Farmall Cub piston removal

[13fx]

So this really nice recently restored cub that was sitting for "3 yrs" is really starting to snowball one here. Since I was unable to remove the Governor cover without the governor coming along with it I have to retime the motor. Well.... I went to turn the motor over to TDC on #1 and discovered #1 has no compression at all. After more investigation it is the rings and not the valves so I'm going to pull the piston out. Can I pull and reinstall the piston from the bottom, or so I have to pull the head and remove/replace from the top?

 

[used red MN]

So this really nice recently restored cub that was sitting for "3 yrs" is really starting to snowball one here. Since I was unable to remove the Governor cover without the governor coming along with it I have to retime the motor. Well.... I went to turn the motor over to TDC on #1 and discovered #1 has no compression at all. After more investigation it is the rings and not the valves so I'm going to pull the piston out. Can I pull and reinstall the piston from the bottom, or so I have to pull the head and remove/replace from the top?

I have not worked on a Cub engine. My guess is the piston will need to come out of the top, there are not many engine configurations that allow pulling the piston and rod out of the bottom past the crankshaft. And secondly, the rings need to be compressed somehow to reinstall the piston.

 

[Jim Becker]

From the top.

 

[13fx]

From the top.

That's what I was figuring. My buddy Mark claims to have done a couple from the bottom only and with as frustrated as this Cub has made me I was kinda hoping for an easy way out. Ah well, guess I'll go through the valves too since I'll be that far into it.
Thanks
Steven

 

[47fivewindow]

So this really nice recently restored cub that was sitting for "3 yrs" is really starting to snowball one here. Since I was unable to remove the Governor cover without the governor coming along with it I have to retime the motor. Well.... I went to turn the motor over to TDC on #1 and discovered #1 has no compression at all. After more investigation it is the rings and not the valves so I'm going to pull the piston out. Can I pull and reinstall the piston from the bottom, or so I have to pull the head and remove/replace from the top?

Are you sure you are not 180 out? I have never seen rings so bad that the compression was zero.

 

[used red MN]

Are you sure you are not 180 out? I have never seen rings so bad that the compression was zero.

I am also wondering how he ruled out the valves as the problem? You can make sure that the valves have some lash and are not being held open but you can’t really tell if they are sealing. It is pretty hard to hear if the compression is not passing back out of the intake valve when your checking compression. I suppose a “leak down” test accomplished by putting compressed air in the cylinder would tell this.

 

[wh]

Are you sure you are not 180 out? I have never seen rings so bad that the compression was zero.

Bought a FARMALL H one time that had sat for around 5 years. Outside with exhaust covered. Winched it on trailer and rolled it into shop. Got to checking it over and used hand crank to turn motor. It took 0 effort to turn it. Had a mag on it and gas in tank from when parked. Dad was helping and said to see if mag was firing. Ran a point file thru the points and wire brushed the plugs. Sprayed the cylinders with starting fluid and just screwed plugs in by hand. Dad turned the hand crank about 2 revolutions and it popped. Sprayed 2 of the cylinders again and when he lifted hand crank it started and ran decent. We were very surprised. Shut it down and a few minutes later tried it again. Extreme difference in turning hand crank. Compression had returned. Tractor still here and runs perfect.

 

[13fx]

I have not worked on a Cub engine. My guess is the piston will need to come out of the top, there are not many engine configurations that allow pulling the piston and rod out of the bottom past the crankshaft. And secondly, the rings need to be compressed somehow to reinstall the piston.

I e pulled a couple out of the bottom, but never reinstalled them that way before, but I have pinched the rings with my fingers before to get them to compress enough

Are you sure you are not 180 out? I have never seen rings so bad that the compression was zero.

Poured oil down the spark plug hole, compression jumped right up. After pulling the head it is obvious that #1 and #4 were on the very bottom of the stroke. The engine appears to have been run pig Rick for quite a while and carbon has built up quite a bit. This motor shows signs of having been rebuilt not to many hours ago, but things were not done quite right. The cross hatching in each cylinder doesn't cross at all (it just runs circles).

 

[47fivewindow]

Keep us posted how it works out. Good luck.