I think the 670 would have moved it quite easily. We have even seen 212 engines on that size kart, single axle though. But the liquid cooling will be a big plus though! What state are you in?
Yea, I bet it would get up and go with thr 670, but I think my top speed would be fairly low in order to get the right torque, especially with the large tires, two axles, and the diffs (they weigh a chunk). Most of the time it wouldnt matter, but in the dunes thats a different story. My worry is that I would have major issues on big hills, ones that you need a combo of speed and torque to get up. Plus I feel with the twin axles, there is some great potential for extra traction. Also, after joining a 670 forum, there seem to be a chunk of quality control issues, and little tweeks to get these to run right. I could do those, and dump more money into uprgades to bring out more hp, but it might be smarter to just get an engine thats already made for racing at that point. A sled would come with a CVT (which I havnt bought) and the Comet 780 (for the 670) set I would need runs $500 ish.
I have a line on a dissasembled 2009 Ski-Do 800. 800cc, 2 cyl, 2-stroke, pull start, liquid cooled. Owner says its around 160hp currently. Thinking a few days on it, but its a great deal. This would also have reverse.
I live in Western Washington, which is fantastic for hiking, walking deep into dense tall trees, but its not great for offroading, just too thick to go far. Ill do the bulk of my riding in Oregon, and some forest service roads in Idaho.
Here are a few good spots in Oregon:
If your willing to drive to the middle of nowhere:
-Christmas Valley Sand Dunes:
-Winchester Bay on the Oregon Coast: