1985 EZ-GO Marathon

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so i figured i should post this up, because its been a little bit of a project ive been working on in the background.

last year i picked up a 1985ish ez go marathon, around christmas i think. my buddy found two of them for like, 600$ bucks, which is a steal, and said, "hey if i go load these and buy them, will you pay me back like, 400"

i said sure, why not, we live on a ton of property (mine or family owned), it would be cool to have a buggy to ride around, or even (because ii work down the drive) ride to and from work and never even start the car.
(i have to start the car during school days because my dad takes my oldest to the same school my brother attends, and i dont want to make her walk all that way, and quite frankly, i sometimes dont like the walk lol)

anywho, i also figured it would just be a nice buggy for drunk shenanigans, or taking trash to the dumpster, etc. maybe if its reliable, even do something cool like drive it in the bed of the c10, drive the c10 on the trailer, then go to a drag race event, have the buggy to ride around the event.... you get it.

 

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i never got to doing much with it because my son was born Jan 7th, but before little man was coming, i was working on it. it came with the motor, exhaust, all starter motor wires loose.
no belts.
carb unbolted.

this was my first 2 stroke project on a more in depth level.

its a 244cc robins 2 stroke. 2.835 bore by something stroke.


before jan 7th i was determined to get it running. so i started off by putting everything together.

i played some games with belt lengths for the starter motor, and had a cvt on order; but had finally gotten it where it would roll over with jumper cables attached to the battery leads (didnt have a battery)

upon attempting to crank it, we discovered it wasnt even getting fuel, the bowl didnt fill. right off i checked the fuel pump (sends fuel to the carb based off of crank case pressure pulses) it had a broken diaphragm. so i ordered a new one.

 

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despite a new pump, alot of haggling with sketchy wires, and everything else, it just wouldnt run! lol so i figured.. maybe it just has no compression. and sure enough, the exhaust was huffing for air, and the intake was blowing fuel out! no suction!

previously (because i didnt have a compression gauge on hand, i rolled it over before installing it in the buggy by hand, with no spark plug, and it blew my finger off the hole, so i fiugred it had "ok" compression.

i tried to rig up a oil pressure gauge to the cylinder head, rolled it, i only saw 5 pounds, i figured it was an error because of liquid vs air ? yeah.... ill get to it.

after learning it was running in reverse, i went and got an actual compression gauge, rolled it over, only saw 5 pounds.... HA the irony!

so i took it back out, dissembled it , and what i notably saw upon cylinder disassembly was, some bolts someone started loosening, then left alone (mainly on the jug)

the piston had been grenaded. the cylinder walls badly damaged! the rings were stuck in place because the aluminum had rolled over them, even the wrist pin bore had been rolled lol.


someone didnt add oil to their mix, assuming the old oil injection system still existed.... WRONG!

yea it was ******.....sheesh!

it got hot in there lol

 

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i notably want to add somewhere in here, during my backwards operating motor, i checked the reeds, bent them, tweaked them, etc until they were flat and light wouldnt pass by them.

so i called the local cart shop, told them my situation, and said i needed to bore my jug, what piston sizes are available. the man says they offer stock, "25 over" and "50 over" pistons. note the emphasis.

so i figured, hell, lets shoot for 50 over, and ill do it myself on the mill with a boring head, make it slick as glass, and nothing else! so i did.

stock bore being 2.835", i made it 2.885" ..yayyyyyy it was done! and looked ******* awesome!

the 50 over piston was on back order or something dumb, but my buddy had a "25 over" and "50 over" piston on his shelf. he says... uh yeah.... might wanna look at these"

sends over a pic, and sure as **** they say .25mm and 50mm cast on them.

thats about .008" and .019" lol

so no doubt, i overshot the bore, badly. it was dead.

