2000 yz engine size confusion

Hey guys I'm new to TT, and to larger engine 4 strokes. I just picked up a 2000 yz426 for a pretty good deal, but I was doing research on vins and stuff and according to the vin on the bike, it's in the 200-249cc range... But on the engine casing it says 426cm cubed... The owner also said it was 426... Probably a stupid question but, I'm presuming to trust the actual engine casing since the blog or page I visited may have been wrong or something. Just wanting to be sure I didn't get ripped off and to be sure I'm not uninformed about my own bike. Helpful response will appreciated to ease my worry about this. It feels like it's bigger than my '99 cr250 power wise, but I tend to over think things

Possibly that year used the same frames for 250 and 426?

It could be that someone put a 426 engine into a 250F frame, but if they did I would suspect that there would need to be some modifications to the frame and they should be evident if you look closely.

Ok so what should I look for if it is a different frame? Mounts welded on or something like that?

But also am I correct that the engine is 426 from checking the casing?

Yes, look for signs of motor mounts being moved.  If the cases say 426cc then I'm sure it's a 426; the cylinder and head on the 426 are substantially larger than a 250F and the 250F would feel way underpowered compared to your 250 smoker.

Ok I'll be sure to take a look at that. Yeah, it's definitely not smaller it could keep up with my two smoke easy and probably beat it, I've only taken it to the track once so far. Thanks for the help cowboyona

Actually, the steel frames, etc., are nearly identical between the two bikes, and the engines are so similar in appearance that when the 250F was being developed in 2000, Doug Dubach rode it in the 450 class.  Nobody said anything about it being a 250, and no one ever knew the difference. (except maybe in wondering what it was that made it rev like that.)

If the VIN number indicates that it is a MY 2000 then it must be a 426, the 250f did not come out to the public till MY 2001. 

Thanks so much for the help guys

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