  (Onan 24hp)   8249 - was 8129 (Onan 24hp)
        818T (Onan 18hp B48)       8163T - was 8123 (Onan CCKA) 
                              8183T (Onan B48)
   5665 w/brakes        5665        5660        Pro-8         Pro-16 w/brakes

For Gravely Manuals and more visit http://GTCOA.com
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post #10 of 25 Old 11-23-2016, 08:07 PM
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Re: Leaking carburetor gasket - Um, help

Well, that would have been the smart thing to do. Nobody ever accused me to being very smart! I ended up breaking it and having to replace it. The good news is that the replacement appears to work fine.
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post #11 of 25 Old 11-23-2016, 08:30 PM
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Re: Leaking carburetor gasket - Um, help

I had one that leaked and I actually had to solder it up while most of it was immersed in cold water.

Tricky but doable.

Code:
                              Current Inventory
   24G (Onan 24hp)    24GLX - was 16G  (Onan 24hp)   8249 - was 8129 (Onan 24hp)
        818T (Onan 18hp B48)       8163T - was 8123 (Onan CCKA) 
                              8183T (Onan B48)
   5665 w/brakes        5665        5660        Pro-8         Pro-16 w/brakes

For Gravely Manuals and more visit http://GTCOA.com
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post #12 of 25 Old 11-29-2016, 03:57 PM Thread Starter
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Re: Leaking carburetor gasket - Um, help

For a quick update on the fun... The float is good, there is not a leak, and I rechecked the setting.

Boomer, when you say "new needle and seat" what are you referring to; is it the idle needle, the main needle or the "thingy" (a highly technical term since I don't know the real name) that the float controls? If it is the float "thingy" I did not change it when I did the rebuild because I could get the brass piece that screws into the carb loose and I didn't want to destroy it. Yesterday I picked up a rebuild kit that has this part along with the "thingy" and new gaskets. This kit is different than the one I used before, it has more parts and gaskets, it actually has two housing gaskets and I'm not sure why it does. I'm hoping to tear down the carb tonight so it can soak overnight.

Thank you everyone for the help. I would have a nasty mess with out it.
Scott

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post #13 of 25 Old 11-30-2016, 03:51 AM
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Re: Leaking carburetor gasket - Um, help

Quote:
Originally Posted by mcsquish View Post
For a quick update on the fun... The float is good, there is not a leak, and I rechecked the setting.

Boomer, when you say "new needle and seat" what are you referring to; is it the idle needle, the main needle or the "thingy" (a highly technical term since I don't know the real name) that the float controls? If it is the float "thingy" I did not change it when I did the rebuild because I could get the brass piece that screws into the carb loose and I didn't want to destroy it. Yesterday I picked up a rebuild kit that has this part along with the "thingy" and new gaskets. This kit is different than the one I used before, it has more parts and gaskets, it actually has two housing gaskets and I'm not sure why it does. I'm hoping to tear down the carb tonight so it can soak overnight.

Thank you everyone for the help. I would have a nasty mess with out it.
Scott
Thats the kit I have, like a 29 or so piece kit w/2 gaskets for two diff carbs. One of the "thingy's" you speak of might be that *** tiny little curly q spring that actually goes under the float, there is a pic of it I posted in the picture thread and Im pointing to it with the point of a knife about two months ago, its easy to find, the pic that is. I was gonna reccomend trying to re-surface the meeting slabs of the carb (that gasket goes in between) just incase one side or both sides somehow got warped. A carefull resurfaceing, like one or two light passes over some fine sand paper secured flat on a hard surface. (15 mins later) OK I found my carb-kit pics if you think it might be helpfull to you to look at them, on top of this page it says "1 of 369", so go to page 12 ( on 7-10-16) and the thread I started is called "Carb Questions-squiggly looking piece" and the pics of my kit are there on first page. I was bored anyway, waiting to get tired lol.

Last edited by Gerrard; 11-30-2016 at 04:17 AM.
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post #14 of 25 Old 11-30-2016, 10:37 AM Thread Starter
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Re: Leaking carburetor gasket - Um, help

Gerrard, well thank you I guess for being board and not being tired... I feel your pain. I found your photo and my carb (it's a "VD" model) does not use the spring, but what I am calling a "thingy" is the part that the spring mates to. Thank you for the sandpaper idea, I was thinking about doing something but using fine sandpaper sounds way better than what I was thinking... lol

I have the carb torn down and soaking in solvent tank here at work so hopefully I'll be putting it back together tonight.

Never argue with an idiot, they'll just drag you down to their level and beat you with experience.

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post #15 of 25 Old 11-30-2016, 01:27 PM
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Re: Leaking carburetor gasket - Um, help

It sounds like you are referring to the needle valve. I have the DD carburetor. The brass seat for the needle valve was pretty easy to get out on mine, but I realize that doesn't mean much. I used the widest flat head screwdriver I could find. Like many others here, I strongly suggest blowing out the passages before putting things back together. I would replace as many pieces as possible from the kit. The big help for me was replacing the idle jet screw. My old one was in awful shape and the new one made it run much better. I have read in other posts that people have had success leveling carburetor surfaces using sandpaper on a flat surface, but I have never tried it.

Good luck!
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