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I've been hunting around the net for an after market expansion chamber for my 91 250. It's bored out to 258cc and has some porting done. I'll do the jetting last.

The only option I have found is the fmf fatty pipe.

Is there others? Any links or points of direction would be greatly appreciated.

Cheers

There is nothing wrong with the fatty....any other brand pipe will cost around the same, just go with what's know to be a good pipe.

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For any KDX, think of every company that ever made pipes, then see if there is one for your KDX on their website.

Thanks, for the info. I'm showing my ignorance, but I don't know who the exhaust manufactures are. I'm really only finding fmf and pro circuit, who make a muffler but no expansion pipe. I'm happy to go with the fmf fatty if people can report from experience. Or any other, if the exist.

Pretty much every company has dropped the KDX250 pipe since it was last made in '94. I'm shocked to hear that FMF actually still makes one. Having said that, any other pipe you'll have to keep your eye on ebay to find a used or NOS one. I know I have the Pro Circuit one and it worked really well on my 250.

Cheers SS109, petty much what I'm finding, 2/5 of stuff all. Google wasn't finding anything for me, even image searching led me back to eBay and fmf.

Looks like I'll go get myself a FATTY.

Try this guy, Rich I think is his name, price is around the same as FMF, and he can adjust the pipe to suit your needs, http://www.dynoport.com/ and http://www.dynoport.com/250_KDX_1991-1994._1994-95, they are in New York so shipping to Australia might be a killer.

Thanks Asewell, kind of thing I was asking for. I have emailed and see what happens. Cheers.

I went with the fmf fatty. $216us delivered to Australia. The dynoport option was $340us delivered. With exchange rate it put me up to $460. I'm not racing it so doubt I'd get the benefit for the extra money. Coupled it up with a pro circuit closed track silencer, so you should be able to hear me coming.

Wow. That is a fair difference in price. Congrats on getting the exhaust. Don't be afraid to keep it quiet, though.

Yeah it adds up on my end. Week Aussie dollar. It's on the snail mail so could be 6 weeks until I see it. Suspension is next @ around $450 front and back. It will be a $2k bike by the time I'm finished. Just picked up an 84 TS250x for $300, so I can bet that will drain the bank too. Bloody bikes are fun.

91kdx250 wrote:I went with the fmf fatty. $216us delivered to Australia. The dynoport option was $340us delivered. With exchange rate it put me up to $460. I'm not racing it so doubt I'd get the benefit for the extra money. Coupled it up with a pro circuit closed track silencer, so you should be able to hear me coming.

Nice choice. Please post a short video with sound once you're done installing it. I'm curious about the sound.

Will do, it will be later in the year though. You know how these resto's drag out.

My FMF Fatty turned up but it's for a KX. It's spring mounted not with a flange and bolts. Anyone has successfully fitting these together? Waiting on a response from the supplier as to what their offer to resolve is.

We in the USA don't have the flange and bolts, just springs.

What is the model number?

Others have cut the flange off the stock pipe and welded it to aftermarket.