KDXRIDER.NET

ok guys, decarbonising of the stock kdx200/220 muffler, this might be the number 3 most important thing you can do/check if your bike is lacking power or more specifically top end power, jetting being number 1 , kips valve function being number 2, yet there is zero information on this as far as i can tell

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

after cleaning

Coat of engine enamel and it's barely noticeable

WOW! Great job to get it sorted out like that. The end result looks terrific. Great explanation as well. Thank you for taking the time to write it up.

Daryl, this is awesome to see & hear about. The carb jetting aspects of your summary are really interesting. The photos are, too. Thank you for sharing.

QUESTION: What was the concentration or water dilution ratio of the caustic when used it?

Cheers guys, I don't know the caustic ratio, I just put some in and hoped for the best but I will guess 100 grams to 25 litres

Was there a brand name to it? I might not can get it here, but maybe I can study it and find something locally that is similar. I have a whole lot of pipes I need to one day clean out.

Also, do you think it would work on the ceramic of a spark plug? I have several that are blackened, but not fouled.

Thank you.

KDX-G, I'm surprised you say it's difficult to find. This is a centuries' available industrial chemical. You want the cheapest you can find. To help with your request, here's images from Home Depot and Amazon showing packaged products.

Failed to mention, the chemical compound for caustic soda / lye is sodium hydroxide. Searching for this compound may locate the least expensive material price.

KDXGarage wrote: 12:18 am Jul 29 2025 Was there a brand name to it? I might not can get it here, but maybe I can study it and find something locally that is similar. I have a whole lot of pipes I need to one day clean out.

Also, do you think it would work on the ceramic of a spark plug? I have several that are blackened, but not fouled.

Thank you.

The issue with spark plugs is the threads are cadmium plated, I think the caustic soda would eat this away in no time, same goes for most metals non ferrous

I was at a garage sale last month and the old guy was selling a sand blasting unit specifically for spark plugs, apparently popular back in the old days, he wanted 5 dollars for it and now kicking myself I didn't buy it

Do you think the inside area of the plug would be plated? They are short Iridium plugs I paid about $12.50 each years ago. NGK BR8ECMIX

I would have tried the plug machine on some cheap ones just for fun.

billie, I tried to buy some Red Devil lye about 20 years ago. Clerk said it was pulled from shelves due to drug making. EDIT: maybe locally or at that store, maybe not nationally

KDXGarage wrote: 03:17 am Jul 30 2025 billie, I tried to buy some Red Devil lye about 20 years ago. Clerk said it was pulled from shelves due to drug making. EDIT: maybe locally or at that store, maybe not nationally

KDX-G, Weird because that sounds like something that happens in CA. I bet grocery stores have it and, if not, you can get sodium hydroxide from Amazon and Home Depot (delivery).

Daryl, did the spark plug blaster look like this? I have one of these. Bought it as a teenager from the automotive catalogue mail order business J.C. Whitney.

The blaster in this stock photo is advertised for $33. I prolly paid $3.50 for mine, including grit. It's a little bit messy, but works.

Yes it was something similar to that, the idea seemed to make sense,
Kdxgarage, as said caustic soda is the chemical sodium hydroxide, also known as drain cleaner, it's available everywhere, even in the supermarkets

Thank you both for all the info. The 2005 KX125 and KX250 plugs ain't cheap. :-)

Harbor Freight has or used to have a similar spark plug cleaner. I have one, but have never used it. I would not want to try it on iridum plugs.

Yeah, I wouldn't sand blast iridium plugs, either

Billie, I see the Instant Power brand is at a local Walmart. Thanks for the info!

Wow.... Great read, KDXDazz. I'm surprised to learn the OEM '94+ 220 / *'95+ 200 uses a sealed (welded/brazed) design like this...(prone to clogging!).

I've been envious of the stock '91-'94 KDX250 US-model and KDX200E spark arrestors, and if I hadn't found a couple of old NLA Acerbis 035 KDX200H/220R spark arrestors (longer baffles than the current aftermarket offerings), I'd be running a modified/adapted KDX250 unit on my 220 models I'd imagine the KDX250SR is similar to the North American off-road model '91-'94 KDX250?




I've got that exact same spark plug sandblaster, although I have yet to hook it up and use it. I have, however, used two older but similar units that my father has, quite a lot, and report that they work very well.

Also, I'd like to comment that I, too, appreciate a quiet running bike... The modern KTM mufflers on their off-road line ('04-ish & newer, after they stopped using spark arrestors) are so nice and quiet, always leaving me jealous! It's because they are substantially long, and don't have a spark arrestor taking up 7" of space at the end of the muffler, and instead have 7" more perforated baffle tube in addition to the already longer perforated baffle tube. They purr quite nicely, but are not legal in National Forests and State Forest OHV trails, sadly.
I would trade in my spark arrestor for a quieter exhaust if it were legal, as I don't believe a spark arrestor is truly needed on a 2-stroke.

Aging up there at 47 and coming from a background of loud music, sheet metal tin knocking work,loud fast street bikes, and lots of mechanical work and remodeling/maintenance work hammering on things with no ear protection, my tinnitus is quite bad, my ears ring 24/7 and I've had to train myself to ignore it. They've become hyper sensitive to loud noise to the point where it hurts to be around loud sounds without hearing protection, and I can't even ride a motorcycle at 70mph on the highway for any longer durations even WITH a quieter helmet for long distances without the best of earplugs due to the extreme decibel level of wind noise...
I very much appreciate a quiet bike.