UPDATE PURCHASED MOTOR with 400ex carb, mod CDI, wiring harness, starter, kil switch, and other components. Now I just need an aftermarket Head Pipe!!! Help!

I have the opportunity to buy a 2003 GT Thunder modified 300ex engine with a National Kit. Comes with modified 400ex carb and CDI to match.

I have been searching all over the internet for information. The best match was something from DSI says 30% increase over stock.


I am placing the motor in an old 88 250x that used to run a 350x motor that smoked etc.

Anyone know anything about the national kit? How do these things run/compare to the 350x motor? I have heard close...


The reason I am not fixing up the old 350x motor is I want something new, dont want to mess around, like electric start, and I am just a weekend warrior so push button is preffered.

 

Also need a good header pipe. The 350x is dual, so I was thinking about fabricating the 2 ports into 1... Are all headers stock size in terms of bolting up to the engine?