This site uses cookies to maintain login information on FarmallCub.Com. Click the X in the banner upper right corner to close this notice. For more information on our privacy policy, visit this link:
Privacy Policy

NEW REGISTERED MEMBERS: Be sure to check your SPAM/JUNK folders for the activation email.

Low compression and valves

The Cub Club -- Questions and answers to all of your Cub related issues.
Forum rules
Notice: For sale and wanted posts are not allowed in this forum. Please use our free classifieds or one of our site sponsors for your tractor and parts needs.
User avatar
Ronny Bailey
10+ Years
10+ Years
Posts: 719
Joined: Thu Oct 23, 2008 2:38 pm
Zip Code: 77802
eBay ID: ronnyb.east.texas
Tractors Owned: 1938 Farmall F-20
Grandpa's '49 Cub #82289
194x Gibson Model D
1953 Allis Chalmers CA
Location: TX, Bryan

Low compression and valves

Postby Ronny Bailey » Wed Mar 18, 2009 3:16 am

Reading Larry's post, I noticed a lot of folks think his low compression (40#) is probably related to the valves.
I understand that if they don't seal, you can't get good compression.

If this is a valve problem:
The fact that all four cylinders have the low readings must mean that each has at least one valve with a bad seal.
Is this unusual? It seems to me the likelihood that all four would have valve problems would be kind of remote.
I read that the engine hasn't run for about 20 years and some valves were stuck.

I was just curious about this and thought I'd ask.
After the valves on mine were loose, I chipped away a lot of carbon off the valves and seats.
Used an old vacuum cleaner while doing it so nothing would fall into the engine.
Haven't done a vacuum test on it, but it sounded good at the LA Cubfest when it was running.
Ronny
“If it ain’t broke, I haven’t 'fixed' it yet”

SPONSOR AD

Sponsor



Sponsor
 

DanR
10+ Years
10+ Years
Posts: 1631
Joined: Fri Dec 22, 2006 6:28 am
Zip Code: 37743
Circle of Safety: Y
Location: Tennessee East

Re: Low compression and valves

Postby DanR » Wed Mar 18, 2009 5:20 am

Ronny you are right about a 'bad seal' on each valve. I would rather think it is a carbon problem. Carbon is not selective. It can cause valves to stick or nor seat and hold rings tight. Just put a pint or so of kerosene in the oil and run it under load for a few hours. You will be surprised how much dissolved carbon will drain out . You can do this until the oil looks more like oil and not hurt anything.
47 Cub (Glenda)
52 Super A
62 Cub (Genie)
43 H
42 M
In all things know which way the wind is blowing.

User avatar
Lurker Carl
Cub Pro
Cub Pro
Posts: 3970
Joined: Mon Feb 03, 2003 9:54 am
Zip Code: 16685
Circle of Safety: Y
Location: PA, Todd

Re: Low compression and valves

Postby Lurker Carl » Wed Mar 18, 2009 6:35 am

A rich fuel mixture left unchecked over years of operation, as will worn rings, will create the carbon deposits on the exhaust valves that result in poor compression. So will disregarding regular maintanence. A too hot combustion temperature will erode the valves and seats. Worn valve guides can cause the valves to rest off center on the seat. Rust could be a culprit with an unused engine.

I'm not a big fan of diluting the crankcase oil with any solvents that are meant to "clean out" particles within the engine. The Cub engine can not efficiently remove these particles from the oil because only part of the oil flowing from the pump is routed through the filter. The rest of the crud-laden oil makes it's way to the various bearings throughout the engine. Engine deposits are best left alone or physically removed when the parts are dismantled.
"Chance favors the prepared mind."
- Louis Pasteur

"In character, in manners, in style, in all things, the supreme excellence is simplicity."
- Henry Wadsworth Longfellow

Former Member
10+ Years
10+ Years

Re: Low compression and valves

Postby Former Member » Wed Mar 18, 2009 9:19 am

For cleaning up the carbon without adding solvent to the oil or anything mechanical, My Dad and I like to do this process when we get a new, used motor.

We use Lucas fuel treatment. Use your favorite brand.

With the engine running at high idle, slowly squirt the lucas directly into the throat of the carb. It will start to load up and blow white smoke and probably spit some carbon out the exhaust. Stop squirting before it dies and let it clear out.


Do it again. The third time, squirt enough in the kill it. Choke it right down till it dies. Turn it off and let it sit overnight, so that it has time to desolve what is left of the carbon in the cylinder, rings, and both intake and exhaust valves.

When you restart it, it will smoke the white smoke, but will clear up and should hep your compression problem.

