Hello Wallypat

I'm glad the clutch is working fine.

Spark Plug
Your 450589 should have a Briggs 80202 Motor.
To confirm this, please tells us the Model, Type and Code numbers located on
the metal air cover. Similar to this:-
[Linked Image]

Backlapping
Remember, backlapping is not a substitute for grinding, but an edge maintenance
procedure, meaning: the reel and bottom blade must be in relatively good condition.
A couple of photos would help, if you would like us to comment.
[Photos looking from above and below the front roller are helpful]

I attach instructions for backlapping from Richard Jones of the UK's
Old Lawnmower Club's Grassbox Magazine 85 of 2013. It's a good, no nonsense,
practical guide to the method.

We do not have a video for backlapping Model 45s.
Here is a short video of a professional unit being backlapped:

[video]
[/video]
[Linked Image]

Attachments
olc_backlapping_gb85_extract.pdf (811.86 KB, 8 downloads)
BACKLAPPING INSTRUCTIONS