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Inexpensive exhaust "silencer"...

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I recently acquired a new 2020 Coleman Outfitter 400 and overall am quite pleased with it. I had the "too be expected" loose bolts (first thing I checked), all related to the final assembly conducted by the pimple-faced kid "mechanic" at Tractor Supply.--the bolts in the upper driver's side roll bar joint were just hand tight, as were those of the upper seat belt anchors--but other than that it had been pretty well assembled.

The included owner's manual  is not current; it speaks of using the choke to cold-start the motor (it's EFI, no choke),  and shows the ignition and lighting switches as dash-mounted when in fact they are on the steering column. It also direct you to remove the seat to change the spark plug--except that on this revision the cylinder tilts rearward and the cylinder head in found beneath the dump bed. Other maintenance tasks are similarly ill-described and it is generally useless.

I did find the exhaust note to be a bit strident and devised the following to tone it down a bit. I used one of those inexpensive 1" NPT female inlet B&S "muffin" mufflers that have been around for decades, and a steel 1" EMT to steel box adapters that have been available for a like time:




1" EMT has an outside diameter of 29.5 mm, the tailpipe extension on the beast is 28 mm O.D.--so I use a partially overlapped  cylindrical shim spacer of 28 ga. (0.47 mm) galvanized sheet metal to fit the EMT adapter to the tailpipe . Bedded well in muffler putty the single set screw on the adapter mounted it up quite firmly.On my first ride I found the motor to feel and sound a bit constipated--so i drilled out the 106 1/8" holes in the faced of the muffin to 9/64". This is a 26.5% increase in area [(9/64)^2 / (1/8)^2 = 1.2656]


That made the difference needed to restore proper flow without making it too loud again:It



is arguably not a pretty as some of the $100+ aftermarket alternative, but at $15 for the muffler and adapter it better fits my budget.Make sure you get the genuine B&S part (# 392989) as the 3rd party clones lack an inner baffle that makes them inherently louder than the B&S piece.



FWIW--I  also  removed the front anti-roll bar--and have found little to no adverse effect on handling (and arguably some positive effect)--it also got rid of an annoying  rattle from the low-quality driver's side roll bar tie-rod end. Put in an iridium spark plug too...



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