I have a late 90's m-gator with the 3 cyl Yanmar diesel engine. My issue is that the top out speed of this machine is currently 7-10 mph. I cannot figure out where my issue is. I also have a newer mid 2000's M-Gator A1 and its top out speed is 25-30 so I know that i have an issue with the older one. Thanks in advance for any help!!!