1983 Marathon Engine Trouble

devadasy

1983 EZGO Marathon golf cart

Robin Engine
Model: EC25-2PG
Disp: 244cc
Motor: 83-08185

(1) 45 lbs compression
(2) piston is not tight in cylinder has room to move side to side
(3) good spark
(4) top of piston and head is black and caked on
(5) oil pump removed
(6) starter/gen needs a new belt (still works)

when it runing this year it smoked all the time and did not have speed it had in the past. fuel mixture and specs on engine to check for wear I do not have. I am trying to figure out why it has low compression.

Service Manual is also needed for Engine

BGW

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rusty shackel

with that much carbon on top of the piston the ring might be locked in the groove,
that would cause the low # on compression .


rusty s

Dave Box

I think that if the piston moves from side to side then the reason you have low compression is that it is just worn out. You can get a new cylinder and piston kit for around $200. If that engine is even running at 45 psi it is a miracle of modern engineering.

Dave

BrewCityMusic

I'm with Dave on this one - lateral movement is a really BAD thing ... as is 45psi (which also astounds me that it even fires, might want to double check that number but either way, time for a top end)

Figure as long as you have the engine out to do the top end, you may as well pick up a set of crank seals for $14, you'd REALLY hate to fire up a nice tight new motor and blow one or the other down the shaft and have to pull the motor again.

And, your ratio should be 128:1 (1oz 2-cycle oil per gallon of gas) - if you're running higher that could have something to do with the smoking, etc (although again, 45psi about says it all). You can run a bit higher ratio for the first couple of gallons with the fresh rebuild (40:1 is spec for "break in") , but after that just go to 128:1

Check the "Tech" section at the top of the forum for your manual

devadasy

in the tech section at the top I could not find a manual covering a 1983 2pg

also I checked an older running ezgo with same compression tester and the tester gave a reading of around 105 lbs easy I did retest the engine with 45 lbs a few times the highest reading was not even 50 lbs. the piston moves enough in the cylinder that you can see it when moving it by hand. for the last few years you needed to choke it alot to start it or even get speed out of it. the only tools i have for measuring piston and cylinder are a caliper. the cylinder felt smooth with the piston down and the piston lookeda little beat up on top with a bunch of tiny dents on it looks like someone removed the piston before and left those marks from a tool.

Dave Box

The bottom line is that with the piston loose in the cylinder and less than 90 psi it is shot so don't even bother measuring it. As regards a manual you will be hard pushed to find one for an 83 -1983 was the oddball year for the 2pg engine. The muffler was placed behind the engine and it layed down instead of standing up. The '83 golf cart had a different engine frame, muffler & exhaust stack. It only lasted one year though...lots of problems. However the manual is pretty generic so as long as you get one for 81 - 88 that will be fine.

Of course if you go down the route of replacing the top end (and as BCM says, you must also replace the Crankcase oil seals) then there are plenty of guys here who will help you. In that vein here is some advice. Grab hold of the clutch that is attached to the engine, now try to move it up and down. If it moves you have crankshaft bearing issues and this is going to have a huge effect on your future decisions.

Dave

ScooterMcTavish

And with the smoking issue this year, I would suggest that the fuel mixture isn't getting fired properly, throwing tons of gas and oil into the muffler. While you have the muffler out with the engine, this would be a good time to BBQ the muffler.

devadasy

where would I find a engine for the machine if I wanted to replace it instead of rebuilding and how much would it cost. I have one spare engine now but it has an internal starter and the shroud is missing I was using it for parts it came off a extra part machine. I forgot to get the model numbers off it. I cannot do a compression test untill i figure out how to fire the starter up on it to see if it was even possible to use that engine instead

ScooterMcTavish

Really a rebuild isn't that tough of a job, reasonably inexpensive, and you'll have a "like new" engine when you're done, complete with new crank seals.

If you wanted to replace the engine (if you can find one or a donor cart), it likely hasn't been rebuilt, and you will probably inherit problems similar to the ones you're having with your current engine.

Just my $0.02, but I'm personally happy to know that my cart should be running good for years due to my rebuild.

devadasy

I dont know if I will need a new cylinder or not I am not sure what size pistons you can get up to. Like if the cylinder is still usable I will maybe have it redone and buy an oversized piston kit that comes with rings pin and piston. if not I will buy a new topend kit that comes with cylinder and piston and the rest of parts. as for the head I have no clue what to do it does not look like they are included with kits or seperate and the one on it needs cleaning bad without damaging it. I will be buying new gaskets and seals just to be safe.