87 Marathon 2 cycle performance issue

panelbeatr · 06-01-2011, 11:41 AM

I did a full rebuild on my engine and had great performance,then after a few months it started bogging down and only seems to to about half speed so I replaced the drive belt,that was badly worn, and the drive (crank mounted) pulley, that was making noise, the spark plug, and still have poor performance. Before I replaced the drive pulley & drive belt it seemed to run better in reverse?? I also drained the fuel and replaced it with fresh mixed fuel. I'd removed the oil injection system when I rebuilt the engine. It did seem to run better with the choke pulled about half way out which makes me wonder if the crank seals (new) are leaking. One of the seals popped out so we peened over the metal around the replacement seal to secure it. The factory manual mentions a plugged muffler, somthing my kart guy says he's only seen once...??? BTW I did put some sunoco race gas (maybe a quart or so) we had left over from my SCCA club racing fuel testing before it started acting up.

madoc1 · 06-01-2011, 12:14 PM

what ratio are you running. it should be 128/1 after initial tank. you can loosen up the muffler and try it, it might need a bbq.

amesmotorsports · 06-01-2011, 12:22 PM

I got a 89 EZGO and had the same issue you have, It would run good and then seem to just petter out. Last year I put a brand new carb on it. It worked good. Then it started doing the same thing I just didn't understand it. I put a new drive belt on it, New plug, Wire, Fuel filter and new gas line. I just could not figer it out. So I went out and got another new carb and that's when I seen what was wrong. I put the new carb on. The old new carb was missing the mixture screw so it was sucking all air. It runs great now no problems at all.

panelbeatr · 06-01-2011, 02:14 PM

Thanks for the update .... I'll look tonite - BTW do you have any X-tra 89-92 2 cycle parts - see my other post

panelbeatr · 06-12-2011, 10:00 AM

OK- I've done all the following to solve my plight - new spark plug - old one looked nice & tan - Burned out muffler twice on cured out hedge wood fire - replaced noisey drive clutch & belt - that helped some - replaced driven clutch that was absolutely shot - that helped more on top speed. I removed & thourghly cleaned the carb and checked over fuel system for blockage and tested fuel pump output. My drive clutch was pretty noisey - could the vibration on the crank cause the crank seal to fail - the motor only has about half a season on it. I starts very hard and requires a ton of choke to start and keep running. I put a clothes pin on the choke to keep it pulled out some. Once running it goes about 75% top speed but is a real dog out of the hole. I used to only pull the choke out 1/2" for just a few seconds of running and then it would go like hell (as much as a marathon ever could) I used to run 50:1 mix and it ran pretty good - now I've made it about 100:1 with little improvement - HELP ANY ONE???

panelbeatr · 06-13-2011, 10:35 PM

Good -Bad news. My cart kept running worse and worse - wouldn't start or restart except with full choke. Had to keep choke pulled out at least half way to keep runnning. Motor rebuilt - 135# compression. Put up on lift looking at rear seal leak and found gasket between block and cyl blown out - shoved gasket back up into place and torqued cyl bolts back down and ran great!! Had about triple the low end torque and top speed as well...almost scared me ...

racin161 · 06-14-2011, 06:44 AM

Just my thought but your probably living on borrowed time without replacing the gasket but it's good news you've found the problem.I would consider replacing it SOON.

panelbeatr · 06-14-2011, 04:04 PM

That's the plan.... I've spent so much time & effort on this thing I may have the cart repair shop do it for me. All the repair stuff I've done has resulted in a really great running cart. I may have forgot to set the studs tight in the block before I torqued the jug nuts down, so the treads may have loosened up in the aluminum block. I was really happy to see the 135 pounds of compression. The one clue I got was how poorly the fuel pump was working because of the reduced crank case pressure.

racin161 · 06-15-2011, 07:20 AM

Base gasket & head gasket $15.00 a cart that don't run $0000000

06-01-2011, 11:41 AM	#1
panelbeatr Getting Wild Join Date: Sep 2010 Location: NE KS Posts: 111	87 Marathon 2 cycle performance issue I did a full rebuild on my engine and had great performance,then after a few months it started bogging down and only seems to to about half speed so I replaced the drive belt,that was badly worn, and the drive (crank mounted) pulley, that was making noise, the spark plug, and still have poor performance. Before I replaced the drive pulley & drive belt it seemed to run better in reverse?? I also drained the fuel and replaced it with fresh mixed fuel. I'd removed the oil injection system when I rebuilt the engine. It did seem to run better with the choke pulled about half way out which makes me wonder if the crank seals (new) are leaking. One of the seals popped out so we peened over the metal around the replacement seal to secure it. The factory manual mentions a plugged muffler, somthing my kart guy says he's only seen once...??? BTW I did put some sunoco race gas (maybe a quart or so) we had left over from my SCCA club racing fuel testing before it started acting up.

