WOW!! I forgot all about the work you did on your pipe, and all I have to say is: That bike better be a lot dirtier by now. Seriously that is a sweet write up and pictures. If I ever get going on making different sticky threads at the top of our section, that will definitely be in the exhaust section.

 

Well thanks, guys. Yeah, it's dirtier now and a lot of parts have been swapped since those pics. I plan on putting more thana few miles on her this weekend, so there's no sense in washing it now.

 

Iwent with a 340 kit with all the work performed at Thumper Racing. I have around 600 miles on the new motor, and I am very pleased with its performance.
Previously, I installed a HMF pipe made for the KLX250s. Fortunately, it works fine with the 340. I still use the stock carb, re-jetted for the the 340 and pipe combo. Sprockets are stock.
TR's Mr Hazel, who did the mods, had worked at Kawasaki, and is very knowledgeble about the technology. TR provides engine upgrades for all dirtbikes. Mr Hazel insisted a 300 cylinder be used which was available.
After break-in, it easily cruises 65 (although speedo says 70). The fuel mileage dropped to 50 mpg from 70 with stock motor. With different sprocket ratio it should cruise 75 easy (80 on speedo).
For horsepower, I started with 18, adding a ratio of 340/250cc, plus 1.5 for the pipe puts me around 26. It took a while to get used to the extra torque.
Most of my riding was in 105 deg summer heat in Texas and there were no over heating issues.
I hope this info is helpful. Good luck.
Frank