My A has had a dull thud knock for quite a while now. When I pull the plug wire on the right cylinder it quiets down and when I put a load on the engine it totally goes away. Does that sound like a wrist pin to you guys?
Easiest thing to do is to see if you can lift the flywheel. If the flywheel lifts ever so slightly its the crank bearing, try the same procedure on the pulley side. Otherwise you need to remove the S shaped plate that is ontop of the block between the flywheel and clutch and try to wiggle the rods.
I should've mentioned that I've checked that, sorry. No detectable up and down or side to side movement on the crank. I checked the main bearing clearances on both connecting rods, pulled a pair of shims out of one that was just a touch on the loose side. That made no difference. while I had the rods loose from the crank I tried to feel for any looseness in the wrist pins. They seemed ok but that's kind of hard to do a proper check with the piston still in the block. It's annoying as heck. I sure hope its just a wrist pin because I sure don't want to strip it all the way down. :lol:
Think the 46 A has the same problem. Its hard to describe I guess. You can hear it hammering, but it's not a sharp hammer persay? I need to investigate further maybe with a stethiscope and see if maybe I can pinpoint exactly where it's coming from. I was thinking it was wrist pin bushings, but I'm not exactly sure yet.
I'm not getting any noticeable movement on either end of the crank. Yesterday I did notice that my fan has a whole bunch of slop.....like two inches worth of slop. That has me wondering if maybe the sond is actually coming from inside the governor housing and telegraphing through all that cast iron.
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