Compression problem

Sat Nov 05, 2011 6:53 am

I am new to the Cub site and have just gotten a 1956 Cub. It had not been running for about 2 years. I got it to start and it had a miss. The more I tried to fine tune it the worse it has gotten. I pulled the plugs and checked the compression 1 and 4 had about 90 lb. 2 and 3 10 to 0. Does this sound like a head gasket to you? I ordered the set and will be taking it apart next week if all goes well. It has no water in the cylinder or oil pan that I can see. Thanks for your help in advance. This is a great site for the NEW Cub owner :D
Last edited by ShineRunner on Sat Nov 05, 2011 8:58 am, edited 1 time in total.

Re: Compression problem

Sat Nov 05, 2011 7:03 am

Stuck valve

Re: Compression problem

Sat Nov 05, 2011 7:24 am

Test the compression again, do a wet test this time if it is still low, take off the valve cover and see if the valves are moving.
Go from there..........

Bruce T.

Re: Compression problem

Sat Nov 05, 2011 7:30 am

Agree with the others stuck valves.

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Re: Compression problem

Sat Nov 05, 2011 8:56 am

I will do the wet test and check the valves through the side plate before taking the head off. What is the best way to free up stuck valves? Having a great time working on this little red tractor. The engine sounds solid except for the miss. Thanks

Re: Compression problem

Sat Nov 05, 2011 9:17 am

ShineRunner wrote:What is the best way to free up stuck valves?
Use the search function at the top of the page. There are several recent discussions on freeing up stuck valves.

You may not need to remove the head. It all depends on how stuck the valve(s) are.

Re: Compression problem

Sat Nov 05, 2011 9:19 am

Stuck valves :!:

Why do I know this :?: Dealing with the exact same problem with my 47 - Granny - here is the thread - Stuck Valves. Pull the plugs on 2 and 3, pour in 1 tablespoon of oil, rotate engine by hand a couple times. Take the side valve cover off. Spray the valves/valve springs and tappets with your favourite penetrating oil. I like Nut Buster and Loctite's Solvo-Rust. Rotate the engine by hand with/without hand crank again but while watching the valves functioning. You should see whether it is exhaust or intake valves that are sticking. Take a standard screwdriver and very.. very gently tap the offending valves once or twice. I used a dead blow mallet to reduce the shock to the valves. Spray the valves in the spark plug holes with your favourite penetrating oil. Rotate the engine by hand a couple times hopefully twice each cycle. Continue to do this until the valves drop and drop they will. They are just stuck up because of carbon/oxidation.

After the valves have dropped, add another tablespoon of oil to each spark plug hole and hand crank the engine again. When you feel the valves are moving freely, add some SeaFoam to both the gas tank and the crankcase according to the directions on the label. This will help clean the valves/valve stems and guides. It may still take a bit to get the engine to fire up, but this is the first step.

Re: Compression problem

Sat Nov 05, 2011 9:28 am

Eugene wrote:
ShineRunner wrote:What is the best way to free up stuck valves?
Use the search function at the top of the page. There are several recent discussions on freeing up stuck valves.

You may not need to remove the head. It all depends on how stuck the valve(s) are.

I agree, but if you are like me and have a new head gasket available, I would be just curious enough to want to see what things look like under that head on your new Cub. It makes getting to the valves much easier and you can clean all that carbon out of there. But that's just me. :roll:

Congrats on the new '56. :-:-):

Re: Compression problem

Sat Nov 05, 2011 9:35 am

i hope you are not planning on hauling shine with that cub, not very fast. :bellylaugh: :bellylaugh: welcome to the site. tomcat

Re: Compression problem

Sat Nov 05, 2011 10:01 am

tomcat wrote:i hope you are not planning on hauling shine with that cub, not very fast. :bellylaugh: :bellylaugh: welcome to the site. tomcat


Not a problem, The revenooers would NEVER suspect a slow vehicle! Ed

Re: Compression problem

Sat Nov 05, 2011 1:33 pm

I live only a few miles N of Junior Johnson in Wilkes County NC. I am in the Real Estate business now and Charlie Felts Jr. is one of the guys that I deal with now in the real estate business. His dad was one of the main revenuers (with the same name) when the product was in demand.

Re: Compression problem

Sat Nov 05, 2011 8:42 pm

I have been to Jr.s old shop. I think Flossie still lives there
Boss

Re: Compression problem

Sat Nov 05, 2011 8:44 pm

Have also been by his small :D new house
Boss

Re: Compression problem

Sat Nov 05, 2011 8:44 pm

Must take a small army to tend to the grounds there

Re: Compression problem

Sat Nov 05, 2011 10:34 pm

I agree with Rudi's instructions. I freed the valves (2) using this method on a 1952 Cub engine that had sat more than 30 years without being rotated. It took about 2 weeks of random tries, plenty of patience and penetrating lubricant. I like PB Blaster and ATF. (Using a wooden hardwood dowel instead of a screwdriver might keep from niching the metal.) Stan

EDIT NOTE: I was able to lubricate and tap the top of the valves through the spark plug hole after removing the hood.
Last edited by staninlowerAL on Sun Nov 06, 2011 8:55 am, edited 1 time in total.