KDXRIDER.NET

Can anyone here tell me if any of the 200cc 2 stroke scooters (Vespa,ps200,ect) with the same bore and stroke measurements and a 16 or 17mmpin size could be modified to use in a kdx to add stroke?? How does Eric gorr racing get them to 240cc?

If a liquid-cooled KDX200 or KDX220R is bored to 240cc, there is no power valve sytem, as best I remember.

He offered a 223cc bore and piston at one point in time.

69mm 216.8cc or 70mm 223.2cc is the most you would want to bore a 200 out to, or a 220 out to the 70 mm size.

I much prefer the 69mm so that you can have the A, B, and C size incremental pistons to compensate for bore wear. Wiseco is the only one making a 70mm piston. Wossner makes a forged piston with coated skirts in 69.00mm A, 69.01mm B, & 69.02mm C sizes, so I recommend them the most in order to have the best piston to wall clearance for the entire lifespan of the cylinder.
Once the cylinder plating gets worn over time, the piston will rock a bit more back and firth with the looser clearances, and accelerate the wear further. Being able to run a B or C-sized piston to compensate for wear will extend the useful life of the cylinder a bit as well as the lifespan of the 2nd and 3rd replacement pistons in years to come, as they won't be rocking loosely in the bore as much.

All that being said, I picked up a fairly well ported 220 cylinder that was bored out to 223.2cc 70mm, so I will be modifying a cylinder head to match the 70 mm bore, and running this one at some point as well.



240cc as it was stated is bored out to the point where you lose the main exhaust port power valve. On an 89-94 200 cylinder, you can only go from stock 66mm up to 67mm or 68mm, as on those years, 69mm 216.8cc "220" size cuts into the power valve area, so you have to weld up the cylinder and abandon the main exhaust power valve. Not worth it in my opinion.