Motor won't rev up on 88 marathon rebuild

nsmithjr · 10-19-2014, 05:25 PM

Just did a complete overhaul on my 88 marathon. Starts up great give it some gas and the motor won't rev up much. If I back off the footfeet and press down again it goes a little faster. I understand things need to be seated and broken in, but I think it should have more pickup. Any suggestions are greatly appreciated.

93yellowclubcar · 10-19-2014, 05:34 PM

First thought that immediately springs to mind is the piston. It's a fresh rebuild, but make sure the square hole on the piston is facing the intake. Check this FIRST, even if you think you got it right, cause it'll make you chase false problems and curse if it happens to be backwards. Been there, done that. Best way to check is take the header pipe off the head and spin the engine by hand, you should only see the blank side of the piston, no square port.

Second thought is a plugged muffler, IF after checking the piston, it is correct, put the head pipe back on but leave the muffler unhooked. It will be loud. If the running improves, muffler is plugged and needs BBQ'd.

nsmithjr · 10-19-2014, 06:34 PM

I checked myself a couple times on the piston. But I could have put in backwards, i will check that out. Muffler has been bbq'd. Thanks for the advice., I'll keep you posted.

sccowboy · 10-19-2014, 08:57 PM

After the piston verification, how about the fuel pump and if flowing well then the carb.

redcloud · 10-19-2014, 09:34 PM

Check your throttle linkage and make sure you have a carb that is opening up. If that is ok I would do a filter replacement and clean carb. If still a problem check that the fuel pump is connected right and that you are getting a good pulsing when you crank the engine.

nsmithjr · 10-19-2014, 10:06 PM

Thanks, going to check the piston to make sure. Has 2 new fuel filters installed. I'll check the fuel pump also.

nsmithjr · 10-23-2014, 05:35 PM

Changed fuel pump, and its getting fuel. Piston is installed correctly. Did change the plug, helped some, I might have gotten carried away with the lubrication when installed the rebuilt kit. Cylinder walls show quite a bit of oi in it. Don't know if this is all my issue. Any suggestions what tomcheck next will be greatly appreciated. Thanks

BrewCityMusic · 10-23-2014, 06:31 PM

Did You totally disassemble and thoroughly clean the carb, including cleaning the jets and setting the float? A small piece of poo-poo in the jet will stall You out like You are describing ... You didn't mention the cables, are You sure the choke is opening and closing FULLY - also if You open the throttle by hand does that help IE is it travelling all the way to full open? Just a few immediate thoughts

nsmithjr · 10-24-2014, 05:02 PM

I never er disassemble the carb. I did install new fuel filters. I may have taken the carb for granted fore it was working betore I took the engine apart. That will be my next thing to doniscthe carb. Can you tell me how to make sure the float is in the correct position. Thank you.

BrewCityMusic · 10-24-2014, 05:57 PM

Start here - the circled jets are the ones You want to focus on, blow them out good with compressed carb cleaner (the spray can stuff) and make sure they have all the holes, etc open 100% ... The float should sit level with the needle valve closed - with the float bowl off and the needle and float in place, push the float up *just* until you feel the needle valve seat - you should be level or just a hair under it.

10-19-2014, 05:25 PM	#1
nsmithjr Getting Wild Join Date: Jun 2009 Posts: 84	Motor won't rev up on 88 marathon rebuild Just did a complete overhaul on my 88 marathon. Starts up great give it some gas and the motor won't rev up much. If I back off the footfeet and press down again it goes a little faster. I understand things need to be seated and broken in, but I think it should have more pickup. Any suggestions are greatly appreciated.
nsmithjr Getting Wild Join Date: Jun 2009 Posts: 84

10-19-2014, 05:34 PM	#2
93yellowclubcar ΜΟΛΩΝ ΛΑΒΕ Join Date: Nov 2012 Location: West Virginia Posts: 4,094	Re: Motor won't rev up on 88 marathon rebuild First thought that immediately springs to mind is the piston. It's a fresh rebuild, but make sure the square hole on the piston is facing the intake. Check this FIRST, even if you think you got it right, cause it'll make you chase false problems and curse if it happens to be backwards. Been there, done that. Best way to check is take the header pipe off the head and spin the engine by hand, you should only see the blank side of the piston, no square port. Second thought is a plugged muffler, IF after checking the piston, it is correct, put the head pipe back on but leave the muffler unhooked. It will be loud. If the running improves, muffler is plugged and needs BBQ'd.

