Cub Engine Knock

Anonymous-0 · Dec 5, 2010

Engine knocks near number 3 piston, lower block. Main bearings new and to spec. Rod bearings replaced and to spec. Number 3 connecting rod will move back and forth slightly on crank and wrist pin (side to side) but there is no up and down play . The other rods will not move at all. Before putting things back together, have I solved the knock?

Andrew Z · Dec 5, 2010

I would have a shop check out those wrist pin bushings for sure. At least it will give you piece of mind

Andrew

tomato frank · Dec 5, 2010

hello,it just so happens i just took pistons and rods out of a cub last week.the guy i got it from said about the same thing,except he thought #1 was the problem.well #3 rod was blue and the crank journal was wiped out.i would check them all.i will grind crank if possible or replace,as far as rods go i will recon or replace.make sure that you clean oil galleys well also.wrist pin bushing must be checked as well.there"s my thought on that. good luck

Owen Aaland · Dec 6, 2010

If you can not move the rods side to side something is too tight somewhere. On most engines you should be looking at somewhere between .005 and .015 inches side clearance. If you can't move it by hand it is too tight.

Anonymous-0 · Dec 6, 2010

Thanks for the advice. I have decided to run it for the winter and and check the wrist pin in the spring when it is warmer. I have a replacement radiator to put on at the same time. If it is a bad wrist pin, I don't think running it 5-10 hours will hurt anything.

Cub Engine Knock

Anonymous-0

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Andrew Z

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tomato frank

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Owen Aaland

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Anonymous-0

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