This month I have been spinning laps on the KX and really getting comfortable with it. I’m starting to feel right at home on the 250F now that I have got used to the power and characteristics.
It is a fun bike to ride and handles really well. Holding it flat out and throwing it around a motocross track is loads of fun. The bike is holding up well. Mechanically and cosmetically the bike is as good as new.
The Kustom MX graphics kit is still looking schmick and so is the Topline Upholstery seatcover. The Bridgestone tyres are still performing well. The front is mint while the rear is showing small amounts of wear but still hooking up as well as a new tyre.
The original chain has stretched and needed adjusting a few times. It is slowly but surely getting close to the end of its working life but the sprockets are still looking in perfect condition.
On my last ride I somehow managed to break the plastic skidplate bolted to the bottom of the frame. I don’t remember hitting anything to break it. I didn’t case-out the thing but somehow it broke.
It is made of a solid plastic and would usually require more than roost to break so I’m surprised. I have replaced it with a new one and I’ll see how this one goes but I’m not expecting to be breaking them on a regular basis.
Apart from spinning laps I have modified the silencer to make the exhaust gases flow better and make the bike more responsive. To perform this mod I had to remove the exhaust pipe and disassemble it. I then had to use an oxy-acetylene torch to heat the flutes in the silencer core and then bend them back in so they are no longer restricting the silencer.
The flutes were added to make the KX quieter but, unfortunately, restrict gas flow through the core. With them removed and the airbox opened up, together with the 2011 KX250F header pipe we fitted last month the KX-F becomes much more responsive, with a stronger power curve. The down side to these mods is that the bike is louder but not by much and still nowhere near as loud as an aftermarket exhaust.
I have been planning to re-valve the suspension but have wanted to get used to the bike, break in the fork and see how it performs in as many different circumstances as possible before re-valving. I believe I know all the ins and outs of how the standard valving handles and I feel it works very well but I would like it to be slightly stiffer in the initial stroke. I like how smooth it is and I don’t want to compromise that so, next month, I will re-valve the suspension to stiffen the initial part of the stroke without changing the rest of the travel.
Technical Editor Mat Boyd
HOURS: 20
MODS THIS MONTH: De-restrict silencer
MODS NEXT MONTH: Re-valve suspension
This long term update appeared in ADB Issue #449 – February 2017