KX500AF pipe needed!

[Sandblaster]

By kxpegger

Re: KX500AF pipe needed!

My 2008/2004 Service Honda uses a modified CR500 pipe and silencer built by FMF. The FMF P/N's for Service Honda were 04/122000 for the pipe, 03/09 122001 Power Core silencer and 3/20/07/122002 for the Turbine Core Q silencer. While Service Honda was building the the AF's FMF would not sell the pipes directly and had to be purchased through Service Honda. Now that Service Honda is no longer in business FMF may be willing to sell directly. The pipe is just a CR500 pipe with the KX500 exhaust flange head welded on. The silencers were also CR500 but with about an inch longer mid-pipe. I don't think it's really necessary to have the modified CR500 pipe and silencers from FMF to work. The KX500 exhaust pipe flange which can be welded on to the CR500 pipe would not be too difficult. The rest I'm sure could been done using standard CR500 silencers with a fabricated slip-on mid-pipe extension or some creative mounting adapters to the 2008 KX450F frame and subframe.

[Salt Lake K5 Guy]

KXPegger,

I own a KX500AF as well. Mine is on a 2008 KX450F chassis. I run FMF on my standard KX500, and have always been a fan. The AF, however, is sporting Pro Circuit exhaust of the CR500 origin. If you need any pics of it, I’ll try and help. My head is out getting plated, so it’s not in one piece at the moment. The guy who owned this bike before me did a “sorta ok” job on the pipe, but I plan on scrapping it and doing a better job on a new pipe. The gist of it is that he cut off the “female” style pipe end from the head side, and welded on a “male” style piece from a donor KX pipe. It also required making 3 spring loops for the tension springs. Further down the pipe, if you use the original coolant passage from the water pump to the head, you will need to dent the back side of the pipe a little bit for it to have enough room. I recommend using 19mm aluminum tubing behind the pipe, slightly flattened in that area, and flipping the coolant inlet on the head upside down. Tie it together with a piece of 180 degree bend silicone hose. I do the water pump side clamp with a very short piece of hose and a thermoplastic shrink wrap style hose clamp. This makes the need to dent the expansion chamber so severely less of an issue. I don’t like this dent because it is in the critical shock wave reflection area of the pipe, and small dents matter more here. You have the option of changing the water pump style, and running the coolant line further aft, under the pipe, and relocating the coolant inlet to the back of the cylinder. This is a lot of work though. You can find examples of this elsewhere on this website I’m sure. Check out TSR Products out of Australia for another example. Further back the pipe, the former owner also dented the pipe so the kick start lever would stow all the way. I plan on cutting a curve into the new pipe instead. The dent looks restrictive, and is right at the choke point on the exit side. You will have to fabricate a rear mount to your frame as well. Some angle aluminum to the rear subframe bolt works well. As far as the silencer goes, I used a CR500 one there too. I had to cut one hangar off of it, carefully, and move it to another spot on the housing, and weld it back on there. If you’re making a new pipe, don’t buy a plated one. They are horrible to weld. If you are going to have it plated or coated, do it before you run it.
I’m planning on experimenting with making an adapter for the head KXtoCR style, so I don’t have to cut up the CR pipe, but I don’t know yet if it’ll work. I’ll post it on here at some point.
Like I said, if you need any pics of how mine is set up for ideas, let me know.

Good Luck!
Brent.