Cub was running great, pulled into shop and painted and cannot get it started. Checked timing and spark, all OK. Fuel leaks out of carb. bowl when I loosen plug. Used starting fluid and engine just turns over, not firing at all. Pulled #1 and put finger over plug hole, cannot feel compression. Need some suggestions as to what is causing problem. :help:
Lost Compression
- Thread starter rstoots
- Start date
Think I found the problem but don't know how it happened. Pulled hood and spark plugs, did compression check, #4 @ 75lb all others at 0. #2 and 3 plugs were wet with coolant and plugs were corroded, valves were also corroded, #1 and 4 were dry. Squirted oil into cyl to lubricate rings and valves, no help. Cleaned plug reinstalled, still no start. Looks like I need as a minimum a valve job. Won't know until I pull head.
Hi,
Too bad that happened to the engine.
When you remove the head, clean it well, and check it with a straight edge, and see if the bottom of it is flat. If it is warped, it should be flattened at an engine shop.
Check the head and block for cracks. They can be small.
The people on here like to use Permatex Copper Spray on the new head gasket, before putting the head on the engine. It helps it seal well. Spray both sides of the gasket, just as you are going to put it together, and put the head on before the Copper Spray dries.
Use an even application of the spray on the gasket. Practice a little on some flat metal, if you have never used Copper Spray before. I think they sell it at NAPA.
When you put it together, the head bolts should have NON hardening sealer put on the bottom 1/2" of the threads before putting them in. The bolts go into the water jacket, and water can run up the bolt threads without sealer. tst has said this on here too, he rebuilds many Cub engines.
I use Permatex Aviation Form A Gasket, it is a non hardening liquid. It comes in a small can. They have it at NAPA here in the west US. If you buy one, stir it well, down to the bottom, before using it, it settles in the can sitting.
Before putting the head on, I would turn all the bolts in the holes by hand, without the sealer, and be sure they turn easily. Then remove them.
They have to turn easily to get an accurate torque reading. Use a tap in the holes to clean them, if needed, and a die on the bolts, if you didn't buy new bolts.
When it is together again, I would wait a day before putting coolant in the radiator and engine, it will let the sealers dry some. Don't run the engine without coolant in it. Good luck.
Too bad that happened to the engine.
When you remove the head, clean it well, and check it with a straight edge, and see if the bottom of it is flat. If it is warped, it should be flattened at an engine shop.
Check the head and block for cracks. They can be small.
The people on here like to use Permatex Copper Spray on the new head gasket, before putting the head on the engine. It helps it seal well. Spray both sides of the gasket, just as you are going to put it together, and put the head on before the Copper Spray dries.
Use an even application of the spray on the gasket. Practice a little on some flat metal, if you have never used Copper Spray before. I think they sell it at NAPA.
When you put it together, the head bolts should have NON hardening sealer put on the bottom 1/2" of the threads before putting them in. The bolts go into the water jacket, and water can run up the bolt threads without sealer. tst has said this on here too, he rebuilds many Cub engines.
I use Permatex Aviation Form A Gasket, it is a non hardening liquid. It comes in a small can. They have it at NAPA here in the west US. If you buy one, stir it well, down to the bottom, before using it, it settles in the can sitting.
Before putting the head on, I would turn all the bolts in the holes by hand, without the sealer, and be sure they turn easily. Then remove them.
They have to turn easily to get an accurate torque reading. Use a tap in the holes to clean them, if needed, and a die on the bolts, if you didn't buy new bolts.
When it is together again, I would wait a day before putting coolant in the radiator and engine, it will let the sealers dry some. Don't run the engine without coolant in it. Good luck.
Attachments
I believe the problem occurred when I removed the head bolt that holds the spark plug wires to replace the part. It sits between #2 and 3. There is no water in oil so only leaked when bolt was out. Than the Cub did not run for 2 or 3 months which let the coolant do it's damage. Ran great before this event. What makes the valves go back down? If a valve will open but not close, will penetrating oil fix it?
Hi,
Each of the 8 valves has a spring that closes it. If the valve stem is too tight in the guide, from carbon build up, or rust, the valve won't close.
You can put penetrating oil on the valve stem upper ends when the head is off. Then tap gently on the valve head to move it down. Use a small wood block on the top of the valve, don't hammer directly on the valve.
They may need to soak with penetrating oil for some time, if they are tight.
Don't hammer hard on the valves.
The valve mechanism is behind the valve cover on the left side of the engine. That is where the springs are.
You will probably need to remove the cover, and spray penetrating oil on the lower ends of the valve stems, to help them move again.
The valve clearance is manually adjusted, and needs setting with a feeler gauge.
Below is a page from the Cub owner's manual showing how to adjust the valves. I would adjust them, after you get them working freely again.
http://farmallcub.com/rudi_cub/www.clea ... e%2039.jpg
Below is a pic from TM Tractor of the valve area on a Cub engine block. I don't have a pic of one with the parts in the block.
Each of the 8 valves has a spring that closes it. If the valve stem is too tight in the guide, from carbon build up, or rust, the valve won't close.
