TO-30 Compression

[Jim in TN]

What is the probable cause of 40 psi in the #4 cylinder? The pressure didn't change even when oil was added. The other 3 cyclinders averaged 70-80 psi. In addition I fould that the starter nose cone was broken. Replace it or weld it? Any thoughts?

Enough adventure for one day!

 

[Jerry/MT]

You probably have a burned exhasut valve that"s causing that low of a compression. The minimum allowable compression is no less than 90 psi. This is for a an engine at operating temperature with the throttle plate wide open and no air cleaner restriction. You maybe looking at replacing the rings.

you can try brazing or welding the nnos cone.ake sure that there is a thrust washer on the shaft between the starter gear and the nose cone. Not having one is the useual cause of breakage.

 

[Branlin]

Adding oil seals the rings somewhat, so if they're bad the number will go up. If the number doesn't go up after adding oil, then it's likely the valves, as Jerry suggested.

Aside from a burned valve, also check for a sticky valve. I ignored mine too long and it ended up going through the piston. Oh well, it needed a rebuild anyway. The old piston with the valve driven through it makes a great conversation piece.

 

[Jim in TN]

Would the compression improve with the valves adjusted?

We have just purchased the tractor (the first ever owned by the family farm). In addition, my family has just completed our first year (ever) weekend farming. Talk about a steep learning curve!
We had borrowed a T030 to use this year and have been impressed by the simplicity and relability of the fergie tractors.

 

[gshadel]

Jim, low compression after adding oil to the cylinder is typically indicative of poor valve seal, or blown head gasket. Poor valve seal can be burned/worn valves, sticking valves, build-up, or a seriously out of adjust problem. The least effort, 1st check is to pull the gas tank, valve cover, and check/adjust the tappet clearance on valves for # 4, may as well check-em all while your there. Watch your valve motion thru a couple turns of the crank to make sure they are not sticking. If that does not improve your compression, your next step would be to pull the head to clean/inspect/replace your # 4 valves & possibly lap/polish the valve ports on the head if needed. You will need a new head gasket if you pull the head. With a service manual it is not a difficult job to do all that, the only "special tool" you would probably need is a valve spring compressor so you can safely remove your valve springs. You can often borrow those, or rent for free from your local auto parts chain store, or make something of your own with a bent screwdriver.
If you pull your head, a typical machine shop will charge you ~$70-80 to check your head for warp, clean, check for cracks, and grind/polish your valve ports, that is after you have stripped down the valves, springs, etc. off the head. Well worth the expense & piece of mind.

George