Never seen or heard of one till I bought this run.
As such the very first thing I did ( as with any impliment I have not seen before ) was to download the factory service manual and parts books.
When you don't know any better , following the written instruction can't do too much damage.
Oddly enough I have found quite a few "rebuilt" machines of different breeds where the shop has made a total mess of the job with wrong sized pulleys, tension springs working backwards or not fitted at all etc, etc.
And here is the relevant page for any who might be inclined to believe this white man speek with forked tongue.
View attachment 24533
By virtue of the fact the annual service is listed after the 500 hrs service one presumes GD intended these machines to be substantially more than 500 hrs/yr