Doyles bike was 250 (not stroked), won the 250 class against WRs et al. Impressive figures even if it was fully modded, and all pre 4 stroke hype, circa 2000.

 

It's not that complicated, and I can assure you, there was not countless hours of R&D.
They're all pretty much the same, and either 1 1/4" (stock), 1 3/8", or 1 1/2" header, with a glasspack. The FMF has the powerbomb gimmick.
My mig skills are excellent, my tig, not so much, as I don't get the practice anymore. SS is easier to work with than mild steel.
If I had a bender, I would bend one up, I may end up buying J-bends, and doing it anyway.

 

That makes sense.
Don't know where I got the idea it was a 300.

 

FSW header update: After having the header sit around the garage for many months I finally called up Jerry at Four Strokes Works and we had a nice chat over the phone. He said he suspected that the bend on the pipe was just a bit off and asked if I could send it back to him for some investigation. So I packaged it up and mailed it back to Hesperia, California. A couple or three weeks he mailed it back with some instructions to the effect that it had been re-bent slightly and that it fit fine in his jig, but that I might have to do some gentle adjustment to the oil pipe with light taps by a plastic mallet. Hmmm... He also said that mounting the KLX300 muffler to the 250 frame would require a 6mm (three washers) spacer for one of the bolts. He was right there. So I mounted it up and, lo and behold, it still touched the oil line, slightly. I tried his suggestion of tapping the the oil line with a soft mallet but it didn't budge. What did work, however, was to get some channel locks, pad the jaws with a rag, and ever so gently BEND the oil pipe to give the clearance. First I loosened the nut where the pipe goes into the engine on the right side of the bike, below the header, then put a small bend in the vertical run of the pipe over on the left side. Worked great. The pipe bends pretty easily and I now have about 2 mm clearance at the header. There's still not much room though, the header only clears the frame by 1 mm or so, but it clears. With the KLX300 muffler and that nifty endcap it sounds positively righteous. Maybe a bit too loud though for riding in sensitive areas, like down in Moab, but for for dedicated ORV parks I think it will be just fine. I haven't gotten out for a good road test with this new set up (it's freakin' snowing today here Northern Utah) but we're heading for the desert tomorrow (Knolls, if you're local and wish to join us) for a good ride. Current jetting a 125 main with the clip on the needle in the middle groove, and a 38 pilot. Might sound lean but I'm at 7000 ft. We'll see how it goes. With the stock exhaust and some airbox mods, including a UNI filter, a 122 main and 35 pilot worked well.

Here's some pics:

Header from the front

Header from the rear

Groovy muffler endcap

Area of the oil pipe bend