10-19-2014, 06:34 PM	#3
nsmithjr Getting Wild Join Date: Jun 2009 Posts: 84	Re: Motor won't rev up on 88 marathon rebuild I checked myself a couple times on the piston. But I could have put in backwards, i will check that out. Muffler has been bbq'd. Thanks for the advice., I'll keep you posted.
nsmithjr Getting Wild Join Date: Jun 2009 Posts: 84

10-19-2014, 08:57 PM	#4
sccowboy It ain't gonna be easy. Join Date: Apr 2008 Location: St. George, SC Posts: 1,480	Re: Motor won't rev up on 88 marathon rebuild After the piston verification, how about the fuel pump and if flowing well then the carb.

10-19-2014, 09:34 PM	#5
redcloud Gone Wild Join Date: May 2013 Posts: 320	Re: Motor won't rev up on 88 marathon rebuild Check your throttle linkage and make sure you have a carb that is opening up. If that is ok I would do a filter replacement and clean carb. If still a problem check that the fuel pump is connected right and that you are getting a good pulsing when you crank the engine.
redcloud Gone Wild Join Date: May 2013 Posts: 320

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10-19-2014, 10:06 PM	#6
nsmithjr Getting Wild Join Date: Jun 2009 Posts: 84	Re: Motor won't rev up on 88 marathon rebuild Thanks, going to check the piston to make sure. Has 2 new fuel filters installed. I'll check the fuel pump also.
nsmithjr Getting Wild Join Date: Jun 2009 Posts: 84

10-23-2014, 05:35 PM	#7
nsmithjr Getting Wild Join Date: Jun 2009 Posts: 84	Re: Motor won't rev up on 88 marathon rebuild Changed fuel pump, and its getting fuel. Piston is installed correctly. Did change the plug, helped some, I might have gotten carried away with the lubrication when installed the rebuilt kit. Cylinder walls show quite a bit of oi in it. Don't know if this is all my issue. Any suggestions what tomcheck next will be greatly appreciated. Thanks
nsmithjr Getting Wild Join Date: Jun 2009 Posts: 84

10-23-2014, 06:31 PM	#8
BrewCityMusic Hammer Down !!!! Join Date: Jun 2010 Location: Lake Geneva, WI Posts: 2,681	Re: Motor won't rev up on 88 marathon rebuild Did You totally disassemble and thoroughly clean the carb, including cleaning the jets and setting the float? A small piece of poo-poo in the jet will stall You out like You are describing ... You didn't mention the cables, are You sure the choke is opening and closing FULLY - also if You open the throttle by hand does that help IE is it travelling all the way to full open? Just a few immediate thoughts

10-24-2014, 05:02 PM	#9
nsmithjr Getting Wild Join Date: Jun 2009 Posts: 84	Re: Motor won't rev up on 88 marathon rebuild I never er disassemble the carb. I did install new fuel filters. I may have taken the carb for granted fore it was working betore I took the engine apart. That will be my next thing to doniscthe carb. Can you tell me how to make sure the float is in the correct position. Thank you.
nsmithjr Getting Wild Join Date: Jun 2009 Posts: 84

10-24-2014, 05:57 PM	#10
BrewCityMusic Hammer Down !!!! Join Date: Jun 2010 Location: Lake Geneva, WI Posts: 2,681	Re: Motor won't rev up on 88 marathon rebuild Start here - the circled jets are the ones You want to focus on, blow them out good with compressed carb cleaner (the spray can stuff) and make sure they have all the holes, etc open 100% ... The float should sit level with the needle valve closed - with the float bowl off and the needle and float in place, push the float up just until you feel the needle valve seat - you should be level or just a hair under it.

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