I run a zStart Pro Rekluse clutch. The Rekluse clutch is the single best modification you can do to your YZ for the woods. Just because you have a Rekluse does not mean that you never touch the clutch. I set the clutch to engage immediately off idle and while riding in tight/gnarly stuff I am constantly working the clutch to smooth things out, control wheelspin, etc. The nice thing about the Rekluse is that the clutch pull is much easier, plus you have the added benefit of not having to be perfect 100% of the time. The guys that suffer flameouts with the Rekluse are the guys that never touch the clutch lever.
Regarding the Rekluse setup, there are two attributes that can be tuned; the engagement point, and the engagement rate.
Engagement point is the RPM at which the centrifugal mechanism starts to bring the clutch plates under pressure. This is controlled in both Rekluse designs by changing the return spring pressure. Heavier springs make it engage at a higher engine speed.
Engagement rate is how quickly, in terms of how many RPM's gained, the clutch goes from starting to engage to completely locked up. That's adjusted by changing the amount of weight used in the clutch, be it wedges or balls. More weight makes it engage more abruptly.
I set mine up to engage immediately off idle, but I set it up to engage at the slower rate (using fewer balls in the Z-Start Pro). This can be done with the EXP design by using some or all of the lighter supplied wedges. The result is that I basically never touch the clutch lever regardless while moving or trying to move through tight spots, loose climbs with ledges in them, or much of anywhere else. All clutch control is done with the throttle, just like having a manually shifted automatic transmission. Only use the lever for standing still blipping the engine, finding neutral, stuff like that. No flame outs, except for the occasional panic brake stomp, and that doesn't even kill the engine most of the time.