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Have no compression

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Command52
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Have no compression

Postby Command52 » Sat Dec 30, 2017 12:49 pm

I have the 1950 cub ,I have never had it running myself but I know it was setting for at least 5 years , It has a magneto so I was trying to put it on top dead center to time magneto, I took out #1 plug but I have no compression, I took out the rest of the plugs and I have 25lbs #2 22lbs #4 27lbs #3 And nothing registering on a manual dial gauge On #1 What to you think stuck rings? If it is and I could get it timed would it start on this low compression to try loosen rings up if that is what it is, Also not having compression in #1 is there another way to know when its on top dead center to time magneto Thank you ahead for your great help

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Eugene
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Re: Have no compression

Postby Eugene » Sat Dec 30, 2017 12:56 pm

The #4 cylinder is on the same crankshaft throw as the #1 cylinder. If you can get compression on the #4 cylinder and the pointer/pulley mark line up - - then 360 degree rotation of the crankshaft back to the pointer/pulley mark line up - - - you are at TDC #1 cylinder.

The engine will not start with that low of compression. Free up the #1 cylinder's valves and top soak the pistons with solvent. If you can get the dry compression up into the 70 psi range, engine will start.
I have an excuse. CRS.

Command52
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Re: Have no compression

Postby Command52 » Sat Dec 30, 2017 1:02 pm

Can I reuse the old head gasket until I know I have the problem fix

Eugene
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Re: Have no compression

Postby Eugene » Sat Dec 30, 2017 1:16 pm

Command52 wrote:Can I reuse the old head gasket until I know I have the problem fix
I wouldn't remove the head until I made sure all the valves were functioning and had soaked the top of the pistons in solvent for a while.

Don't get impatient. Run through the prepeations to get the engine running. Then run the engine for several hours. Again check the compression, dry then wet.

My guess is that the engine is due for a complete overhaul.

Can you reuse a used head gasket just to start up an engine? Perhaps, depends on the condition of the gasket, but I wouldn't do it. Idea is to make sure you are not doing a step/procedure, or spending the money, more than once.
I have an excuse. CRS.

BigBill
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Re: Have no compression

Postby BigBill » Sat Dec 30, 2017 1:22 pm

Add seafoam to the crankcase and fuel tank and run it. The rings and valves are dry. Seafoam will loosen stuck rings and free the sticky valves.
I'm technically misunderstood at times i guess its been this way my whole life so why should it change now.

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John *.?-!.* cub owner
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Re: Have no compression

Postby John *.?-!.* cub owner » Sat Dec 30, 2017 3:08 pm

Try squirting some oil in each cylinder. Note, the spark plugs are over the valves so you need to point the squirt can towards the center to get oil on top of piston, then turn it over a few times by hand and check compression again. Remember compression check needs to be done by starter, not by hand, with throttle full open, and all spark plugs removed for most accurate results. The compression numbers you saw are normal for an engine that has set several years. Oil runs down off cylinder walls and out of ring grooves over time and without that oil there is practically no compression.
If you are not part of the solution,
you are part of the problem!!!

Eugene
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Re: Have no compression

Postby Eugene » Sat Dec 30, 2017 3:57 pm

Prime the oil pump if you haven't done so -FIRST THING.

If you are hand cranking the engine during compression tests, the numbers will be very low.
I have an excuse. CRS.

Command52
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Re: Have no compression

Postby Command52 » Sat Dec 30, 2017 5:13 pm

Thanks again for all this great information, I did have a stuck valve on #1 and I will follow all this information Thanks

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Mike in Louisiana
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Re: Have no compression

Postby Mike in Louisiana » Sat Dec 30, 2017 6:04 pm

Why do you think it is out of time????
1975 cub (LouAnn) serial # 245946, 1941 John Deere Model H

Good judgment comes from experience,
and a lot of that comes from bad judgment. Will Rogers

Command52
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Re: Have no compression

Postby Command52 » Sat Dec 30, 2017 6:16 pm

I had to pull the magneto to get to the screws on the distributor cap , Its a weird magneto set up

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Glen
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Re: Have no compression

Postby Glen » Sat Dec 30, 2017 8:47 pm

Hi,
You usually don't have to remove the head to loosen stuck valves. Remove the valve cover, behind the carburetor, and you can get to the bottom end of the valves, and lube the lower end of the valve stems.
If you have the cover off, it is a good time to adjust the valve clearance. They have to be adjusted manually, with a feeler gauge.
Some of the guys on here have said that their engines work better with the valves set right.
Below is a page from the 1950 Cub owner's manual showing how to adjust the valves.

http://farmallcub.com/rudi_cub/www.clea ... e%2039.jpg

Below is the whole 1950 Cub owner's manual. The experts on here say people should read the owner's manual. It has lots of info about operation, maintenance, and lubrication. There is a table of contents on page 1. :)

http://farmallcub.com/rudi_cub/www.clea ... index.html

inairam
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1949 with kub klipper belly mower. mag 6v - Mom
1950 with plow, 54 blade, mott mag 6v - Roxanne
1953 54 blade, c22, wood 42 6v
1957 6v - barn Queen
1965 lo-boy with c-3 mower 12 v - Loboy
1974 Horse II 12 v c-2
1975 with woods 42-6 12 v - Horse
1979 long strip 12 v stuck engine
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Re: Have no compression

Postby inairam » Sun Dec 31, 2017 8:44 am

Also from what I have read on the formun and my experience 0.015 is the general consensus vs the .013 clearance in the manual. I did an adjustment per the manual and still had some compression issues and members said to go to 0.015

I do not remember who wrote this but a member wrote something to the effect " there is not a cub out there that would not benefit from a valve adjustment or a valve job."
When you only have 9 horsepower you need to know the names of all of the ponies!


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