Front wheel lifting on climbs on my Mountain Bike I've got a full suspension XC/AM 29er mountain bike (Gary Fisher Hi-Fi Pro). I'm running a size small frame with an 80mm stem with about 7 degree rise.  Bike seems like a good fit for me. I do run the seat a touch lower than optimal for more room to move on sketchy sections (no dropper post) but still not so much that my legs scream on flats and climbs.

However on a lot of climbs, even ones that are not super steep, my front wheel seems to pop up quite a bit. This makes me have to foot down unexpectedly when the climbs are rooty or rocky. I try to get as close to the bars as possible when I'm digging hard, but I feel like something might be better done with bike fit than bike english.

What should I try to set up the bike to avoid this?  I switched from a slightly longer 90mm stem due to the feeling I was going to OTB on sketchy terrain, so I don't want to play with lengthening the stem much.

Things I considered:
Raising seat (would require a $$$ dropper since I'll need to lower it for sketchy sections).
lowering stem (I've got about 20mm of spacers to work with below the stem)
Flipping the stem (not sure what this will do to handling on steep descents)

What's going to be the most effective way to change the setup to avoid or reduce the lifting effect?
I had the same problem on a regular non-suspension bike on the road, if the slope is steep enough.  The main cause is technique, and its exacerbated by your suspensions.

As you push down on the leading pedal the bike wants to rotate the other way, like you're lifting the handlebars and pulling a wheelie.  Your suspension is probably acting as an amplifier for this.

This leads to decreased traction on the front wheel, so turning becomes interesting.

Main Solution is to pedal more steadily in a circle, rather than stomping down on the foremost pedal.
To a lesser extent, you can also:


Lock out the front suspension, or dial it down a bit in bounciness.
Move your body weight forward on the saddle, or get off the saddle completely.
Remove weighty things from the rear of the bike - I found moving my full water bottle to the forward bottle cage had a noticeable impact.  Consider moving toolkits etc.