1985 EZ-GO Marathon

[Shaggy]

The buggy forums seem to suggest the lower diaphragm is broken, thus causing gas to enter the crank case (flooding)

I guess? But I bought a new one ?

Strange but I've gone through it to, where i buy a new carb and its crap right out of the box. Great build thread btw. What forum you on for the ezgo?

 

[Vbb199]

Strange but I've gone through it to, where i buy a new carb and its crap right out of the box. Great build thread btw. What forum you on for the ezgo?

I actually am not on any forum. This is just something I've wanted to own for a while, and my chance finally came up so I took it.

 

[Vbb199]

^

I had already disassembled the pump and inspected the diaphragm, but being as it's clear plastic maybe I overlooked a tear?

I guess I'll look again later today

 

[Vbb199]

I looked into this again recently, I pulled the fuel pump off to inspect the lower diaphragm for fuel leaking into the crank case.

No go?
But I found excess flashing covering the hole for the pump

As the crank rotates, on the downstroke it pulls a vacuum and pulls the diaphragm down, pulling gas into the pump, and on the upstroke, it compresses the diaphragm and squirts it into the carb bowl.

I thought maybe this blocked hole was the source of my struggles, as it turns out, it's not. I poked it out, reinstalled, tried to go for a drive, still flooding.

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at this point I'm literally out of ideas. Dunno where to go from here. I guess I could buy all new seals and gaskets instead of reusing the old ones, but I can't really see how that'd help now, unless it's not generating enough crank case pressure to suck the gas into the combustion chamber ?

That'd be about the only other thing I know to do at this point

It's ran, and I drove it all over the place limiting the fuel via bending the float, or the vise grip method, so I don't have any reason to think my piston is in backwards, and it ran in reverse too. So I dunno.

If anyone has some input that'd be great.


This seems possibly Reed related too? I bent the reeds and tweaked them until they were flat with the plate and barely any light shined past them with the lights off. Maybe I need to give it a second look and see what's going on with them.

 

[Blue Ox]

Is it possible you've got the wrong pump and it's supplying too much pressure for the float to control? What you're describing really sounds like a flooding/mixture problem, not an inherent engine problem. I'd put a gauge on it and see how much fuel pressure there is. It really shouldn't need much. Is there a spring in the pump? There must be something to regulate it.

 

[Vbb199]

Is it possible you've got the wrong pump and it's supplying too much pressure for the float to control? What you're describing really sounds like a flooding/mixture problem, not an inherent engine problem. I'd put a gauge on it and see how much fuel pressure there is. It really shouldn't need much. Is there a spring in the pump? There must be something to regulate it.

That is what I thought.

But it's basically a top plate, a center plate (which contains two little plastic discs to seal off the flow , one on the bottom for input, one on top for output), and the bottom plate which I sent a pic of that seals against the crank case.

Sandwiched in between those 3 plates is rubber gaskets, and plastic diagrams.


I hope you appreciate my cool little drawing hahaha

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[Vbb199]

Here's a shot of the bottom of it.

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[Vbb199]

It's supposed to be like, 2-3 psi to the carb to operate correctly.

Other than that, I don't see how it regulates pressure?!?!

I theorized Maybe me being "too precision" with my piston fitment is too much crank case pressure.? Lol idk what else. But thanks for your input @Blue Ox anything additionally is appreciated. Im basically in the echo chamber hoping someone will bounce some good ideas back.

 

[WFO]

I think I would go through that Mikuni and through it back on. Those commie carbs just don't cut it.

 

[Vbb199]

I think I would go through that Mikuni and through it back on. Those commie carbs just don't cut it.

I've heard that several times from multiple people, maybe I will.

At this point, since I poked out the flashing on the pump, now it won't even run at all.

Just hoards of gas at the intake

 

[Vbb199]

I just purchased an adjustable 1-5 psi inline regulator.

Arrives wednesday.....

I'll post updates when it arrives... maybe that's all it needs

 

[Blue Ox]

They used to use pumps similar to that on small outboards. It's been a long time since I fiddled with one, but my recollection is that they used crankcase pressure (or vacuum) to drive the diaphragm one way, and a light spring to do the actual pumping stroke.

Much like a mechanical fuel pump on our trucks, the spring is what controls fuel pressure. When the spring force can't overcome fuel pressure the pump stops pumping until the pressure subsides and the spring can push fuel again.

Your one picture with the O-ring in the center looks like there might be a check ball in the center. That would make sense for creating a one-way crankcase driven stroke.