User avatar
Lurker Carl
Cub Pro
Cub Pro
Posts: 3970
Joined: Mon Feb 03, 2003 9:54 am
Zip Code: 16685
Circle of Safety: Y
Location: PA, Todd

Re: Low compression and valves

Postby Lurker Carl » Wed Mar 18, 2009 10:13 am

dshawz wrote:Do it again. The third time, squirt enough in the kill it. Choke it right down till it dies.


Be very careful when adding liquids into the air intake of any engine, it can create a hydraulic lock up. It's a proven method for instantly destroying an engine.

Image
"Chance favors the prepared mind."
- Louis Pasteur

"In character, in manners, in style, in all things, the supreme excellence is simplicity."
- Henry Wadsworth Longfellow

User avatar
ToddW
Cub Pro
Cub Pro
Posts: 2293
Joined: Tue Sep 02, 2008 3:46 pm
Zip Code: 54911
Tractors Owned: -
1951 F-Cub
1960 Yellow Loboy
Despeeder, FH Rototiller, / FH York Rake, FH plow, 152 Disk plow, Woods brush mower, Wagner Loader, Grader Blades, 23-A Disc Harrow. Spike tooth harrow
FORD JUBILEE with Sherman 12-speed
1953 Ford F-100 Jubilee
Cadet 108 with mower and snow thrower -Cadet 1650 with deck and thrower
Circle of Safety: Y

Re: Low compression and valves

Postby ToddW » Wed Mar 18, 2009 10:31 am

I've read posts here in the forum about running the engine briefly with 1/2 pint kerosene added to motor oil to clean the crud out. Wouldn't this be a good idea to try to improve compression and remove deposits
Last edited by ToddW on Sun Mar 22, 2009 9:28 am, edited 1 time in total.

DanR
10+ Years
10+ Years
Posts: 1631
Joined: Fri Dec 22, 2006 6:28 am
Zip Code: 37743
Circle of Safety: Y
Location: Tennessee East

Re: Low compression and valves

Postby DanR » Wed Mar 18, 2009 10:37 am

Don't run the engine with kerosene only! A pint or so with the oil will do the trick. A few minutes will not work either. A few hours is needed for the kerosene to do it's work.
47 Cub (Glenda)
52 Super A
62 Cub (Genie)
43 H
42 M
In all things know which way the wind is blowing.

User avatar
ricky racer
10+ Years
10+ Years
Posts: 6303
Joined: Wed Sep 12, 2007 8:40 pm
Zip Code: 49120
Circle of Safety: Y
Location: Niles / Buchanan, Michigan

Re: Low compression and valves

Postby ricky racer » Wed Mar 18, 2009 11:17 am

A simple way to see where compression is lost is to induce compressed air to each cylinder and see where it leaks from. You can use the threaded end of a compression tester on many brands or make an adapater from an old spark plug that you can attach an air hose to and induce regulated compressed air into each cylinder to see where it's leaking. If you hear air coming out the exhaust, it's leaking past the exhaust valve. If you hear it leaking out the carb, it's leaking past the intake valve. If you hear it leaking out the crank case filler pipe, it's leaking past the rings. Once you know where it's leaking, you'll know what you have to do to "Get-R-Done"!
:big afro:
1929 Farmall Regular
1935 John Deere B
1937 John Deere A
1941 John Deere H
1952 John Deere B
1953 Farmall Cub

Eugene
Team Cub Mentor
Team Cub Mentor
Posts: 20336
Joined: Fri Jul 02, 2004 9:52 pm
Zip Code: 65051
Circle of Safety: Y
Location: Mo. Linn

Re: Low compression and valves

Postby Eugene » Wed Mar 18, 2009 7:25 pm

I noticed a lot of folks think his low compression (40#) is probably related to the valves. I understand that if they don't seal, you can't get good compression.

The fact that all four cylinders have the low readings must mean that each has at least one valve with a bad seal. Is this unusual? It seems to me the likelihood that all four would have valve problems would be kind of remote. I read that the engine hasn't run for about 20 years and some valves were stuck.
On one cylinder both valves are open for about 15 degrees of crankshaft rotation. Depending on where a 4 cylinder engine stops in the combustion cycle it is possible to have a valve open in at least 3 if not all 4 cylinders. An engine sitting for 20 year - gonna have problems.

More than likely had problems before it was parked.

Grammer correction.
Last edited by Eugene on Wed Mar 18, 2009 8:28 pm, edited 1 time in total.
I have an excuse. CRS.

