loud metallic scraping noise after blade change – Honda HRD536c (1998) Roto-Stop issue?

Jules

Forum Newbie
I am having a strange issue with my 1998 Honda HRD536c lawnmower after replacing the cutting blade.
The issue:
Immediately after installing the new blade, the engine block completely seized/locked up when trying to pull the starter cord. I took the blade off and remounted it carefully. The engine now turns freely by hand, but when I start the mower, there is a deafening, metal-on-metal scraping noise.


What I have already verified:
  • The blade mounting bolts are not too long and are not catching on anything.
  • The blade itself rotates freely 360 degrees by hand without hitting the deck.
  • Before the blade change, the engine ran flawlessly and was completely quiet.
I am having a hard time finding the exact schematics or information for this specific older model online. The mechanism has a very prominent, centrally visible spring in the middle of the clutch assembly (as shown in the attached picture).
Since this model features the Roto-Stop (Blade Brake Clutch / BBC) system, I suspect that something shifted out of alignment.
Has anyone seen this specific "visible central spring" variant before, and what usually causes this extreme scraping noise after a lock-up? Could a misplaced washer or woodruff key cause the clutch assembly to drag permanently?
Thanks in advance for your help!


 

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