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Muffler Baffle Removal


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#1 artbuc OFFLINE  

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Posted August 21, 2010 - 11:05 AM

While I am waiting for my new mower, I decided to tackle a problem that has been bugging me for years. Something is loose in my muffler and the rattling drives me nuts. I cut open the muffler and discovered both baffles (I assume they are actually spark arrestors) were loose. All of the tack welds had failed. I removed both baffles and patched her up.

Question, other than spark arresting, what else do these baffles do? Anything critical? I assume they do put a little back pressure of the engine so I am concerned about now running too lean. Also, I wonder if these baffles help isolate the cylinders from each other?

I have a Kohler Magnum 18S engine. Each cylinder exhaust pipe connects to a opposite end of the twin muffler which is about 5" in diameter and a foot long. At each end there is an entry chamber and then the spark arrestor which is (was) a 5" disc with radial slots. After the exhaust gas leaves its respective spark arrestor it enters a perforated pipe which exits the center of the muffler.

Thanks for your help. A new muffler costs $258. Yikes!

Edited by artbuc, August 21, 2010 - 11:32 AM.


#2 olcowhand ONLINE  

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Posted August 21, 2010 - 12:12 PM

You'll be good to go. The main thing is to have a chamber of any type, and then the baffle tube exit helps quiet things down. Running a short straight pipe or no pipe at all is harmful to the valves & alters the mixture a lot, but you should have nothing to worry about. If after running a while, the spark plugs show it is running lean, then you could always narrow the outlet on the muffler to slightly increase the back pressure, but I doubt you'll need to.

#3 artbuc OFFLINE  

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Posted August 21, 2010 - 03:29 PM

You'll be good to go. The main thing is to have a chamber of any type, and then the baffle tube exit helps quiet things down. Running a short straight pipe or no pipe at all is harmful to the valves & alters the mixture a lot, but you should have nothing to worry about. If after running a while, the spark plugs show it is running lean, then you could always narrow the outlet on the muffler to slightly increase the back pressure, but I doubt you'll need to.


Thanks. What about one exhaust interfering with the other? I took a good look at the baffles/spark arrestors. They have 8 radial slots which redirect the exhaust gas. I would think these baffles "kill" the exhaust pulse and help it leave the muffler chamber instead of traveling past the perforated exit pipe and heading towards the opposite cylinder.

BTW, what is the purpose of these baffles? Are they spark arrestors?

#4 olcowhand ONLINE  

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Posted August 21, 2010 - 03:37 PM

The exhausts won't affect the opposite cylinder. When running, the entire inside is pressurized pretty much equally no matter what parts are in there. The plate does make more turbulence, which will help it to be quieter, plus helps kill sparks. That's my 2 cents anyway.

#5 artbuc OFFLINE  

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Posted August 21, 2010 - 04:30 PM

The exhausts won't affect the opposite cylinder. When running, the entire inside is pressurized pretty much equally no matter what parts are in there. The plate does make more turbulence, which will help it to be quieter, plus helps kill sparks. That's my 2 cents anyway.


I believe you. For kicks and giggles I'm going to talk with Nelson (now Fleetguard-Nelson owned by Cummins) on Monday to see what they say.

One of the baffles was blown in half, I'm guessing by a backfire years ago. The other baffle was in place although all of the tacks had failed. The cylinder with the blown baffle was running richer than the other so I don't think the baffles were adding enough back pressure to lean out the engine.

I do really appreciate your help. Will be back again soon, I'm sure.

#6 olcowhand ONLINE  

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Posted August 21, 2010 - 05:24 PM

With a more open exhaust, they actually run leaner. Motorcycles for instance require jetting up to larger sizes when adding a free flowing performance exhaust.

#7 artbuc OFFLINE  

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Posted August 21, 2010 - 07:06 PM

With a more open exhaust, they actually run leaner. Motorcycles for instance require jetting up to larger sizes when adding a free flowing performance exhaust.


Right. That is why these baffles don't appear to add significant back pressure. The baffle that was actually blown away was on the cylinder that was running richer. The only other explanation is that cylinder was actually running super rich and the blown baffle was helping to lean it out.

#8 olcowhand ONLINE  

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Posted August 21, 2010 - 07:10 PM

Right. That is why these baffles don't appear to add significant back pressure. The baffle that was actually blown away was on the cylinder that was running richer. The only other explanation is that cylinder was actually running super rich and the blown baffle was helping to lean it out.


Gotcha! I was interpreting wrong.

#9 DH1 ONLINE  

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Posted August 21, 2010 - 07:29 PM

Just a thought here but the cylinder that was running rich was it the lower or higher one?
Some times gas pools in the manifold and finds it's way to the lower cylinder making it run richer than the upper one.

#10 artbuc OFFLINE  

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Posted August 21, 2010 - 09:06 PM

Just a thought here but the cylinder that was running rich was it the lower or higher one?
Some times gas pools in the manifold and finds it's way to the lower cylinder making it run richer than the upper one.


Sorry, but I'm not following. I think both cylinders are the same height. What do you mean by lower/higher?

#11 DH1 ONLINE  

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Posted August 21, 2010 - 09:19 PM

To be honest not familiar with the engine you have, I know some opposed twins (vert. shaft) 1 cly. sits higher than the other, just thought if there was a low spot in the intake manifold any liquid gas would find it's way down to the lower cylinder.

#12 artbuc OFFLINE  

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Posted August 21, 2010 - 10:12 PM

To be honest not familiar with the engine you have, I know some opposed twins (vert. shaft) 1 cly. sits higher than the other, just thought if there was a low spot in the intake manifold any liquid gas would find it's way down to the lower cylinder.


Thanks. I have the Kohler Magnum horizontal shaft. The intake manifolds is supposed to be level but you make a good point. Maybe there is a restriction or some other irregularity that is causing a maldistribution of gas. I'll check it out.




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