Bike for experienced rider

Been out of off road riding for 5 years. Been riding the BMW on the street though. Want to race in Old Timers Motocross, maybe trail. Son has a KLX-110 (California green sticker'd). Older son may ride whatever bike I get (very fast motocrosser).

1) your physical size--6'2" 205

2) How physical / aggressive are you ? ---7/10

3) what do you plan to ride- MX tracks, occasionally desert / dunes / trails / Baja Mexico

4) Do you have any riding experience? Yes, riding since 10-ish. Last bike was a Yamaha YZ400F.

5) Do you think you will race ?--- yes, vet class, intermediate. Oldest son, fast bike class.

6) Are you mechanically inclined and will you be doing your own bike work?--- yes

7) Do YOU have a preferance to a brand/ motor choice (2 or 4 stroke)?--- Loved the Yamaha, Honda just because (don't like headshake, though), Kaw, Suk, Husky, KTM, et al. Probably 4 stroke.

8) Do you have a dealer close by your home that you might use and what brand(s) does he carry? ---Everything... this is southern California!!

9) How much ($) do you plan to spend on a bike?--- ???? don't know. No pieces of junk, no brand new 2010 YZF. Thinking 1 to 4 year old newish bike (lots of dealers with 2007/2008/2009 bikes brand new).

10) Do you live in California? --- Yes

11) Your age? --- 48, oldest son 21, youngest 10.

12) anything else that you think would help form an opinion- the street legal KTM 530exc and Husky 510TE sound awesome... but WAY too much money. Not many used to choose from. Foo foo bikes like DMZ / WR/ XR etc, not really interested.

Thanks, all, for the replies.

Yes, a pure trail bike won't handle MX, but an MX bike will handle trails, just not ideally.

Thanks for getting me up to speed on the MX bikes. I didn't know anything about 2009 Honda issues. The 2009 Yamaha sounds awesome and I'm not afraid of a carb ! (still have boxes of jets/metering rods for the carb).

They've got a brand new 2007 RM450 Suz. at Escondido Cycle for about $4500, plus some outrageous "setup" (profit maker) fees. Only 4 speed tranny, which may not be good for trails. Anything "bad" about this bike, if I could get it for under $4000?

Also, found a 2005 Honda CRF450 with almost no miles, sat in a garage, at Clairemont Cycle in San Diego. Wants $2600. Thoughts? It has some corrosion on exposed metal, so it must have been stored by the ocean (my guess anyway).

Called on one Kaw 450F, with low hours... except the guy hit a rock and broke the engine case... and then welded it???????

I'll keep looking. The KTM two stroke (and Service Honda 500) seem too expensive. Don't like the pre-KYB Husky suspension.

My son just got the Husquvarna 510TE. The dealer is prepping it for off road as we speak (remove throttle stop and air cleaner restrictor, catalytic converter, charcoal canister, O2 sensor, reprogram fuel injection computer).

Gotta get a couple of non-DOT legal tires (Dunlop K695's or similar). Then off with the LED taillight, turn signals, rear view mirrors, and headlight (to be replaced with a number plate).

Think we'll be ready for a warm up day at the track.