Replacement for Flo Jet carb

sparkwizard

sparkwizard

#61
#61
We had one for pumping water a LOOONG time ago. It did not have a carburetor on it. It had a mixer that was like a straw in the intake that drew white gas from a little cup. In order to start it, we made sure the coil was disconnected. We took a rag soaked, dripping, with gas, and pushed it into the intake, turned the flywheel 4 full turns, removed the rag, connected the coil and spun the flywheel HARD. Sometimes we had to prime that beast a couple of times, but once it started, it was hard to stop. It did NOT have a throttle. It had a little centrifugal whirligig that controlled the intake valve. When it needed a boost of power,, it would allow the valve to close, causing the cylinder to pop, taking in a gulp of fuel and air and making the flywheel spin a tiny bit faster. Then the valve was held open and the engine freewheeled with no compression and no air coming through the mixer.
Hit and Miss meant just that. it ran about 700 RPM and it only "hit" when it slowed to about 675.
Hope this helps some of you youngsters.:rolleyes:

##EDIT## I think it held the exhaust valve open. I think the intake had no rocker, just a weak spring. It was sucked open by the piston descending when the exhaust valve was allowed to operate. When coasting, the exhaust was open and huffing.
Another interesting fact is that the cooling system is a large tank cast onto the cylinder. It has no lid, water is poured in and just evaporates as it runs.
 
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Minimichael

Minimichael

Well-Known Member
#63
#63
sparkwizard said:
We had one for pumping water a LOOONG time ago. It did not have a carburetor on it. It had a mixer that was like a straw in the intake that drew white gas from a little cup. In order to start it, we made sure the coil was disconnected. We took a rag soaked, dripping, with gas, and pushed it into the intake, turned the flywheel 4 full turns, removed the rag, connected the coil and spun the flywheel HARD. Sometimes we had to prime that beast a couple of times, but once it started, it was hard to stop. It did NOT have a throttle. It had a little centrifugal whirligig that controlled the intake valve. When it needed a boost of power,, it would allow the valve to close, causing the cylinder to pop, taking in a gulp of fuel and air and making the flywheel spin a tiny bit faster. Then the valve was held open and the engine freewheeled with no compression and no air coming through the mixer.
Hit and Miss meant just that. it ran about 700 RPM and it only "hit" when it slowed to about 675.
Hope this helps some of you youngsters.:rolleyes:
Click to expand...
It helped me. So much so that now I don't know how even the flow jet managed to feed that engine, especially with all the manifold elbowing.
 
sparkwizard

sparkwizard

#64
#64
They only have compression sometimes, otherwise, they freewheel with their huge flywheels. If it holds the intake valve open as it freewheels, it would be huffing air in and out of the carburetor.
 
G

Geo46

Member
#67
#67
Is it possible to change the main jet in this carb? GX 160 ? if so, would that let more fuel in? It did run at one time with the Flo Jet , however I never it, you are exactly right for their use for pumping water, very basic operation, nothing like a car engine.

Remember, this is all experimental at this point.
Thanks
 
G

Geo46

Member
#69
#69
Mixers are available, I am familiar with the mixers, I believe the carb gives better throttle control for our application, I may revisit the mixer again if a carb does not work.
Thanks
 
sparkwizard

sparkwizard

#70
#70
When it ran with the Flo jet carb on it, was there any type of throttle response? With a low compression engine and those huge flywheels, it would seem like you would either flood it or just bog really bad when you opened the throttle.
 
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Geo46

Member
#71
#71
Don’t know, never saw it run, my plan now is to spray a bit of gas into the throat of the carb and see what response I get from that I would hope to see gas in the cylinder and hopefully get a pop at least.
 
sparkwizard

sparkwizard

#72
#72
If you do not hold the intake valve open, does it open itself to let air and fuel in?
I think it should. Like I said before, we stuck a rag in the intake and spun it. I do not recall ever touching the valves while starting the beast.
 
G

Geo46

Member
#73
#73
Update, I stuffed a gas soaked piece of paper into the throat of the carb and turned it over and popped a couple of times which leads me to think it’s a carb problem, would increasing the main jet size help the situation or what other options are there.
P/S this seems like a duplicate post, not sure what is going on.
Thanks
 
Minimichael

Minimichael

Well-Known Member
#74
#74
Too much air is getting in. Open the mixture screw back to three or four turns. And yeah maybe drill out the jet some. Choke engaged all the way, too.
 
G

Geo46

Member
#75
#75
Mixture screw is almost out, I was thinking of making that hole into the venture a bit larger, does that control amount of fuel ? also drilling the main jet a bit larger, worth experimenting with for only a $17.00 investment.
 
sparkwizard

sparkwizard

#77
#77
That brass tube in the center of the venturi is called the emulsion tube.
It is held in by the main jet. Drilling the jet will allow more fuel. Drilling the emulsion tube is not a good idea. When you see how tiny the hole in the jet is, you'll understand. The emulsion tube mixes air with the incoming fuel so it can atomize faster in the venturi.
As @Minimichael suggested above, check for air leaks between the cylinder and the carburetor.
I am sorry for the bold text. I fat fingered it and I don't know how to turn it off.
 
Minimichael

Minimichael

Well-Known Member
#78
#78
I got my flo-jet out to see and think about why that carb was used before on your train (and we assume successfully). What about it provided the right mix-ability? Perhaps the in-line-bowl design makes the fuel that much more available or eager to join in with the air flow. And with the bowl at bottom and the path to the engine straight above it, even the fumes would be already rising up into your manifold elbow and priming the atmosphere in there, so the system is like a wick, or soaked rag, waiting for air to force it all through, together, for maximum gas:air saturation. Maybe? Not like a vacujet that first has to coax liquid out of straw before the rest of the journey.
 

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Geo46

Member
#79
#79
Interesting, but I would think the gas fumes almost at the intake through the carb would be as effective, thinking of enlarging the main jet and see what happens, it’s not working now so I can’t make it any worse.
 
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