EZGO Robin 3PG Trouble

[MoesCart]

Hello all,

First off, I would like to thank everyone here as I have been a silent observer for the last two weeks as I tinker my way through my first cart. Many of the issues I've dealt with thus far have been resolved after digging through threads I found here. I recently picked up a 1990 EZGO Marathon with a 3PG Robin which is in pretty OK shape given it's age and, of course, the price was right. That being said, I picked up the cart and a milk crate full of parts, nuts and bolts, and random garbage. Shortly after unloading I began with the removal of an absurd amount of after market wire, as always I wish I would have taken a before and after photo, I am one to tuck tape and wire loom everything. Amazingly I've been able to get everything from the crate back on the cart correctly and must say it looks pretty good... Just battling what I suspect is a fuel related issue which I will describe further after the list of things I've done so far.

- New piston, cylinder, rings, wrist pin, & related gaskets (yes I put the cylinder in the right way )
- New alternator belt
- New battery
- New battery connectors
- New spark plug
- Cleaned reeds
- Cleaned carburetor
- Removed oil injection system
- New fuel & vacuum lines
- New fuel filter
- Battled and un-seized pedal lever in potbox (considering this one of my greatest victories)
- Adjusted and cleaned rear brakes as they were far too tight
Noteworthy
- Fresh fuel
- Fuel pump recently replaced by last owner

Now for the not so fun part. I read in multiple places that many people suggested running a richer oil/fuel ratio after replacing the top end, for break in. I started with a 50:1, the cart fired right up and I ran it on jack stands a bit to ensure the clutch engaged/disengaged properly and there was no hesitation or binding in the rear end. All was well so I made the maiden voyage down the street at half throttle or so, turned around and came back up. Then made another loop down but went a bit further this time, as I turned to head back up the hill I noticed a drop in power output, nothing alarming, just sluggish and.... the amount of smoke from the back doubled. I finally made it back in to the garage to uncover and investigate. What I found was some smoke coming from the lower section of the engine, looked to be where the exhaust bolts to the bottom end of the engine (no oil leaks outside). Also, the spark plug is now a blue tint, not inside, but the portion below the porcelain. Oddly enough, when I pulled the plug, the tip looked OK, a greyish color -- not wet or blistered. I let it cool a bit and then went back out, thinking maybe this was typical break-in behavior, this time I didn't make it as far before the same result reared it's head and I feared I might toast the new top end (too lean?) so I pulled back in the garage. Unfortunately this time, the carburetor bowl decided to empty itself on the floor. I came back to the interwebs and found that just as many people suggested not running such a rich mixture so I leaned it out (128:1) and cleaned out the entire carb, everything there looked like it should and is now a bit cleaner. Went out for a test drive today and when I pressed the pedal the engine popped once or twice like it wanted to start but then just cranked with no further firing. I also noticed that now it was shooting fuel from the air jet on the top of the carburetor while cranking, so we know vacuum and fuel delivery are solid.

After all the time spent reading, tinkering, and now...yammering on and on here for you all... I am finally frustrated and have to ask the masters for some suggestions. I've read up on a new carburetor but many folks whine that they flood the engine immediately after installing, which I feel is probably user error but I don't know much about them so I've been hesitant to throw what might be more good money at bad. I need to test compression, I am confident it is good but I will check anyways. Also thinking of doing a lower seal check (for leaks) but need to get the engine firing without blasting fuel all over to be able to do that...

Again, I appreciate all the help I've uncovered so far and hope someone here has some thoughts to throw at me. Thanks!!

[StoveBolt]

Originally Posted by MoesCart

I also noticed that now it was shooting fuel from the air jet on the top of the carburetor while cranking, !!

Float bowl level set to high? needle valve stuck open?..

Originally Posted by MoesCart

I noticed a drop in power output, nothing alarming, just sluggish ....

the spark plug is now a blue tint, not inside, but the portion below the porcelain. !

Sounds like it's heating up and about to cease... ring clearance?

all I got, not a 2 cycle guy, hope someone here can help.

[CP241]

I hope when you had the engine out doing all that work you replaced the crank seals. I'm no expert on the 3pg specifically, I've only had 1 and it ate itself alive before I could do much with it lol. But... the crank seals seem to be the most common failure point on that motor. Theyll make it run lean, lose power, all sorts of problems.

A 2 stroke motor breathes through the engine case. The air comes in through the carb, through the reeds. It then Circulates inside the engine case, goes through a transfer port to the top of the piston where it is compressed, ignited, and blown out the exhaust port. So crank seals are crucial to making sure the engine case is sealed or it will leak unmetered air in through the crankshaft and cause all sorts of problems.

Also reed valve is very important. They allow the air to come in, but not back out. If the reeds are weak, chipped, or dont close all the way then air will leak back out of the intake/carb, again confusing the cycle of air in the motor.

