Check the pto air gap. My 1810 was having the same issue a few years ago, would not engage when engine was hot. I found the air gap was too large. I set the air gap to .015", no issues since.
Here is the chassis service manual for your tractor:
http://www.onlycubcadets.net/forum/s...ad.php?t=25397
The pto troubleshooting section is very good, easy to do if you are somewhat handy with a voltmeter.