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2016 kx250sr af

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    --Putting it Together for the First Time--

    Alright, now for the first time, we had the airbox working and electrics all wired up and mounted, now I could put this thing together! Here are some pics of it put together for the first time, what a feeling that was! While it looked like a work of art, I had a sea of problems with the set up on the first test ride, which made me realise this thing most definitely wasn't a finished bike.

    - The exhaust was not fitting clean to the engine manifold as it was still hitting the front frame rails, hence would leak carbon like there was no tomorrow.
    - The bike was jetted terribly, which made me realise stock jetting (and PC recommended jetting) for a 250cc was definitely not going to fly for this big bore 270cc cylinder.

    One good thing I realised when bolting everything together is that both the OEM and Pro Circuit silencer bolted straight onto the 2016 KX450f subframe with no mods. Only downside is that theres only one hole to mount the pipe on the 450 subframe, and for the 250cc silencer you really need a second mount. I'll get to how I tackled this in a later post.

    In summary, while it looked cool and could fire up, this thing was by no means race ready.

    This is not the last post! More to come to fix the above issues and to further pimp this ride
    Last edited by Danny; 05-15-2020, 10:43 AM.


      --First Ride--

      While it was an awesome feeling to get out on this bike for the first time, I couldn't really do more than 3 laps with out either:
      - Complaining about jetting.
      - Complaining about how slow the bike was.
      - Pulling off to put the air boot back on as it kept slipping off despite being screwed tight to the carb. There was just too much unnatural tension between the air box and the carb pulling the air boot apart.

      Now the air boot slipping off is a serious problem if not fixed, as un-filtered dust during this time was going straight into the motor. After this happened twice I didn't think twice and just packed up and went home knowing this whole "lowered air box thing" was not gonna fly, I needed a better solution.

      Upon inspecting the cylinder through the exhaust port when I got home, the piston was already so bad I actually had to replace it. Yeah, a custom size 270cc piston replacement in 1.5 hours riding... School fees I tell myself. Luckily just the piston was scored, and the cylinder luckily seemed to be ok as it was steel sleeved during the bore out.

      Taking the cylinder apart I also realise that the right power-valve would not fully open and turned out I had installed it incorrectly, while this was a quick fix, the jetting was still terrible and needing attention.

      More on how I fixed the jetting (and power valves) in addition to the air box in a later post.
      Last edited by Danny; 04-19-2020, 11:52 AM.


        --Fixing the Airbox--

        After considering the the airbox plate, I started to look at carb mods to potentially extend the carb back to the boot, instead of bringing the boot forward as it looks as thought there wasn't too much room for the boot to clear the shock if it moved any further forward. After doing some searching, I came across a local shop called TD Hatrick (, which sell carb parts and adaptors. They have a wide range of carb extender adaptors for all sorts of carbs. After searching around I bought the longest adaptor they had to fit the 1999 carb (60mm extension), knowing I could trim it down if needed.

        When it arrived all I needed to do was press the adaptor onto the carb as it was an exact fit and it was just long enough (had to use an actual press. I have put another 15+ hours on the bike since installing this part and is has been working perfectly. Only thing I needed to do was to seal the adaptor with DevCon to make sure the passage between the boot and the carb was airtight. See link below of the part I purchase to fix all my problems - best $28 I have ever spent.


          --Fixing the Power--

          Fixing the power-vales fixed half the problem, however it still just felt like it always had more, especially up hills it had a feeling like it was starving of fuel and would blubber. After pulling the carb out I noticed this thing was running lean with a 158 main and a 52 pilot jet. So one weekend I went to the track with my full stock of jets, and kept working my way up on the main jet until I found the sweet spot. Turns out this big bore drinks the gas, as it felt best running with a 175 main, 17 up from what I first found in this carb. I tried mixing it up with the pilot jets but ended up going back to the 52, it just felt better when in the corners or slower areas of the track. It might be different for other riders, but this combo worked best for me.

          In summary - updated jetting for the 270cc:
          Main: 175
          Pilot: 52

          I cant believe how much of a difference the jetting makes to these bikes, quite literally went from the slowest 250 I have been on to something that out powers any 250 on the track as far as I can tell. When this thing is ready for another piston I would seriously consider boring it out further too.

          Here are some pics on the track before the next big revamp on the suspension which I'll go over in another post. Engine working perfectly now.


            --Updating the Front End--

            Now everything was feeling good engine wise, I thought it was time to take it to the next level and update the front end by anodizing the forks and bolting in XTRIG ROCS triple clamps. I also got the holeshot device anodized dark red to match the triple clamps. Since I had a fork seal driver and fork oil on me, I decided to just order OEM seals and do this one myself once I got the forks back from the anodizer. Looks and feels awesome. After one ride I decided to go with the lower 821 fatbar bend. Almost exact same bend and the twinwall 999's, just in the Fatbar style.

            ​​​​​​​Here are pics of all the parts ready to go and afterwards all bolted on


              -- Anodizing the Rear Shock--

              To match the front end, I also got the rear shock anodized and also used the opportunity to respray the spring. I did this the proper way with 2-pac paint, using OEM green we had mixed up from an older build, hardener and I also added 5% by volume of FlexAid - this stuff allows the paint to harden while also retaining flex, perfect for springs and stops the paint cracking over time.


                --Finishing touches--

                To give this bike the factory finish I really wanted to get a carbon look silencer, similar to the ones Carmichael ran from 2000-2001. As that is literally impossible to find, I took the canister to a place called Dipit Kustoms, who specialise in hydro-graphics. Cant believe how good this thing turned out. While I do have a Berg clutch cover for this bike, I decided to also get the stock ignition cover carbon hydro-dipped to see how it would turn out. I have been on few rides with these parts on and zero troubles with marking this stuff, its bullet proof - - Dipit Kustoms killed it.
                Last edited by Danny; 05-15-2020, 11:21 AM.


                  --Finishing Touches Part2--

                  I decided to give carbon fiber casting a go and casted my own front engine mounts and chain guard using a smooth peice of alloy to cast those bits, then the original plastic rear disc piece as a mould for the carbon rear disc guard.


                    Click image for larger version

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                    Ok, no description needed here - This is her in all her glory, ENJOY.

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                    Last edited by Danny; 05-15-2020, 09:44 PM.


                      --Photo Time--

                      Some close up photos and another on the track after the suspension mods Click image for larger version

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                        Amazing project


                          Hi, Just got added. Here is my latest build. 2021 KX500