8N cylinder 1 low compression

fpappal

Member
I have an 8N that last fall started running rough at high idle. It got to the point that I could not use the finish mower with it because it would
start to cut out with the engine revved up. It idled just fine however. Today I decided to take a closer look. I have 35 psi compression in
cylinder 1 and 90 in the other three. I squirted some oil in cylinder one and the compression jumped up to about 70 psi. I am calling cylinder 1
the cylinder closest to the steering wheel. The engine was rebuilt by a previous owner but I do not know the details of the rebuild.

It was suggested to me that possibly the sleeve has moved just a bit and some seal has moved as a result? Does that even make sense? I have
rebuilt a few Deere's but never did anything major with a Ford. The distributor is mounted in the front if that is of any help. I do have a
service manual but it is not at my house right now so I will have to wait to take a look at it.

Any chance this could simply be a head gasket? Is my next step removing the head? Any help would be appreciated.
 
That would be cylinder 4, but yank the head and take a look, drop one sleeve and piston in if needed and be on your way. Could be valves, head gasket but usually would see it leaking to outside, but easy enough to look on a flathead
 
(quoted from post at 19:42:52 06/12/16) I have an 8N that last fall started running rough at high idle. It got to the point that I could not use the finish mower with it because it would
start to cut out with the engine revved up. It idled just fine however. Today I decided to take a closer look. I have 35 psi compression in
cylinder 1 and 90 in the other three. I squirted some oil in cylinder one and the compression jumped up to about 70 psi. I am calling cylinder 1
the cylinder closest to the steering wheel. The engine was rebuilt by a previous owner but I do not know the details of the rebuild.

It was suggested to me that possibly the sleeve has moved just a bit and some seal has moved as a result? Does that even make sense? I have
rebuilt a few Deere's but never did anything major with a Ford. The distributor is mounted in the front if that is of any help. I do have a
service manual but it is not at my house right now so I will have to wait to take a look at it.

Any chance this could simply be a head gasket? Is my next step removing the head? Any help would be appreciated.
b:8197164d23][i:8197164d23]

#1 cyl. is up by the radiator!


If the cyl. you poured oil into, 'jumped up in pressure',.....I suspect you are having stuck valves, and/or rings problems.
Before you go ripping the head off, pour some ATF into each cyl., and let it set for at least 24hrs.,.....then do another comp. reading with engine warmed up.
If the comp. comes up.......then run the P-wadden out of it for a couple of days....see if the engine gets healthier!!???
:lol:

Gary[/i:8197164d23][/b:8197164d23]
 
HOBO, You talk like one of those instructors at CAMDEN, SC Military Academy.

Keep up the good work.


John,PA
 
If a valve was stuck why would the oil I added increase the compression? Something must be going on with they cylinder itself whether it is a ring or the sleeve. I realize there are quite a few unknowns so I will have to spend a few hours with it. Can the head be removed without taking the hood and tank off? What are the chances I can reuse the head gasket? Thanks for all the replies.
 
(quoted from post at 06:00:39 06/13/16) If a valve was stuck why would the oil I added increase the compression? Something must be going on with they cylinder itself whether it is a ring or the sleeve. I realize there are quite a few unknowns so I will have to spend a few hours with it. Can the head be removed without taking the hood and tank off? What are the chances I can reuse the head gasket? Thanks for all the replies.

During compression testing, the oil that you put in the cylinder gets blown around inside the combustion chamber. During this time, the valves are also opening and closing. Some of that oil can get blasted onto the valve stems and seep down the stems. The action of "power lubricating" the valves with compressed oil vapor and working the valves by the cam/tappets during the compression test can sometimes free a sticky valve.
 

If you're in the mood to tear something apart, my humble opinion is to try taking off the intake/exhaust manifold and valve covers. The risks there are:

A: You may need a new manifold gasket, which is relatively cheap.

B: You may have some fun with your manifold mounting bolts. Mine looked like unrecognizable hunks of rust, but they came off surprisingly easy after an application of automatic transmission fluid applied with a needle and syringe, waiting aout an hour and a quick touch of heat from a MAPP gas soldering torch. (I hate spray lubricants.)

That way, you can lubricate and loosen the valves without putting a bunch of crap in your cylinders.
 
Before you tear it apart do a compression test with the spark plug in in the adjoining cylinder, then with it out.If it changes most likely a head gasket, yes oil would help seal a fracture in the gasket.
 
