Hi gavin351 and CJ,
The other main issue that causes this problem is a rail failure which misaligns the two halves of the clutch.
I must admit that it's rather strange to have a 3Hp motor on the 14 inch model, chances are it's not the originally fitted engine that's on it. I also suspect that it's a twin rail chassis and not the earlier solid deck machine that you've got.
My fears are if correct, that a clutch issue has arisen and that has induced vibration into the driveline, this has either unevenly worn the thrust pad which in turn would affect the alignment or even worse induced fatigue fractures into either the front or rear rail which is causing the engine not to sit perfectly solid, thus giving the clutch the opportunity to grab every so many revolutions.
As CJ suggested some good close up shots of clutch area and also the rails where the engines bolts down on the clutch side. Also a good shot showing how straight both the front and rear chassis rails are.
Without a doubt we'll nut it all out. Poetry in motion there LOL !
Cheers,
BB
BTW shouldn't this topic be called "Clutch not staying disengaged"
