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PW50 Expansion Chamber / Baffle Full Of Fibers

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Hey Guys,

Got a 2008 PW50 and owned it for a year.

Went through the maintenance items I can handle myself and one of them is to clean / inspect the spark arrestor.

I found ours was full of fibers. I cleaned them all out from the arrestor and the tailpipe but then discovered the expansion chamber / baffle is stuffed full of them.

Seems really strange to me. Is the stock expansion chamber baffled with fiberglass or similar and does it eventually start breaking down and clogging up the works? 

It looks a real mess in there and am considering replacing the expansion chamber and exhaust manifold piece to get the little thing breathing better.

Any thoughts or opinions?



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Sounds like either a really small rodent tried to make a home inside or perhaps a PO thought it was the type of silencer that uses packing (it's not to my knowledge, but I'm not a PW50 guru either.) Clean it out as best you can and run it till your son or daughter is too big for it. The PW50s are not worth the effort to modify and most used buyers are looking for an unmolested (except maybe for freshened graphics and grips) starter bikes for a toddler.

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After some more research found out that they come that way and eventually the baffling does start breaking down.


Cleaned out tailpipe, spark arrester and expansion chamber as best I could then ran it without the tailpipe on. Blew out a few clumps of stuff then settled down. Put the tailpipe back on. 


I'll just keep an eye on it and make sure the tailpipe doesn't plug up.


The official Yamaha replacement seems to run about $140 and the offshore knockoffs for about $70 on ebay. I just wish I could take the expansion chamber apart and clean it out but it's totally non serviceable.

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