I am kinda curious, what exactly do you look for setting up a suspension on a "dune" bike?....Polar-Bus
Think about all the riding you do in the woods and mx, then think about what percentage of that riding is in loamy/sandy conditions? Maybe 10%, that being probably high even.
Well in the dunes you are 100% in the most dragging, power stealing, non-suspension friendly environment known to two-wheelers. Your front tire cuts through the top 3-9 inches of sand like a pizza cutter until you reach about 15 mph where it will finally float on top.
So as far as suspensions go, the sand steals your first 3-6 inches of plush fork travel at speeds lower than 15 mph. Basically your front end is plowing the sand and compressing until you are up to speed, meaning stiffer springs than most riders and stiffer compression also.
When up at speed, now you have a ride that is stiff like a mx rider, but on the sand. If you threw nobbies on my KX5 and took it on the dirt it would be a bit harsh and stiff, not ideal.
Another way to look at it would be the sand is like an additional suspension setting for your bike and you have to adjust for it. It is soft so you have adjust stiffer to compensate for it.I think to sum up a dune two wheeler suspension to a MX one would be:
1. you need one or two up stiffer fork springs with stiffer valving to keep from plowing. Set the fork preload to highest (spacers inside the forks with the springs) and then slide the forks as far down the triples to help with steering rake. Makes a little crisper turning, if that is possible in the sand... lol
2. set the sag in the back like normal but the spring is one stiffer as well.
3. compression for front is stiffer to keep from blowing through the stroke too fast and handle the dune face entries. Try to keep the front from blowing through all the travel and bottoming out because that will take any control away from your steering. Rebound is a little less so the forks can return faster to keep from loading the travel on woops and for landing drops/jumps.
4. compression for the rear is stiffer to keep the tire in the sand for traction and when landing jumps since most all dune landings are 80% rear and 20% front. Rebound is a little less as well to help keep the rear in the sand for traction and steering, since alot of the turning in the sand is with the rear end and throttle.
Of course these are my findings and are not an experts set-up, just what is getting better for my style...
Sly