Hello, I have picked up a 2018 kx250 exhaust for a good price and am just lining things up now to get it fitted to a KLX250efi.
So far it looks like what I will need to do is cut the mid pipe at the right spot and weld in a reducer so it will fit to the header “I bought a used klx300r header that has the wider bell at the end but don’t have it in hand yet”
My question is can someone with callipers measure the inside diameter of the 300r header at the bell on the end.

Thanks !

 

Mine should be the same as yours.
On my stock 300 header, the flared end that the compression band goes around has an inside diameter of 36mm and the inside diameter of the stock 300 exhaust gasket is 34mm. When I ordered an aftermarket midpipe, they sent me a 34mm 250 part which slipfit fine inside the stock 300 gasket.

 

Thanks ! That should be just what I need.
I think I will put together a small build along post later once I get it going.
It maybe an option for people who arn't interested in dropping hundreds on a slip on that probably isn’t even in stock these days.

cheers!

 

Please do, Captain.

I built my own exhaust and am always interested in seeing new ideas.

 

[QUOTE=tooter;554712]Please do, Captain.

Just a quick update with some info I found. Looks like the newer EFI 250 and EFI 300 share the same header.
Tooter I believe the ID measurement you gave me would be appropriate for these two bikes.
The headset that I’m intending to start with is one from a 2007 300r. This should be wider in that bell section and about an inch longer.
Any idea the ID of this header at that end coupling?
rhe reason I chose this combination is so that if this project doesn’t work out I can move on and use other headers designed for the 300r, like a FSW pipe.

Thanks

 

[QUOTE=Capt.150;554786]Yes, they do. The headers for both the 250's and 300's have been the same for at least 7 years. There is more variation in the midpipes. The Dual Sport and SuperMoto midpipes are S shaped with a horizontal muffler,


...while the R midpipe is L shaped with a upward slanted muffler.



I prefer the aftermarket DS and SM style midpipes over the R midpipes because they're longer for more low rpm torque.

I also really like the FMF Megabomb header because it's no only larger in diameter than the stock header, it also has an added expansion chamber which creates added torque producing exhaust volume. It performs just like a longer head pipe, but in a shorter space.