[cart around]

Let's start easy.
The first tankful of gas should be mixed at 40:1 for break in.

Next thing.
Did you install all of the metal shrouds around the cylinder fins? They are crucial for cooling.

Moving on.
You said the float bowl dumped all of it's fuel.
From where? Did the O-ring leak around the bowl? Did you tighten up the bottom bowl nut to make it stop leaking? Did you happen to crush the bottom of the bowl a little? If so, the cross drilled hole in the center stem is blocked, and the only way for fuel to leave the float bowl is through the vent.

Getting deeper into the engine.
You put the piston in the right way. Congratulations.
Now, did you put the rings on the piston the right way? The bevel side goes up, and the ends wrap around the little pins in the ring grooves.

And finally.... Did you measure the ring end gap in the cylinder before installing the rings? They need to be measured, and filed to the right gap before installation.
If not, you will make one trip, they will get hot, expand, and tighten the piston to where it will lose power, and smoke.

[MoesCart]

Hello all,

Discovered that while cranking yesterday, not only was fuel coming out of the air jet, it was dumping back in to the air intake hose. Always a fun smell to get blasted with when hitting the garage first thing in the morning...

Unfortunately I did not do the crank seals while the engine was out, not enough forethought on my part. Luckily they are cheap and getting the engine out is a breeze. I ended up pulling the trigger on a replacement carburetor as a rebuild kit was more expensive and harder to source. After taking the OE apart again this morning I suspect the seal on the bottom of the bowl is bad. I am planning to get the new carb installed after I've cleaned and adjusted, then hopefully fire it up so I can test the crank seals.

Results of the compression test showed 127 pounds, which I imagine is sufficient. I did install the shroud around the cylinder and head so I should be good there.

Appreciate the congratulations on putting the piston in properly, figured it was worth mentioning as that is usually the first question asked when someone posts on the subject. Rings were installed correctly as well, the bevel is up and rings aligned with the pins. I will admit that I did not measure the ring end gap, I'm a bit surprised that is a thing that still needs to be done when ordering a new piston, rings, and cylinder as a kit. Do you happen to know the tolerance?


Thanks all!

[CP241]

If the fuel squirts up and away from the motor, I would say crank seals are definitely bad. There should be a LOT of vacuum coming into the carb intake to suck the fuel into the motor and not the hose...

[cart around]

If the fuel pump is working really well to put out a healthy spurt of fuel, I wouldn't be so concerned about crank seals.

Fuel spitting back out the wrong end of the carb has me worried about reed valves not sealing.

I will come back, and edit this in a minute with the ring end gap.

EDIT: You probably didn't even notice that I was gone.
The 88 manual says .008"- .016" end gap. I know yours is a 3pg, but the spec is the same.

Another EDIT: Putting the bowl on the carb is tricky. There is an O-ring in the groove that the bowl mounts to. You have to turn the carb upside down, wiggle the bowl around until you feel it positively drop into the groove all the way around, and then snug the bottom nut. That is where people get into trouble buy over torqueing the bottom nut, and crushing the bowl flat on the bottom.

[CP241]

Originally Posted by cart around

If the fuel pump is working really well to put out a healthy spurt of fuel, I wouldn't be so concerned about crank seals.

Fuel spitting back out the wrong end of the carb has me worried about reed valves not sealing.

I will come back, and edit this in a minute with the ring end gap.

True, good point.

Hope it's not reeds. They're next to impossible to find

[MoesCart]

I am also hoping I won't need to replace the reeds, can't seem to find them anywhere. One thing I noticed while cleaning is the rubbery texture on the valve body is peeling off. Luckily that coating doesn't seem to be applied or compromised where the reeds meet to make the seal so I don't think it's an issue. I will pull the valve body while I have the carb out and flip the reeds over, for good measure. I didn't notice that they were stuck open when I cleaned them but it won't hurt. I will try to get some photos of this to share.

Looking forward to getting the new carb to compare/contrast with the OE. I suspect the previous owner might have tinkered with the original and that's part of the reason why it leaked after my initial test run as I hadn't touched it prior. Will return with more details after I've installed the new.

Also, on the break-in mixture subject.... I seem to consistently find conflicting information about whether I should be running a richer oil to fuel ratio during break-in. Wiseco doesn't suggest running anything other than the manufacturer's recommended mixture, regardless of the situation but, I've seen many here and elsewhere that state otherwise. Is this merely a preference thing, maybe I hang in the 85:1 range for the first tank as a "happy medium."

Thanks for the help and confirming the ring end gap!

[Dabble Inn]

It states it in the 2pg repair manual to run 40:1 for the first tank, then 128:1 after that. I would bet the 3pg does too