 

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so i ordered another jug on fleabay, for 50$ it was used and abused. but machinable. stock bore

 

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got it bored to the appropriate size, which was 2.854, i had the piston in hand, the mfg specs was .004-.006" piston clearance, i think i hit about .003 and left it.


brought it home, got the new rings in the bore, i file fit them, since i got a tight bore clearance tolerance, i went on the high end of the ring gap tolerance, which was .016"

assembled, put it all back in with the starter motor, hooked it up, etc.


the next day was gonna be the "the day" (this is now about a 1 week ago)

 

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it ended up sitting a bit, and i didnt have good 2 stroke oil for the break in and ring seating. so it went on like that in idle mode until 2 days ago.

i had issues with it pouring gas out, gas, gas ,gas and more gas. and that **** isnt cheap these days! it kept flooding like a mfk!

so after some deductive reasoning, a couple smoke sessions, some brews, and some research, and fiddling, i started investigating deeper.

i learned i had good crank case pressure, because i could remove the fuel pump, and it was spraying the crank case gasses out.

i had good compression (without using a gauge) because it would run really fast without a spark plug, and the minute i blocked the hole off with my hand, it would bog it down, and not to mention the intake was trying to suck my hand in like a diesel motor! lol

so i tried (and yes, go aheda and cringe) unhooking the gas lines, and running it for a brief 2 seconds on carb cleaner, and it fired right off and ran!

so i knew what i had would function, it was a matter of MORE carb fiddling, mainly the metering area, as we know it, the bowl and float.


took it apart yesterday, only to find debris in the needle and seat. PO hadnt appeared to ever change the fuel filter, it was one of the first things i did earlier before the attempted first fire off.

cleared the whole carb out, rolled the motor over with no spark plug, and emptied everything of the excess gas.

it was ready.


tried again, only to have it completely flood again. lol


so i said f it, im going inside for the night.


thought on it over night, i knew it had to be float level. i knew the needle and seat were cleared.

 

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so today i came out with a fresh new outlook, ready to make **** happen. my buddy came out, we fiddled, we took it apart, and started bending the carb float around. each tweak, we would reassemble, and try it.

first couple times, it would run! then die.

we kept messing, finally got it where it consistently ran!!!! great!

so i hooked the cvt belt up, jacked the rear diff up, and tested if it would turn the tires (to try to simulate load) it was a no go, because there was no tire resistance, it wouldnt spin very fast. no biggie.

we replace the old jerry rigged "battery tray and fuse box" piece of wood with some fresh wood, rig up some bs with electrical tape to prevent the car battery from contacting the exhaust, and ratchet strapped it down. for testing purposes. lol

i made a seat (buggy didnt come with one) out of a piece of 3/4 ply wood (thats like, pouring gold down the drain these days)



we hopped on, went to head off, and it just ran briefly at high rpms, stalled, then died. did it several times. ok.

intake was drooling gas, so i knew it was still flooding it.


took the carb off, started tweaking the float some more, but this time, using calipers to measure how much i bent the tab. at this point, i KNEW something was wrong, because you dont have to do this to make a carb properly meter fuel lol. you set the float once, and dont again. maybe minor tweaks, but nothing more!

anyways, the tab being bent up .130" seemed to be the magic number... for a little bit.

it fired up, it ran, it drove, i drove it all over, holding 1 throttle position the best i could at lower rpms to try to seat the rings, occasionally going up in higher rpms, etc.


i drove it down to my dads, it died in his yard.

made an awful squeaky noise, but the motor just flat stopped, no more boom.

i thought... its dead... the bore was too tight, it locked down on it and the rings dug in...

so i let it rest for like, 1 min, got back on, it took right back off and ran! but it was slobbering gas like a bitch, but it ran FAST uphill. had a strong reverse too.

so i continued playing with float tab heights, to no avail. i would try a gap of .135, it was too lean, then at .125, it was too fat. and any other format from .120-.160" but there was no happy medium... either it was flooded or it was no fuel in the bowl.

so i just said... this is stupid, setting a float shouldnt require all this lol


i set the float like a normal float, at full lift (shut off) the float is parallel to the base, assembled, tried again, it flooded it so bad i couldnt get it to run again. f it.