It works!! I went out to check the compression again today and it was at 90 psi. Must be the oil sitting in it over night freed up the stuck valve.

Now I am back to the problem I had with it last fall when I put it away. The tractor purrs like a kitten but only if it is on half choke. As I increase the throttle I also need to pull the choke lever out slightly as well. It seems to me like it is not getting enough fuel. The two adjustment screws appear to not do a thing. I can screw them all the way in or back them off and nothing changes. I have plenty of fuel getting to the carb from the tank. The current carb is a MS but the it had a Zenith on it when I got the tractor. I could not get the float to keep from leaking on the Zenith so I found an original MS carb in a junk yard. I am going to put the zenith back on to see if there is any difference.

What else besides lack of fuel would require the tractor to run at half choke?
 
" What else besides lack of fuel would require the tractor to run at half choke? "

A lot of things.

Pulling out the choke gives you a richer mixture. So, you could have either a fuel or spark problem.

A carb out of adjustment will also cause this problem; set the main jet at 1-1/2 turns out & leave it alone.

A dirty carb can cause the problem as well; start by cleaning the fuel screens.

Dirty/old gas, or water in the gas can cause this problem.

Restricted fuel flow can cause this problem; remove the bolt at the bottom of the carb & check for flow.

On my 1950 frontmount, needing choke to run is the first sign that the points need adjusting/replacing.

A vacuum leak can do the same thing. Get a hand propane torch and carefully spray it (unlit of course) around the intake manifold at the carb to manifold interface & the manifold to block gasket of the tractor while it is running. Or, you can use carb cleaner or WD40. If it speeds up, you found the leak. Sometimes (rarely) manifolds crack or get rust holes.

Lastly, when all else fails, you could have an air leak around the carb metering section. The likely suspects are leaky throttle shaft seals and/or a worn throttle shaft. Or, just a real dirty carb w/ clogged passages.

Bottom line: Probably 90% of "needs choke to run" problems are fuel related, but do not rule out ignition problems, contrary to what others may tell you. I?ve had that very same problem before w/ a rebuilt carb, fresh fuel & good flow & a tight manifold.......and it was a spark problem. But, that was unusual. Just check the likely fuel problems first.
75 Tips
 
[b:3a6ae5f5bb][i:3a6ae5f5bb]

" Must be the oil sitting in it over night freed up the stuck valve."

YEP.....thats why I told ya to do it with oil, in the bores.!!!

As for the carb needing choke to run properly, Sounds to me like the carb has a plugged up passage somewhere, and needs to be cleaned out.

Here is a picture to show the passages to run wire and air through, to help clean it out.


If that does not do the trick......post back for more help!!!

Gary
[/i:3a6ae5f5bb][/b:3a6ae5f5bb]
 
Turns out the problem was with the carb. When I got the tractor it had an aftermarket carb on it. I cleaned up that carb, put it on the tractor and it started right up. No longer needs half choke. Must be the MS carb I bought has a clogged passage somewhere. Either way now that it is running I plan on putting it on the side of the road with a for sale sign on it.
 
(quoted from post at 06:44:06 06/16/16) Turns out the problem was with the carb. When I got the tractor it had an aftermarket carb on it. I cleaned up that carb, put it on the tractor and it started right up. No longer needs half choke. Must be the MS carb I bought has a clogged passage somewhere. Either way now that it is running I plan on putting it on the side of the road with a for sale sign on it.
b:f244a36aee][i:f244a36aee]

Thanks for the update! Glad you got it up and running!!
Don't throw the unused MS carb away. It can still be cleaned up, and useful for many yrs, to the right person!!!

Gary :wink: [/i:f244a36aee][/b:f244a36aee]
 
I am half tempted to put the MS carb on and see how it runs. When I was cleaning it out I blew some air in one of the passages
and something came out and hit me in the face!! I am curios to see if that was the problem or if there is still some blockage
somewhere. Either way I will def not throw it away.
 
(quoted from post at 10:21:45 06/16/16) I am half tempted to put the MS carb on and see how it runs. When I was cleaning it out I blew some air in one of the passages
and something came out and hit me in the face!! I am curios to see if that was the problem or if there is still some blockage
somewhere. Either way I will def not throw it away.
b:ec8ad65348][i:ec8ad65348]

Don't let the temptation go only half-way. You can't lose by trying it out, and even if it won't run so good, at first, tear it down and give it a good cleaning for another try at running.

Either way you go......keep us up-dated!!!

Gary[/i:ec8ad65348][/b:ec8ad65348]
 

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