New member: I recently purchased a stock 2007 KLX300(still had the little rubbery spindly things on the knobbies). I've done all the Free Mods. Rejetted the carb per the advice found on here. K$N filter. I also "helped" the stock exhaust breath better with the help of a 5/8 drill bit into the cone inside(riding in high desert; not the forest). The spark plug looks great after riding.

After researching this site and several others, I purchased an FMF Powerbomb header #042155 and a Powercore 4 can #042000. Header fit perfect! Unfortunately, the muffler pipe swallows the header where they meet; they do not fit. Is this normal? Is there some kind of joint adapter missing from my purchases? Both pieces are marked with the appropriate model numbers and as I understood it, these are the appropriate model #'s for the bike. So what did I do wrong? These clearly do not fit together, nor does the muffler into the stock header. It's literally the same diameter so I can't use it as a slip on.

Ideas???

 

I don't know my part numbers but my fmf slip-on fit both my stock header and the fmf header without as much as a clamp to hold it and I have no leaks.

 

That is great info, sadly, it doesn't make my two piece fit together any better I hope my dilemma doesn't become a $400 education I get no benefit from.

 

Are both the header and the muffler for KLX 300, not for 250?

The stock 300 header - muffler joint is larger diameter than 250 joint (header pipe is same diameter), so you might have got a "300" slip-on muffler and a "250" header.

--
Mikko

 

Hmmmm...here's what I know for sure

Stock 300 muffler-fits stock header(no brainer, I know), but is same diameter of FMF header.

FMF Powercore 4 muffler-packaging and directions are listed as muffler for KLX250/300. Does not fit the stock header(same diameter), and swallows the FMF header. Matter of fact, you can bury the header all the way into the muffler pipe until the first curve.

FMF Powerbomb-bolts right up in place. Fits beautifully on the bike.

Me-

 

I just fitted a fmf Q4 & a fmf megabomb to my bike. The header was specific to the klx250 but the silencer said klx250/300......The silencer fitted perfectly into the header but I used the original clamp with some hi-temp sealant.



The problem I had was the closeness of the silencer to the airbox with melting issues until I jiggled things about.

 

Ok, let me ask this: Is the Powercore muffler designed to be the male end, fitting into the header pipe, just like the stock muffler does?

Or, is the header supposed to be the male end. The header does have a expansion around the tip as if it is to receive the muffler just the way the stock is designed.

I know this may all sound a bit elementary, but I'd really like to have any hidden facts which might have escaped me before I make contact with the merchant I purchased it from. All the mods which I previously mentioned were done by me so I would like to think I can figure out a simple muffler configuration.

Thanks for all the help.

 

Head pipe = 38MM. fwiw

 

After reading all this sounds like a miss match,but ease to over come...here's what I would do...take your Slip-on and header to a Muffler shop and get your header end pipe opened up on the end to fit right in your Slip-on....done

 

this would be the easiest route...takes the muffler shop seconds to do this...