1990 marathon muffler vibrations

dan161 · 06-14-2013, 07:41 PM

I have a 1990 marathon with the pg3 motor. I am having alot of problems with vibrations with the muffler and it constantly keeps breaking my exhaust pipe coming from motor to muffler. The muffler is clamped tightly on the flat pan which is bolted with 4 bolts to the subframe that the engine is bolted to.

I can grab the muffler and it doesn't move and seems very tight and secure. But at certain rpms is creates a very fast vibration where the muffler almost looks like its blurry because it virbrating so fast. The pipe going to the ground from the muffler also vibrates really fast.

It almost seems like something is missing that helps to hold things secure from the vibrations. Need any ideas that you can provide me as its ruining the pipe. Thanks in advance!

1989Marathon · 06-14-2013, 07:49 PM

I had the same problem until I swapped out the bolts between the pipe and the muffler. I installed longer bolts, with springs, and nylock nuts. I just tightened them up enough so it wouldn't leak.

dan161 · 06-14-2013, 08:03 PM

thats a good idea to give it a little wiggle room. Do you have anything under the muffler or does it just sit on the flat piece of aluminum and get clamped to it?

1989Marathon · 06-14-2013, 08:04 PM

Nothing under the muffler. Just the header wrap.

dan161 · 06-14-2013, 08:32 PM

Thanks for the help. I've been doing some research and am wondering if possibly my motor is cracked at its base where it mounts in the engine cradle. I just have this sneaky suspicion that something else is not right also based off all the other issues I have found with this cart.

1989Marathon · 06-14-2013, 08:34 PM

Probably not the motor, but the motor cradle. Mine was cracked right where it turns up in the front.

dan161 · 06-14-2013, 08:44 PM

Ok thanks. If I can get this fixed then I can try and figure out why it just doesn't seem to have the power I think it should. Get a couple adults and kid on it and it barely seems like it wants to go up hills.

1989Marathon · 06-14-2013, 08:47 PM

Power spring in secondary clutch = climb hills.

rvkersh · 06-15-2013, 04:52 AM

Between the head pipe and starter belt, there is a brace bolted to the motor, it is also bolted to the muffler pan underneath. Look under to see if that bolt has fallen out, that will cause the problem you have. I have seen this several times. If the engine has been out before, it is easy to forget to tighten that bolt when putting it back together because you can't see it from the top.

dan161 · 06-16-2013, 09:54 PM

I have the power spring in the secondary clutch. I should say I guess that it will climb the hills but I could literally get out and walk faster. And it has around 110psi on compression so thats pretty good. New carb and fuel pump also.

I will have to check the bolt mentioned. The motor was taken out by previous owner but I don't think he did anymore then finger tighten all bolts. Might just be it. Thanks

06-14-2013, 07:41 PM	#1
dan161 Getting Wild Join Date: Apr 2013 Posts: 106	1990 marathon muffler vibrations I have a 1990 marathon with the pg3 motor. I am having alot of problems with vibrations with the muffler and it constantly keeps breaking my exhaust pipe coming from motor to muffler. The muffler is clamped tightly on the flat pan which is bolted with 4 bolts to the subframe that the engine is bolted to. I can grab the muffler and it doesn't move and seems very tight and secure. But at certain rpms is creates a very fast vibration where the muffler almost looks like its blurry because it virbrating so fast. The pipe going to the ground from the muffler also vibrates really fast. It almost seems like something is missing that helps to hold things secure from the vibrations. Need any ideas that you can provide me as its ruining the pipe. Thanks in advance!
dan161 Getting Wild Join Date: Apr 2013 Posts: 106

06-14-2013, 07:49 PM	#2
1989Marathon Gone Wild Join Date: Oct 2010 Posts: 6,730	Re: 1990 marathon muffler vibrations I had the same problem until I swapped out the bolts between the pipe and the muffler. I installed longer bolts, with springs, and nylock nuts. I just tightened them up enough so it wouldn't leak.
1989Marathon Gone Wild Join Date: Oct 2010 Posts: 6,730

06-14-2013, 08:03 PM	#3
dan161 Getting Wild Join Date: Apr 2013 Posts: 106	Re: 1990 marathon muffler vibrations thats a good idea to give it a little wiggle room. Do you have anything under the muffler or does it just sit on the flat piece of aluminum and get clamped to it?
dan161 Getting Wild Join Date: Apr 2013 Posts: 106

06-14-2013, 08:04 PM	#4
1989Marathon Gone Wild Join Date: Oct 2010 Posts: 6,730	Re: 1990 marathon muffler vibrations Nothing under the muffler. Just the header wrap.
1989Marathon Gone Wild Join Date: Oct 2010 Posts: 6,730

06-14-2013, 08:32 PM	#5
dan161 Getting Wild Join Date: Apr 2013 Posts: 106	Re: 1990 marathon muffler vibrations Thanks for the help. I've been doing some research and am wondering if possibly my motor is cracked at its base where it mounts in the engine cradle. I just have this sneaky suspicion that something else is not right also based off all the other issues I have found with this cart.
dan161 Getting Wild Join Date: Apr 2013 Posts: 106

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06-14-2013, 08:34 PM	#6
1989Marathon Gone Wild Join Date: Oct 2010 Posts: 6,730	Re: 1990 marathon muffler vibrations Probably not the motor, but the motor cradle. Mine was cracked right where it turns up in the front.
1989Marathon Gone Wild Join Date: Oct 2010 Posts: 6,730

06-14-2013, 08:44 PM	#7
dan161 Getting Wild Join Date: Apr 2013 Posts: 106	Re: 1990 marathon muffler vibrations Ok thanks. If I can get this fixed then I can try and figure out why it just doesn't seem to have the power I think it should. Get a couple adults and kid on it and it barely seems like it wants to go up hills.
dan161 Getting Wild Join Date: Apr 2013 Posts: 106

06-14-2013, 08:47 PM	#8
1989Marathon Gone Wild Join Date: Oct 2010 Posts: 6,730	Re: 1990 marathon muffler vibrations Power spring in secondary clutch = climb hills.
1989Marathon Gone Wild Join Date: Oct 2010 Posts: 6,730

06-15-2013, 04:52 AM	#9
rvkersh Gone Wild Join Date: Apr 2012 Location: Dansville, NY Posts: 396	Re: 1990 marathon muffler vibrations Between the head pipe and starter belt, there is a brace bolted to the motor, it is also bolted to the muffler pan underneath. Look under to see if that bolt has fallen out, that will cause the problem you have. I have seen this several times. If the engine has been out before, it is easy to forget to tighten that bolt when putting it back together because you can't see it from the top.

06-16-2013, 09:54 PM	#10
dan161 Getting Wild Join Date: Apr 2013 Posts: 106	Re: 1990 marathon muffler vibrations I have the power spring in the secondary clutch. I should say I guess that it will climb the hills but I could literally get out and walk faster. And it has around 110psi on compression so thats pretty good. New carb and fuel pump also. I will have to check the bolt mentioned. The motor was taken out by previous owner but I don't think he did anymore then finger tighten all bolts. Might just be it. Thanks
dan161 Getting Wild Join Date: Apr 2013 Posts: 106

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