I have a 4 wheel drive MX4700, i broke the valve stem off and couldn't find one like the original yet, so i used one i got at O'reilly's and i'm having a hard time getting the tire to seat on the rim,any ideas?
I use a 2" wide ratchet tie down around the circumference of the tire, and tighten as tight as I can get it. Usually that gets it close enough to the rim for the air to go ahead and fully seat the bead.
If I understand correctly you are having trouble getting air into the tyre faster than it escapes. Try temporarily removing the valve from the stem until it seats. And maybe you have another attachment you can put on your air hose that lets air in faster than a normal inflating nozzle. (For example an air blasting nozzle.)
Also try laying the tyre down whilst the rim is supported up off the ground so that gravity is helping push the tyre down against the rim. (Or alternatively support the tyre whilst pushing down on the rim.)
Just a little squirt of ether/starting fluid into the tire and pass a torch or wad of burning newspaper by it and it seats itself presto. You don't need much ether.