Top speed is not what a dirt bike is all about, it is how quick they are. With the broad range of displacement (cc's) and the 2 and 4 stroke engines, there really isn't a good answer to this question. I have a 2 stroke 200cc and a 4 stroke 525. The 200 will top out around 65 while the 525 somewhere around 95, yet in the woods, the 200 is quicker.
Unleaded pump gas. I run 91 octane in my 525 KTM.
For professional motocross, the biggest bike that is allowed to be raced is a 450 four-stroke. For local race purposes there is a Vet class that allows any size bike to be raced (usually up to 525 since that's the biggest motocross bike that KTM makes).
I ride a 07 525 XC-W and the manual recommends Motorex Power Synt 4T (or similar synthetic) with a viscosity of 10W/50 or 5W/40.
not fast enough
It all depends i ride both but i bought a 2006 polaris 330 magnum ATV and it does any ware from 45 to 46 but its and automatic and i own a 2000 Honda xr 100r this is a manual with a clutch. but the dirt bike has a smaller engine but its lighter and has gears giveing at a top speed of about 70 -80 mph but how ever there are ATVs that are built for speed like the polaris outlaw or polaris predator the outlaw goes 90 mph and this is a very fast machine but its biggest cc is 525 so if u raced a 525cc dirt bike vs the outlaw 525 it would be close but the dirt bike would win because its lighter and the outlaw is a manual to with a clutch but it only has a benifet raceing dirtike from a 300 cc or lower so to awanser your question dirtbikes are faster they are built for speed and atvs are build for a bunch of stuff such as trail rideing working hunting swamping mudding or just having some fun
It Clocks 76mph
525 meters per minute equates to 19.57 mph
With stock gearing in the 90-100 mph range.
The Polaris Outlaw Is More fast
In the trunk on the right hand side. You can pull out the panel to see it.
The BMW 525 was introduced in 2000. It was made until 2003 and then it was replaced by the BMW 525i E39. It cost around $25,000 new and a used one is $8,000.