1993 - 10520 Gold Series Knock / Rattle FIXED!

slackinoff

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I found the fix for my engine making a piston slap sound. The sound would start after running for about 10 min at full throttle. I have heard it before in the summer but it's more apparent in this cooler weather. At first I thought it was the exhaust ports, two of the three were completely plugged but it actually made it a bit worse after I cleaned it. New sparkplug made it a bit worse yet. But the mower has always ran great, starts easy and testing compression today it has 115psi of compression cold and a touch more psi hot.

I picked the mower up this spring and absolutely love it. I did a slight cosmetic restoration, repainting the deck, minor worn parts like new wheels, axle bolts and a new blade.

So for the high rpm knock, the thing that fixed it was the altitude adjustment screw on the carb. Opening it up (richer) immediately makes it go away. About half a turn from where it was making the kock. There is a video on YouTube of a guy who had the same problem and before he could figure it out, his threw the rod unfortunately. Not sure if he had a different problem, but it sounded just like mine did.

Just thought I would pass the info along. I'm guessing it's from spark knock by being lean, although it wasn't lean surging or showing other signs of lean mixture. Anyone else ever come across this problem? My only worry is that I hurt the rod or big and small rod bearings.
 
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