Harry Bloomfield has brought this to us :
The tractor broke one of its drive /motion belts, in the process of
investigating that, I found another issue..

The PTO clutch driving the cutting deck is not fully engaging, I assume the
clutch slipping. I had an idea something wasn't quite right sometimes, when
asked to do a lot of work, but now I know its slipping when its supposed to
be fully engaged.

The PTO pulley/clutch is an MTD 717-1787A - this one..

http://www.ebay.co.uk/itm/14778-REPL...AMXQWzNSm~w 6

https://tinyurl.com/yb8gqz5b

Which is shown in the photo inverted. The small pulley goes uppermost, driven
all the time the engine is running. The lever coming out of the side engages
and disengages the drive to the larger deck drive pulley.

I have not got the unit off yet, to take a proper look at it, but wonder(as
these are quite expensive) if anyone might have refurbished one of these
clutch mechanisms?

The pan shaped part with the lever coming out, obviously remains stationary,
but I haven't yet worked out what prevents that pan rotating.

Er, forget that I think I have solved it...

I managed to push it under cover to work on it, turned it over a little
way onto it's side, to get a better look at the issue(s).

Even with the PTO clutch engaged, I could with a bit of effort turn the
PTO pulley in relation to the engine output shaft.

A very long bolt up from the centre, through the PTO into the end of
the crankshaft, then a very large but thin outer nut above that, which
was quite loose. I tightened the thin nut and the clutch appeared to
lock up fully.

The thin nut is clearly visible in the ebay photo.

The only thing remaining, is to work out how that thin nut is supposed
to be set, or how tight it is supposed to be. Plus of course waiting
for my replacement motion drivebelts to turn up.