I recently bought a 1999 Bobcat 873 with only 750 hrs. on it. The previous owner said he bought it brand new and never used any attachment other than the bucket it came with. I detached the original bucket and attached a grapple bucket, but I can't get the auxiliary hydraulic system to function properly consistently. Sometimes the grapple bucket will open and close, but most of the time, it will only go one way or the other. I'm prepared to take the Bobcat to a service shop, but I wanted to try my luck here because I think the problem may be something simple. Does anyone have a clue what may possibly be happening here? Any thoughts and ideas will be greatly appreciated. Thanks.