Hayashi is right, my 750 engages that way too. If yours isn't working like that you might want to have it looked at.

 

If you spin the rear wheels to engage 4wd while the front wheels are stationary, you will break parts eventually. The control unit will make the 2wd/4wd servo drive forward to mesh the 3- pronged collar into the part will 3 recesses for the prongs. When all four wheels are rolling, there is little pressure on the prongs as they engage. If you are spinning the rear, with the front not moving, the prongs will have full load on them before they fully move forward into the recesses. They may take this a time or two, or just bend first, but they won't take it for long. This system engagement delay is due to the mechanical design, not electronic.

 

Thanks for your reply which was what I was looking for which is even if you can get it to go in by clunking and grinding itn't a real solution to this deficiency.

 

Check out my "Polaris 500 efi vs. bf650" topic a guy explained to me the whole thing.

Good luck