Load engine knock on 520

[johndeerefan]

Was raking hay with my completely restored 520 the other day. It ran great as always all day long. Shut it off in the edge of the field. When I went to start it it ran for about 15 seconds then the engine missed a couple of times and then started making a loud knocking sound, but had good oil pressure.

I checked compression and it was like it was when I overhauled it. Long story short, I thought it was a push rod. Pulled the valve cover, not it. Pulled the governor and checked it, not it either. I finally decided to pull the head. When I did I saw a piece of metal on top of the piston. Turns out a screw came loose in the carb butterfly and got sucked down on top of the piston. I have the worst luck with strange things happening.

Sorry for the typo in the subject line *loud not load. Text editor won't let me change it.

 

[Mike M]

As I was reading your message I was thinking of my reply to you and looking for a carb. screw was one of them. Then I read farther and you allready found it !

I had the same thing happen to a 620. Make sure you find them all if more then 1. IIRC I was able to get one out of the muffler of the 620 also. It also may of knocked and then quit after awhile too. The guy who owned it always took good care of his equipment and knew something was not right so he had me tear into it.

If you have never had the pistons out now would be the perfect time as I have seen many with high hours have broken top rings on the 20 & 30 series 2 cyl.

 

[johndeerefan]

Already had them out Mike. I did a complete overhaul to the tractor about 7-8 years ago and it only has maybe 100 hours run time on it. All of that usage time has been parades, rides, and a little hay raking.

 

[Machinery-Man]

Yep: That the down side of the hi compression set ups of the 20 and 30 series. I always put locktite on those carb screws, never had your problem...a real shame....show little things can mean a lot...those original pistons the aluminum alloys are hard to find maybe you can find some new old stock....

 

[johndeerefan]

Luckily it didn't mess the top of the piston up. All I am going to be out is another gasket set.

 

[Machinery-Man]

You may want to really check the side of the top ring for damage