Since the 200x and the normal hardtail ATC200 engines share the same top end...

[bobotech]

...why is the 200x so much faster?

The reason why I ask is that I posted asking if the 200x and the atc200 engines could interchange and they can but won't that make the 200x much slower using the atc200 engine top end?

[swampthang]

If im not mistaken the 200x has a little higher compression an a hotter cam than the 200 im not sure about the valves though if theres any difference.

[TheRealFatShady]

Not entirely, the gearing is different. The X has a manual clutch also, which arguable affects acceleration and somewhat speed I believe.

The cams are different, as is the carburetor.

[bobotech]

Ahhh. So it would be better if I were to put new rings and gaskets on my smoking atc200x engine rather than use the ready to go atc200 engine that I have currently?

That makes sense about the cams and compression.

[swampthang]

If you have a 200 motor laying around you can put that motor in and run it till you get your 200x motor rebuilt. Yes the 200x motor would be the faster pick.

[TheRealFatShady]

You can use the 200 cylinder/piston/head and just use the cam and carb from the 200X if you'd like.