Howard, welcome to TBN. On the Satoh, you might be best to post this down in the Mitsubishi/Satoh section of this forum. There are some real Satoh savy guys that frequent that section. Sounds like you need to do a compression test to confirm or rule out a serious problem.
I sell a repair manual for your tractor and we can offer troubleshooting assistance and repair parts. Call toll free 1-800-609-5110. Sounds like you have worn rings or a cracked piston. Bill - satohparts.com