I would use a 6 paddle tire for dunes.The 8 will put to much load on the engine.If your bike is jetted prefect I would go up a size or two on main jet for the dunes.You'll be running alot wide open out there.Put a little more premix in your gas minimum 28:1.
I'm with '02 CR Rider, go with the 6 paddle if you must have one. The 6 paddle will spin a little more, but that will really help being on a 125. I hope the dunes you're going to are mostly flat because they aren't kind to 125s or any smaller dispacement motors for that matter. If your dirt tire is in good shape you might even run that instead of getting a paddle. It takes a little longer to get up to speed, but it won't be as hard on the bike. The only time you'll really notice a paddle is when hill climbing and approaching rutted jump faces. The paddle tends to track a little straighter and keep the rear end from dancing if the sand is torn up. For jetting I raise the needle one clip and run the next larger main jet. If you try it, let us know how it works out.
clip was already on the second notch, raise main jet up one, running 6-paddle tire, engine sounds like a screamin banshee, plug looks alright, yes it did straightin out the ridding for the real wheel, i can go straighter now than before, but miss running down caliche roads and stuff, oh well, it was worth a grin to try, thanks for the repsones