i pulled the jet to try to inspect it, the numbers arent legible, so i have no idea what it is, i cannot find any information on the web about jetting for these mikuni carbs, it seems to be tribal knowledge. i did deduce the orifice is about .035", but i dunno how that helps me since i have no reference, and it seems likely, the PO ma have fiddled, even drilled the jet out.

so i ordered a new carb. its 20$ on amazon, wong **** replacement.

so its chilling in limbo, until the carb arrives.... so ill post another update when it shows up, im just a bit clueless as of now...

the low speed idle screw i set at closed, then 1.5 turns back out. theres no air leaks, great crank case pressure, diaphragm on fuel pump isnt cracked, the exhaust still blows, the intake still tries to tank my hand with it, i have a healthly blue arc on the plug, i have confirmed timing (coil input voltage) does increase as engine speed increases.


if anyone has some info for

1. tuning the metering rod (theres alot of thread adjustment )
2. appropriate jet sizing (orifice hole, sea level, blah)

it would be appreciated.

i did come across some articles, someone said, they run a 80 or an 85 jet, and it works for them fine thru their travels, from 1000 feet to 6000 feet.

i live at 780ish feet elevation.

i cant say if the jet is right or wrong, because as i said, i have no reference to go from lol

theres different metering rods, but i also cannot find information on them, so im just ordering a new carb, hoping its "generic configuration" is close enough for it to just run with no issues, then fine tune it from there.

 

[Vbb199]

I've purchased a cheapo , arrives the 28th....

 

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Got on the buggy yesterday after letting it sit for a week, just to see what would happen, stepped on the gas and it immediately took off!

Then a little into it, flooded out and died again.

Lots of smoke from the tail pipe..

So I feel like it's a runner,, just lacking a solid carb..

New carb arrives today, I figure I'll give it a little attention this evening while working on the suburban.

I did notice regarding the "mystery" of the mikuni carbs and their jets, my friends presumably operational 88' had a 95 jet in it.... interesting....

It's looking like maybe mine was drilled out, I was considering asking if I could borrow it to try and fire mine up, but I figured I'd wait until the Chinese repro comes, and then go from there.

 

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Once I get it running I'll rip the stupid monster stickers off, get a proper front seat, and maybe get some cool speakers going.


It did come with fully functional headlights and taillights, as well as functional turn signals.

Maybe rattle can it another color or something, I dunno.


My friend has a lift kit and bigger tires he offered to trade me for my stock lift and tires, I figured in order for it to belong in a "b-rate hillbilly " fleet, it needs to be lifted on bigger tires so I can fk around and flip it later while I'm drinking beer

 

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Parts have arrived. So it's time to play soon.

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Heh..... so I had a learning experience tonight,
Installed the new carb, flooded out.... I thought damn. OK wtf

Pulled the fuel line to empty the excess gas from the crank, it ran!
Ran for a little on crank case gasses, then stalled out.


So then it hit me...
TOO MUCH FUEL INPUT! lol

I still dunno why the now NEW needle and seat isn't metering the fuel like it should, but I took a vise grip to the fuel line, kept playing with tension.

But I got it running, I drove it all over place, but I believe i had it too lean, it locked up on me 1 time lmao

Let it cool, tried again. But this time more on the richer side, so it was smoking like a mf

on straight distances, at higher rpms, it would do really good, but up hills I had to pinch it tighter, didn't lock up tho , I rode it all over with the kids for quite a while, constantly playing with "fuel pressure"

Keeping it rich so it wouldn't overheat again.

So I guess I need a regulator?

I thought this was the purpose of the "fuel pump" it regulated psi, but I guess not, presumably because I have such excellent crank case pressure, it's pumping a shitload in?

I dunno

I wish I had a little more info/help on these motors

Perhaps I'll think on it some more until I get a regulator

 

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I failed to attach a photo

 

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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 ?