Hello Nicholas
Well, that depends ...
If you intend to make this an every-week runner (your main mower)then
I would upgrade. The replacement engine should be an OHV though (much smoother).
The good think about an engine change is that it can always be
changed back to the original spec. (keep the old engine).
The old Kirbys were great engines and basic parts are available.
There are plenty of SB45 posts in these forums - enough reading
for many happy hours.
Hope this helps.
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JACK
