Installing a FMF Q4 On My Kawasaki KLX250S – Vlog/How To


I was very lucky in that my recently purchased KLX250S came with an FMF Q4 slip on. Now I’m not sure if you know much about KLX250’s, but they aren’t exactly power houses. Every little bit helps though right? Time to put that bad boy on!

First off, I’m pretty sure that the bike has already been jetted for the exhaust. Why? The previous owner said he put the stock exhaust back on because it was too loud for the riding he was doing. The air box has also been modified. The top of the air box has been completely replaced with a piece of aluminium with some holes drilled in it. I was going to mod the air box myself, so that’s one less thing I have to do.

The pipe was bloody dirty, so I cleaned up the pipe with some soapy water and a dish washing pad. It came up great.

For those who have never installed an aftermarket pipe yourself, don’t ever pay a shop to do it. It’s usually just a couple of bolts. In my case it was a simple case of taking the side cover off, popping the seat off and 3 bolts. I was unfortunate in that my header pipe flange was a little out of shape in one part. That’s second hand bikes for you, easy fix though. In order to get it back into shape, it took some…coaxing. That coaxing involved a hammer, screw driver and pliers!

Once I get the header pipe back into shape, I put the exhaust on and tightened the bolts. Done! I fired up the bike and it revs noticeably freer. It’s also a fair bit louder. I wouldn’t say it’s obnoxious, but there’s a throaty note now that’s for sure. After a quick ride around the block, it seems like the jetting is spot on. It also starts up straight away, hot or cold. There is a slight leak where the header pipe meets the slip on, so I will put some red gasket glue there to seal it up.

So that’s it, all installed! Next up is cleaning the whole bike. It honestly looks like it’s just been sitting in a shed accumulating dust. And the area around the chain is bloody filthy, nothing a bit of TLC can’t fix. After that, it’s time to get out and ride the wheels off it.

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