a disclaimer, decarbonising the stock muffler is lots of work but if your bike is lacking power you only have 2 options, buy new or fix
a short background story, i have been chasing a lack of power on my kdx200 H series in australia, even after a full engine rebuild done by me and many days,weeks,months trying to get the jetting right it just never had much power, always felt like the main jet was too rich even though i was running small main jets and at one point right down to a 138 main jet,same thing, no power,lots of smoke. what puzzled me more is when i bought the bike it ran terrible but even so it had a screaming top end power delivery , what happened to the power? it then occurred to me that several years earlier i sold the aftermarket muffler that was on it and replaced it with a stock muffler, hoping to quieten it down which it didn't. so through powers of deduction it has to be the stock muffler at fault and so i decided to cut it open and find out whats going on,lets get the angle grinder
i cut it open just guessing where to cut as like i say there appears to be zero information on the internet, you can see the carbon mess in the photos and i had no idea what a spark arrestor looked like until i saw it in real
ok now that its opened up its time to soak it in a hot caustic soda bath, i bought a cheap chinese heater as caustic soda only works when hot, i left it for 24 hours and covered the tall bucket with an old blanket to lock in the heat, i pulled it out several times to pressure clean, i had to make a multi hook cleaning scraper from a piece of tig wire to scrape out the carbon from the baffle tubes and midpipe, everything was baked on solid, the spark arrestor needs extra attention and i used a boroscope up the back side to check for any residual carbon of which there was lots
now before you say why go to all that trouble,just put a blow torch up the end and burn it out, there is a few reasons why this can't be done, firstly burning out carbon is a myth, its the oil you see burning not carbon, carbon burns at 3000 degrees Celsius and steal melts at 1100 degrees Celsius ,secondly the main body of the muffler is filled with perforated sheets and fibreglass, a blow torch would burn the fibreglass and render its sound dampening qualities useless, thirdly the spark arrestor is brazed in not welded so you might melt the brazing, lastly the main body is a baffle/chamber design , any carbon would be trapped in there
so after removing all the carbon i washed it,let it dry in the sun for a day then tig welded it back together, mig welding won't really work, i already tried
how does it perform? baby we are back in action, power restored, i had to start jetting from fresh and went back to a 165 main jet with E10 gasoline, the sound dampening qualities of the muffler are also back,it has a beautiful 2 stroke sound as it did from new instead of the horrible ear piercing sound so common with many bikes, the engine combustion sound also seems quieter, you young guys won't appreciate a quiet bike now but trust me you will do when you are older
i have 3 kdx's between 2 different countries and i won't begin to try and perfect the jetting until the other 2 mufflers are cut open
how kawasaki thought this was a good design is beyond me especially when the kdx250sr had the same baffle design but is fully rebuildable
hope this helps some people out there that are searching for the missing power and youve already tried everybodys special oil ratio and brand reccomendations
