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Losing my small mind - 1969 85hp flooding issue

S

SteveInMN

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Runs super rich and eventually floods while idling. Requiring pulling the plugs, drying them, waiting a while and then eventually restarting. No one with me is impressed (in a positive way).
When you pump up the carbs (lots of pressure on the bulb) , the bottom carb holds, but the top one eventually pours gas out.
Been through several needles/seats, two floats, three gaskets -- no joy. Carb is immaculate. Nothing is sticking. Seat gaskets are good.

This should be simple. What. The. Hell. am I missing here? Maybe I'm chasing the wrong causation. Does one carb or the other just always flood if you squeeze the bulb hard enough?

TIA,
Steve
 
How hard are you mashing on the bulb? Squeeze it enough to fill the carbs for starting, and leave it alone.

But it should not be flooding out while running, anyway.

A ruptured fuel pump diaphragm will flood one cylinder.
 
fdrgator said:
How hard are you mashing on the bulb? Squeeze it enough to fill the carbs for starting, and leave it alone.

But it should not be flooding out while running, anyway.

A ruptured fuel pump diaphragm will flood one cylinder.
Click to expand...
Right, I would not ordinarily pump that hard - but I'm trying to figure out which carb is admitting too much fuel. The bottom one seals tight after filling, the top one sez "Come on in!". But- given enough pressure, maybe that's normal? Dunno.
 
Most carburetor " issues " turn out to be something else.-----Post the compression values here.--Distributor cap cleaned ?-----Breaker points set at 0.010" ?--Does spark jump a gap of 3/8" on all leads?----Thermostat working?------Low speed mixture needles set correctly?
 
SteveInMN said:
Right, I would not ordinarily pump that hard - but I'm trying to figure out which carb is admitting too much fuel. The bottom one sels tight after filling, the top one sez "Come on in!". But- given enought pressure, maybe that's normal? Dunno.
Click to expand...

racerone said:
Most carburetor " issues " turn out to be something else.-----Post the compression values here.--Distributor cap cleaned ?-----Breaker points set at 0.010" ?--Does spark jump a gap of 3/8" on all leads?----Thermostat working?------Low speed mixture needles set correctly?
Click to expand...
 
  • Compression: 105#, each cylinder. Probably a bit better, since this was without the throttle wide open (I forgot that part)
  • Distributor cap: Wasn't visibly dirty, but was wiped clean anyway during the major go-through this past winter.
  • Breaker points: Set @ 0.010" and cleaned (dirty points initially kept this project form starting)
  • Spark gap jump: No idea. Light comes on on all four with an in-line zenon tester
  • Thermostat: Vernatherm tested, throws 6mm @ 175deg F.
  • Low speed needles: 7/8 of a turn out from just seated, per the factory manual. I have not gone through the manuals fine-tuning process - as I thought that was for fine tuning, not a gross problem like flooding. But maybe this is it?
It starts right up and runs like a champ - except at protracted idle (lots of slow channels on my lake), when it loads up, shakes like a rodeo bull, and eventually dies, reeking of fuel, requiring plugs be pulled, dried, a twenty minute wait and then she starts right up. Also, the lower carb seals up, but the upper pours fuel when I squeeze the bulb. This all looks like flooding. Now, I always appreciate me some good out-of-the box thinking, but docs are trained to not look for zebras when a horse is standing right there.

Once I have
  • a good valve,
  • a good gasket seal on the fuel channel between the (aluminum) bowl and the body, and
  • a good (tested in hot water for bubbles) float
- what could be causing that upper carb to pour fuel? Or is it normal for one carb or the other to pour fuel? Maybe I have just got unlucky and two new needle valve/seat sets were bad?

TIA,
Steve
 
Ok, I swapped the needle valves and seats and floats from the top to the bottom carb and lo and behold, now the bottom carb leaks. So it must be a bad valve or a bad float after all, despite the recent replacements. I have OEM NOS ones on order and will revert once they are in and installed.
 
I rebuilt my carbs on my '99 Yamaha 115 a few weeks ago. When installed and pumped the primer, I had the same problem. Took them off and took them apart and started looking around and saw where the new float needles that came in the kit I ordered were almost 1/8" shorter than the ones I took out. DON'T ORDER no-name, Chinese after market parts. OEM from now on for me.
 
Also, you can easily test the needle and seat by hooking a piece of hose up to the nipple where fuel enters the carb and blow in it. With the carb upright, you should hear air flowing into the carb. Slowly turn it upside down, and you should hear the flow of air stop as the float "drops" inside the bowl with the carb upside down. That's much easier that putting it all together only to find that there's a problem.
 
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