User avatar
ricky racer
10+ Years
10+ Years
Posts: 6303
Joined: Wed Sep 12, 2007 8:40 pm
Zip Code: 49120
Circle of Safety: Y
Location: Niles / Buchanan, Michigan

Re: Low compression and valves

Postby ricky racer » Wed Mar 18, 2009 7:42 pm

Eugene brings up a good point. In my earlier post I should have stated that each cylinder needs to be checked on it's compression stroke.
:brainfart:
1929 Farmall Regular
1935 John Deere B
1937 John Deere A
1941 John Deere H
1952 John Deere B
1953 Farmall Cub

User avatar
Ronny Bailey
10+ Years
10+ Years
Posts: 719
Joined: Thu Oct 23, 2008 2:38 pm
Zip Code: 77802
eBay ID: ronnyb.east.texas
Tractors Owned: 1938 Farmall F-20
Grandpa's '49 Cub #82289
194x Gibson Model D
1953 Allis Chalmers CA
Location: TX, Bryan

Re: Low compression and valves

Postby Ronny Bailey » Wed Mar 18, 2009 9:51 pm

Good info! Here's another question:
I've noticed that it's usually recommended that you remove all the spark plugs when using a compression checker.
Why is that?
Ronny
“If it ain’t broke, I haven’t 'fixed' it yet”

Eugene
Team Cub Mentor
Team Cub Mentor
Posts: 20336
Joined: Fri Jul 02, 2004 9:52 pm
Zip Code: 65051
Circle of Safety: Y
Location: Mo. Linn

Re: Low compression and valves

Postby Eugene » Wed Mar 18, 2009 10:12 pm

Ronny Bailey wrote:Here's another question: I've noticed that it's usually recommended that you remove all the spark plugs when using a compression checker. Why is that?
Example. On a 4 cylinder engine, the 3 cylinders not being tested will compress the air/fuel in the cylinder - slowing the number of rpms the engine is being cranked over by the starter. This may or may not effect the reading on the cylinder being tested. High compression engines, this will definitely make a difference. C-60 engine - not so much.

Actually, I done the compression test both ways. I'm looking more for even readings, in the satisfactory range. On a well worn engine it won't make any difference in the readings.
I have an excuse. CRS.

Gary Orr
10+ Years
10+ Years
Posts: 318
Joined: Mon Feb 25, 2008 8:16 pm
Zip Code: 44483
Circle of Safety: Y
Location: OH

Re: Low compression and valves

Postby Gary Orr » Wed Mar 18, 2009 10:34 pm

I have to agree with Lurker you don`t have a full flow oil filter & all that sludge will go through the bearings. Plus you can bend a rod if you put a licquid in the combustion chamber.

User avatar
Corky's Cub
10+ Years
10+ Years
Posts: 2453
Joined: Thu Mar 08, 2007 12:57 pm
Zip Code: 30607
Tractors Owned: Just One:
1957 Farmall Cub
"Corky"s Cub"
Location: Georgia, Jackson County

Re: Low compression and valves

Postby Corky's Cub » Wed Mar 18, 2009 11:30 pm

Eugene wrote:
Ronny Bailey wrote:Here's another question: I've noticed that it's usually recommended that you remove all the spark plugs when using a compression checker. Why is that?
Example. On a 4 cylinder engine, the 3 cylinders not being tested will compress the air/fuel in the cylinder - slowing the number of rpms the engine is being cranked over by the starter. This may or may not effect the reading on the cylinder being tested. High compression engines, this will definitely make a difference. C-60 engine - not so much.

Actually, I done the compression test both ways. I'm looking more for even readings, in the satisfactory range. On a well worn engine it won't make any difference in the readings.


Eugene's got it...and there's another problem that might not be so pronounced on the cub...on bigger engines, if you constantly run un-burned fuel through the engine by turning it over, it can cause premature wear on the valve guides and rings and make the engine run smoky way before it's time.

Corky
I found this old Cub, Forgotten and Forlorn,
With pistons and valves frozen and worn.
Help from my buddies on Farmallcub.com,
And an engine from Ralph, (37’s the one),
Now ole Corky is running and back to life,
Much to the surprise of my dear, dear wife!

User avatar
Winfield Dave
10+ Years
10+ Years
Posts: 3555
Joined: Thu Apr 22, 2010 2:31 pm
Zip Code: 17953
Tractors Owned: ......Almost enough.
N3NIK
Circle of Safety: Y
Location: PA, Middleport (Schuylkill County)

Re: Low compression and valves

Postby Winfield Dave » Thu Sep 09, 2010 6:09 am

Earlier this week I was reading some posts here about using a vacuum gauge to help diagnose engine issues.
Maybe this would be of some help?...It seemed to identify different problems by the gauge reactions.
I haven't done it....just sharing.
Dave
"More gold has been mined from the thoughts of men than has been taken from the earth." -- Napoleon Hill


Return to “Farmall Cub”

Who is online

Users browsing this forum: Garvin Gatewood and 21 guests