 

[Vbb199]

They used to use pumps similar to that on small outboards. It's been a long time since I fiddled with one, but my recollection is that they used crankcase pressure (or vacuum) to drive the diaphragm one way, and a light spring to do the actual pumping stroke.

Much like a mechanical fuel pump on our trucks, the spring is what controls fuel pressure. When the spring force can't overcome fuel pressure the pump stops pumping until the pressure subsides and the spring can push fuel again.

Your one picture with the O-ring in the center looks like there might be a check ball in the center. That would make sense for creating a one-way crankcase driven stroke.

Now you got me wondering if something fell out (or wasn't included)

 

[Vbb199]

Well yesterday I finally solved the mystery.

I said to myself, if this don't run by tonight, I'm selling it. Tired of messing with it.


My regulator arrived. But first I checked current fuel pressure.
3 psi.

For giggles, I put the regulator on ANYWAYS, and set it to 3 psi.

Flooded.

Turned it down to .5 psi, flooded.

TF?!??!?!?!?!??!?!?!?!?

Lol. We'll get there.

I started thinking and thinking and thinking. And did some MORE thinking.

It's aspirating the gas.
Just not like it should.

When you roll it over, the carb horn is dry, but when the motor stops, raw gas comes out the carb.

It's unable to successfully pull it thru to the combustion chamber, unless you drastically limit the fuel input.

It CAN run on crank case gasses (like when it leaks them past the reed), which means it's pulling them thru to the piston on compression alone.

The 2 cycles are being completed as long as gas is in the crank case solely.

So it's..... not passing thru the Reed like it should. That's what I thought.


So I pulled the carb off again, and intake, and low and behold I found an issue. Wasn't the solution, but an issue nonetheless.

I spy with my little eye, an air leak!

notice the debris that attempted to enter the crank case via a leak at the intake.

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So I cleaned those gaskets for now, stoned the piss out of all surfaces to get them nice and clean, assembled, torqued to spec, and tried again.

Flooded!

Dammit!

So I thought OK, it's really going up for sale. F it



Then I decided, momma didn't raise no b!tch, so I'll keep messing with it lol


I got out the vacuum/low fuel psi gauge, removed the screw in the intake , and checked vacuum at the reeds. Low rpms it was like a very bouncy 10.

High rpms it was like 2 in/hg, steadily.

I didnt realize at the time like a dummy, the "boom boom" is what makes the vacuum.

i was confused, thinking like a regular 4 stroke motor, that it needed more vacuum to open the reeds.

lol
so i started playing with throttle positioning....

As in, throttle blades position in relation to when the starter motor began rotating.


I drained all the gas out of the motor, set it so the motor would begin running with the throttle cracked a little, and viola!
It ran. Ran a little lean at the low rpms (like deceleration would cause a popping), so I opened the low speed idle screw a little.

Deleted the regulator.

Tried again. It was a little smoky, but I felt better it was smoking lightly than no smoke. No risk of overheating.

And maybe my mix ratio was a little heavy.
Somewhere around 40:1 or 3oz to 1 gallon is appropriate mixture.

It died in the lawn after after riding around for a bit.

I put more gas in, and it sure enough took right back off!

Now that I FINALLY have a reference point of where it should be, I can fine tune it where I like and have it happy.


As I stated in my first post, this is my first in depth experience of a 2 stroke, I just assumed it needed to be closed off since a "pressurized system" was ideal.

Yes and no.

I needed the air snorkel on while the throttle was cracked, and it would create enough pressure to run stably.

Thats wonderful though.

I'm gonna swap tires and lift with a friend this weekend, and then it can be all tricked out.


Another notable thing I just tried that I'm unsure if it did anything or not is, I pulled the cap off of the oil injection port on the top of the bowl?

That doesn't make sense why it would need to be uncapped, but I'll put it back on mid driving and see if it floods out again .

I understand there has to be air for the venturi affect to work, but I assumed the low speed idle screw and the throttle is all the air it needed ?

We'll see.

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[Vbb199]

I also want to add there's a screw to set "idle" with. The old mikuni didn't have one, but this one did ? I utilized it anyways, to set "closed" on the throttle plate.

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Seems good, you can stomp it and it'll take off, or decel, then resume speed.

I probably need to lean it out a little. It sounds like it's a little fat based on engine load at low rpms. But we'll get there!


I'm no dummy with carbs.

But I like my holley carbs @Paladin

Since this isn't a holley, I'll have to learn a little. But I got an OK course in small engine carb tuning over the course of this little problem solving.


I'll get the WOT afr where I like it and my low speed afr happy, and it should be great!

I need to get my old beer bottle cap choke cable out, and install it as well, so I can stop reaching down in there to open the choke by hand haha