Jacobsen Tri King 1900d - Loss of power

[gunnersmaj]

Hello. We recently bought a second hand Jacobsen tri king 1900d. Everything worked well for the first cut, but now the machine feels like it is in a limp mode. If you take your foot off of the accelerator, the mower no longer comes to a stop (as it did before). The top speed has been reduced, it hardly moves in reverse (and doesn't at all if it is a slope) and when you are going up an incline it sounds like the motor is struggling. Any help would be much appreciated. I believe we have checked all of the usual things.