You can put penetrating oil on the valve stem upper ends when the head is off. Then tap gently on the valve head to move it down. Use a small wood block on the top of the valve, don't hammer directly on the valve.
They may need to soak with penetrating oil for some time, if they are tight.
Don't hammer hard on the valves.
The valve mechanism is behind the valve cover on the left side of the engine. That is where the springs are.
You will probably need to remove the cover, and spray penetrating oil on the lower ends of the valve stems, to help them move again.
The valve clearance is manually adjusted, and needs setting with a feeler gauge.
Below is a page from the Cub owner's manual showing how to adjust the valves. I would adjust them, after you get them working freely again.
http://farmallcub.com/rudi_cub/www.clea ... e%2039.jpg
Below is a pic from TM Tractor of the valve area on a Cub engine block. I don't have a pic of one with the parts in the block.
Attachments
Hi,
Good that the valves move again.
If the head is still off, you could put some light motor oil on the valve stems, under the valve heads, at the top of the stems, and turn the engine slowly, and try to work the oil down the stems some.
While the hood is off the engine, you could oil the fan hub, they use motor oil.
I would also clean the air cleaner, wash out the whole assembly, and clean the oil cup, and put in new motor oil in the cup.
Below are pages from the Cub owner's manual explaining how.
http://farmallcub.com/rudi_cub/www.clea ... age-28.jpg
http://farmallcub.com/rudi_cub/www.clea ... age-29.jpg
You should oil the fan hub even if you put the hood on, people on here have had them seize from no oil in them.
I use a pump oil can from the right side of the fan, be sure it is clean motor oil in the oil can.
When the air cleaner is off the engine, I put in solvent into the mesh area, with it upside down, put on the oil cup, with no oil in it, and slosh it around well, remove the oil cup, then pour it out.
If you pour it out into a clean oil drain pan, you can see what was in the air cleaner.
Repeat the sloshing with clean solvent until it looks clean. Hold it on it's side, and right side up, and slosh it also.
The solvent will probably run out the hole for the pipe to the carburetor when upside down with solvent in the air cleaner. Cover it first with some duct tape, or a plug of some kind, will help. Remove the tape, or plug, when done cleaning.
Clean out the pipe through the center of it also, like the manual says.
Usually the original style cap on top of the pipe is made so it will tighten if you hit it lightly, one hit, with a rubber hammer, when it is in position.
Without hitting it, the cap is sitting there loose.
Below is the 1949 Cub owner's manual, if you don't have it. The experts on here recommend reading it, it has lots of info about operation, maintenance, and lubrication. There is a table of contents on page 1.
It has pics of how the Cub was originally.
The recommendation for using motor oil in the Touch Control was changed later, to use Case IH Hy - Tran fluid, Jim Becker has said.
http://farmallcub.com/rudi_cub/www.clea ... index.html
Good that the valves move again.
If the head is still off, you could put some light motor oil on the valve stems, under the valve heads, at the top of the stems, and turn the engine slowly, and try to work the oil down the stems some.
While the hood is off the engine, you could oil the fan hub, they use motor oil.
I would also clean the air cleaner, wash out the whole assembly, and clean the oil cup, and put in new motor oil in the cup.
Below are pages from the Cub owner's manual explaining how.
http://farmallcub.com/rudi_cub/www.clea ... age-28.jpg
http://farmallcub.com/rudi_cub/www.clea ... age-29.jpg
You should oil the fan hub even if you put the hood on, people on here have had them seize from no oil in them.
I use a pump oil can from the right side of the fan, be sure it is clean motor oil in the oil can.
When the air cleaner is off the engine, I put in solvent into the mesh area, with it upside down, put on the oil cup, with no oil in it, and slosh it around well, remove the oil cup, then pour it out.
If you pour it out into a clean oil drain pan, you can see what was in the air cleaner.
Repeat the sloshing with clean solvent until it looks clean. Hold it on it's side, and right side up, and slosh it also.
The solvent will probably run out the hole for the pipe to the carburetor when upside down with solvent in the air cleaner. Cover it first with some duct tape, or a plug of some kind, will help. Remove the tape, or plug, when done cleaning.
Clean out the pipe through the center of it also, like the manual says.
Usually the original style cap on top of the pipe is made so it will tighten if you hit it lightly, one hit, with a rubber hammer, when it is in position.
Without hitting it, the cap is sitting there loose.
Below is the 1949 Cub owner's manual, if you don't have it. The experts on here recommend reading it, it has lots of info about operation, maintenance, and lubrication. There is a table of contents on page 1.
It has pics of how the Cub was originally.
The recommendation for using motor oil in the Touch Control was changed later, to use Case IH Hy - Tran fluid, Jim Becker has said.
http://farmallcub.com/rudi_cub/www.clea ... index.html
When ever I pull a head on any engine I get it cut .010” or to clean. This way when I reinstall the head I know it’s good. Don’t forget to retorque once it’s up to temp and cools off.
My moto is do it once, do it right. When skimping things can come back to bite us don’t ask me how I know.
My moto is do it once, do it right. When skimping things can come back to bite us don’t ask me how I know.