Slightly Underpowered

Cisco

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I took the baffle out of a Kawi 90 and thought, man this thing sounds like it has more power. It didn't really, so I put the baffle back in. My neighbors were grateful. ;-)
 

inspectorcritic

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I've always been curious about that. The stock mufflers aren't tuned expansion chambers, but they do allow for a little back pressure. Does the engine really run better with an open exhaust, or is it just louder?
Yes, it runs more bitter and louder it only takes 3 minutes to take a 10mm nut off tap the muffler remove the guts. It does much bitter at hill climbing take it out try it, then please let me know your test results I don't want to give people false hope.
 

DAMIEN1307

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Yes, it runs more bitter and louder it only takes 3 minutes to take a 10mm nut off tap the muffler remove the guts. It does much bitter at hill climbing take it out try it, then please let me know your test results I don't want to give people false hope.
You need to have some back pressure on 2 stroke motors...If not, you shorten the life of the motor.
 

inspectorcritic

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You need to have some back pressure on 2 stroke motors...If not, you shorten the life of the motor.
What about drilling about a half-inch hole in the middle where goes into the bend I would still have some back pressure and expedited exhaust.
 

Cisco

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The stock exhaust is interesting. The inlet tube is perforated, then the exhaust gas has to go upward through a baffle plate to the outlet tube (which is almost as long as the muffler section). I was thinking of cutting the outlet tube shorter. I wonder if that would work better.
 

Cisco

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I have been contemplating this for a while. The outlet tube extends through the baffle plate. I assume (never assume) that the baffle provides some acoustic dampening. The baffle sits about halfway in the muffler section, above the perforations and below the top of the outlet tube. I was thinking of cutting the outlet tube so that it extends only about half an inch through the baffle. Not much of a modification, only a few inches shorter. I was also thinking of taking the baffle out and cutting the outlet tube much shorter. There is enough space between the inlet tube and the wall of the muffler to slip in a sleeve of thin fiberglass (glass pack). The fiberglass could be held in place by a very light weight, expanded sheet metal sleeve. I was also thinking of drilling out the perforations that I could reach (just a few of the lower holes). So, that would give a little bit better flow through and some sound dampening. The external part of the outlet tube would remain the same. I have to believe that some thought went into the engineering of the stock exhaust. It's been used for decades.
 
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