so i just recently pulled my mower out of storage for the season, changed the oil and put gas in it and discovered the primer bulb didn't work so i used starting fluid and it started right up no problems runs as it should cut front and back grass. next week pulled the intake and primer bulb piece off and the gasket was shot, used gasket maker and waited till the next day and priming works so i started it up to cut and ran great but about halfway through i noticed a slight ticking but didn't think much of it b/c i was almost finished. after i finished i emptied the bag and went out to the front yard and when i went to pull the engine over something was really wrong, pulling the engine over it was like the conrod had shattered but the engine was still turning over and each revolution it got worse so i called it and tore the entire engine down to the crank case and the conrod screws were totally loose and figured this might be an easy fix so i gutted the engine tightened the conrod screws to 95 footpounds and the engine was totally locked up, tired putting out on it but still seized so i took the piston and conrod out and they are pretty badly scored after reassembling making sure the conrod isnt angled and everything is lubricated but when tightened the conrod seizes against the crankshaft. loose and everything spins fine. What went wrong here. was there not enough oil and got too hot? if so wouldn't scoring the conrod and crankshaft make it looser instaed of swollen and tighter? Are all i need is a conrod and maybe crankshaft? the piston looked fine just alot of carbon buildup.
Low oil , fuel thinned oil and water will all kill an engine
Most push mower engines are splash and have a dipper on the end of the rod to splash oil around.
These regulalry break off.
The surface that the rod runs on is polished mirror finish as is the con rod eye.
When it overheats little bits of rod weld to the crank so the smooth surface is gone and they bind.
Scoring in the barrel makes this worse.
The cheap & nasty check is to run your fingernail across the surfaces in both directions.
If it catches on anything they are toast.
#3
cpurvis
95 ft-lb is WAY too much torque for connecting rod bolts. You've probably ruined the rod.
When it overheats little bits of rod weld to the crank so the smooth surface is gone and they bind.
Scoring in the barrel makes this worse.
The cheap & nasty check is to run your fingernail across the surfaces in both directions.
If it catches on anything they are toast.
Piston and bore are perfect just a little discolored from heat im assuming also looking at the original oil that it was stored in winter and there were minimal metal shavings but it was very black and very thin. was this the issue?
i just also noticed the snap pin that goes on the piston was behind the governor arm in the sump. Did something else happen other than heat ive never seen such a sad engine like this before
#9
cpurvis
You might get by with replacing the crank and rod but I wouldn't be surprised if you find that those two parts and a gasket set will cost you almost as much as a brand new replacement engine.
Except in rare cases where the torque gun at the factory didn't get the bolts on the rod tight. All the other times like people are discussing here the bolts loosen up because the rod has overheated Most of the time factory loose bolts will fail within the first 5 mowings. the wrist pin clip being in the sump is a little odd. Have seen it before but in those cases it lead to a cracked piston skirt and failed engine.
If the bore is good and the upper & lower bushes are good ( crank to cases ) then go a new rod & crank.
They are not particularly expensive and readily available.
Double check the end float which is generally set by the thickness of the crankcase gaskets
