Which (used) mountain bike should I buy? (longish OP)

Okay, here’s the situation. I’m a total newbie to the sport of mountain biking. I want to buy a used bike, and I want to get a good bike. I don’t mind spending a little money, though I may wind up getting a new bike later on, when I have a better understanding of the pros and cons of various components and such. For now, I want to get the highest quality bike that is appropriate for me that can be purchased used.

What I plan to use the bike for is to ride various trails around the Los Angeles area. These trails generally involve lots of up and down sections. I’ve read that hardtail bikes are better than dual shock for this type of riding.

Also, I’m 6’1" tall with a 34" inseam. I’ve seen a few different formulas for computing the best frame size, but they all seem to average out to around 19"-21".

Here are some of the listings from Recycler.com for my area code, with my comments in italics below each one:

SPECIALIZED M2 Works, aluminum mountain bike, custom built, XTR front & rear, 19", 21 speed, Rock Shox, paid $600, sacrifice $200
Sounds like a dual shock, I’m not sure. The frame size is right, and the price is good

BALANCE mountain bike, completely customized & race ready, excellent condition, accessories included, $500
Need to call for more info…

RALLY M60 mountain bike, blue & white, low miles, like brand new, paid $450, sell $300
Need to call for more info…

kona blast mountain bike with platform peddles,excellent condition.color grey $400
I emailed this guy for more info. He said it’s a 19" frame and has 21 speeds

98 diamondback XC mountain bike, full shimano lx 8spd, manitou sx-r fork, 18’’ frame, tuned and serviced, in Glendale, click for full specs. $600
Extra Text ill regret selling it but with work and school i dont have time to ride anymore. original owner, well looked after, built everything on the dbr 7005 aluminum frame, icon flatbar, yetti grips, specialized S stem, sun rhyno lite rims, wtb velociraptors, shimano 8spd LX drivetrain and brakes, selle gel saddle, gt seat post, 2001 manitou 80mm sx-r fork (300 dollars alone): best fork voted by mtbr.com. rims are true and straight, brakes and tubes are new, had it serviced at Glendale Cyclery last week, have receipt and manual for bike and service. all together ive spent a good 1200 dollars on it. first 600 takes it. youll be hard pressed ot find a new or even used bike thats as good for my asking price.
Sounds good, if only by the length of the description. He sent me some pictures, and the bike looks like it’s in good shape. However, the 18" frame might be a bit small and the $600 might be more than I want to spend, even if the bike is worth it

Mountain Bike 21’’ IBEX with Disc Brakes,Shimano Components,Rapid Fire Shifters,Judy Front Adjustable Rock Shocks Great Deal Ridden Once! $499
Sounds good, need to call for some more info. 21" frame might be too big.

There were a few others that read something like “Mountain Bike, great shape, $75.” These ads lead me to believe that they are not serious mountain bikes.

I’m thinking the 19" Kona might be my best bet. Any advise or suggestions from experienced SDMB bikers?

I don’t think an 18" would be too small for you. Borderline, maybe. The diamondback sounds like a good deal if you can talk him down a bit. It sounds he really babied it. He knows every part. That’s good.

Konas are good bikes, and $400 is a good price.

The Specialized M2 is a hardtail, XTR is cream of the crop gear. $200 is a steal. I’ll bet it’s gone already.

I think your approach is sound - get a decent first bike then figure out what you really want.

I don’t know how heavy you are, but if you are heavy you probably want to stay away from the feather-light aluminum and Carbon-Fiber racers. The M2 might fit into that category.

I’ve had good experiences with Trek, Fisher, Specialized, and GT bikes as far as starter-type models go. They’re kind of heavy but they take abuse, they don’t fall apart, and they shift well. In your area I don’t think disc brakes are an absolute necessity as it’s relatively dry and you probably won’t need the stopping power for a while. Rim brakes should be fine.

Go to some bike stores and try a 19" Kona and 21" IBEX. You’ll never know if it fits, otherwise. You can’t assume that because you’re 6’ 1", that it will fit.

You might want to think about the rear shock. I can “switch out” of mine - turn it into something that resembles a hard tail. It is easier to ride roads and uphills without one, but it is always more comfortable with one, and you will be less prone to bounce out of your seat.