06-01-2011, 12:14 PM	#2
madoc1 no clue Join Date: Sep 2009 Location: spicewood, texas Posts: 3,308	Re: 87 Marathon 2 cycle performance issue what ratio are you running. it should be 128/1 after initial tank. you can loosen up the muffler and try it, it might need a bbq.

06-01-2011, 12:22 PM	#3
amesmotorsports Gone Wild Join Date: May 2011 Location: Michigan Posts: 271	Re: 87 Marathon 2 cycle performance issue I got a 89 EZGO and had the same issue you have, It would run good and then seem to just petter out. Last year I put a brand new carb on it. It worked good. Then it started doing the same thing I just didn't understand it. I put a new drive belt on it, New plug, Wire, Fuel filter and new gas line. I just could not figer it out. So I went out and got another new carb and that's when I seen what was wrong. I put the new carb on. The old new carb was missing the mixture screw so it was sucking all air. It runs great now no problems at all.

06-01-2011, 02:14 PM	#4
panelbeatr Getting Wild Join Date: Sep 2010 Location: NE KS Posts: 111	Re: 87 Marathon 2 cycle performance issue Thanks for the update .... I'll look tonite - BTW do you have any X-tra 89-92 2 cycle parts - see my other post

06-12-2011, 10:00 AM	#5
panelbeatr Getting Wild Join Date: Sep 2010 Location: NE KS Posts: 111	Re: 87 Marathon 2 cycle performance issue OK- I've done all the following to solve my plight - new spark plug - old one looked nice & tan - Burned out muffler twice on cured out hedge wood fire - replaced noisey drive clutch & belt - that helped some - replaced driven clutch that was absolutely shot - that helped more on top speed. I removed & thourghly cleaned the carb and checked over fuel system for blockage and tested fuel pump output. My drive clutch was pretty noisey - could the vibration on the crank cause the crank seal to fail - the motor only has about half a season on it. I starts very hard and requires a ton of choke to start and keep running. I put a clothes pin on the choke to keep it pulled out some. Once running it goes about 75% top speed but is a real dog out of the hole. I used to only pull the choke out 1/2" for just a few seconds of running and then it would go like hell (as much as a marathon ever could) I used to run 50:1 mix and it ran pretty good - now I've made it about 100:1 with little improvement - HELP ANY ONE???

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06-13-2011, 10:35 PM	#6
panelbeatr Getting Wild Join Date: Sep 2010 Location: NE KS Posts: 111	Re: 87 Marathon 2 cycle performance issue Good -Bad news. My cart kept running worse and worse - wouldn't start or restart except with full choke. Had to keep choke pulled out at least half way to keep runnning. Motor rebuilt - 135# compression. Put up on lift looking at rear seal leak and found gasket between block and cyl blown out - shoved gasket back up into place and torqued cyl bolts back down and ran great!! Had about triple the low end torque and top speed as well...almost scared me ...

06-14-2011, 06:44 AM	#7
racin161 Gone Wild Join Date: Feb 2011 Posts: 1,515	Re: 87 Marathon 2 cycle performance issue Just my thought but your probably living on borrowed time without replacing the gasket but it's good news you've found the problem.I would consider replacing it SOON.
racin161 Gone Wild Join Date: Feb 2011 Posts: 1,515

06-14-2011, 04:04 PM	#8
panelbeatr Getting Wild Join Date: Sep 2010 Location: NE KS Posts: 111	Re: 87 Marathon 2 cycle performance issue That's the plan.... I've spent so much time & effort on this thing I may have the cart repair shop do it for me. All the repair stuff I've done has resulted in a really great running cart. I may have forgot to set the studs tight in the block before I torqued the jug nuts down, so the treads may have loosened up in the aluminum block. I was really happy to see the 135 pounds of compression. The one clue I got was how poorly the fuel pump was working because of the reduced crank case pressure.

06-15-2011, 07:20 AM	#9
racin161 Gone Wild Join Date: Feb 2011 Posts: 1,515	Re: 87 Marathon 2 cycle performance issue Base gasket & head gasket $15.00 a cart that don't run $0000000
racin161 Gone Wild Join Date: Feb 2011 Posts: 1,515

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