BIG fuel leak!

[rcam97]

I have a 1977 mercury 85 hp inline 4 cylinder. This engine has 2 carbs and I just put in new floats, needles and seats in both of them. The problem is that the bottom carb is pouring out gas into the air box when running. What could be causing this? Any advice is much appreciated.

Thanks

 

[j_martin]

Re: BIG fuel leak!

I have a 1977 mercury 85 hp inline 4 cylinder. This engine has 2 carbs and I just put in new floats, needles and seats in both of them. The problem is that the bottom carb is pouring out gas into the air box when running. What could be causing this? Any advice is much appreciated.

Thanks

If you walk up to something, and it's working, and you do something to it, and it now doesn't work.

It's what you did.

Float outa wack, gasket missing under the seat, damaged needle, you get the point.

 

[rcam97]

Re: BIG fuel leak!

The reason I replaced these parts was because of this fuel leak. So it is not likely that I did something to cause this leak since it was leaking this way the day I got the engine.

 

[mike1245]

Re: BIG fuel leak!

going to have to pull it all apart again and recheck every thing all needles and needle seats also check cover to top of you float ( the one held in with 2 small bolts on side of carb ) make sure that if you hold it upside down the arms are level went through all this with mine last year

 

[coolguy147]

Re: BIG fuel leak!

set the needle height.

little bit above parrarel with the carbs so it will be less likely to leak out.

 

[ChrisfromVT]

Re: BIG fuel leak!

Did you clean out all the jets and re-seat them properly?
Float levers adjusted?

Maybe pull the carbs again and examine them side by side since one of them seems ok.
Does the motor fire up and idle?? If gas is pouring out, it;s a good bet that 3&4 aren't firing...

 

[j_martin]

Re: BIG fuel leak!

The reason I replaced these parts was because of this fuel leak. So it is not likely that I did something to cause this leak since it was leaking this way the day I got the engine.

Flip side of the addage. If you walk up to something, and it doesn't work, and you do something to it, and it still doesn't work, what you did didn't fix it.

When you go in to fix somebody elses bug, you have to go all the way down to bare castings, and check it out by the book. Something is missing, or broken from the other guy's tinkering.

My father in law had a Buick special that would kill, obviously starving for fuel. He had the carb rebuilt umpteen times, and it didn't fix it. It balked in my yard one day and I did a quick check and said, "I need to go through the carb." I had to buy the kit up front, promise not to hurt anything, and pay him 20 bucks to boot if I didn't fix it.

As I was tearing it down I pulled the main jets out. He said he'd watched this operation on this carb many times, and nobody ever pulled out the main jet. Well, under the main jet was a curl of brass turning that had been in there since factory new. That was the problem all along.

He took my family out to eat.

good luck
John

 

[Moody Blue]

Re: BIG fuel leak!

First question would be did you perform the rebuilds according to factory spec? Float level setup is critical.

A common problem with those carbs is that the cast alum filter cover is easily cracked or broken if extreme care is not taken during assy. Its possible that the cover is cracked and fuel is being pumped out thru the crack.

 

[rcam97]

Re: BIG fuel leak!

Thank you all for the quick replies. I will pull it back apart tomorrow and check for these. Any more advice will be appreciated. I also read some where that if one of the reed petals is broken that compression could be blowing fuel back out, but the fuel is quickly draining out of the front of the carb, if it were compression it would blow out in more of a spray I would think. I have rebuilt carbs in the past but never on a two stroke so I don't know much about reed valves.

 

[j_martin]

Re: BIG fuel leak!

Thank you all for the quick replies. I will pull it back apart tomorrow and check for these. Any more advice will be appreciated. I also read some where that if one of the reed petals is broken that compression could be blowing fuel back out, but the fuel is quickly draining out of the front of the carb, if it were compression it would blow out in more of a spray I would think. I have rebuilt carbs in the past but never on a two stroke so I don't know much about reed valves.

The reed valves are right behind the carburetor. They allow air to flow into the crankcase, but not out through the carb. If you hold a piece of paper over the carb and crank it, it'll pulse against the carb. If the reeds are bad, it'll flap against the carb, and then away from it. It's very obvious.

That's not likely the problem. Broken, missing, or misadjusted parts in the carb is most likely.

Go for it. You got about 3000 supervisers here helping ya.
John

 

[rcam97]

Re: BIG fuel leak!

Thanks everyone for the help. I fixed it. The float level was slightly off, I must have bumped when I put the bowl on the carb and knocked it out of adjustment. So I reset the float level and gave it another good cleaning and she fired right up and ran strong. This engine will make a 15ft runabout move, and move quick.

Thanks again.

 

[Moody Blue]

Re: BIG fuel leak!

Thanks for posting back with the results. Glad you are good to go.