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'51 Cub Power Issues

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AgTires4295
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Zip Code: 20646
Tractors Owned: 1940 Farmall A
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1964 Simplicity Landlord
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Location: La Plata, MD

'51 Cub Power Issues

Postby AgTires4295 » Wed Apr 15, 2015 6:38 pm

Hey Cub Family, Im having some power issues with my 1951 Cub. It started mid-summer last year and it's been consistent ever since. Between moving 4 times, having another baby, being transferred at work and other life happenings, Ive never gotten around to completely fixing the issue and am currently pressed for time just to work on it at all.

Last summer, I was cutting a field and it kept bogging down and cutting out. It sounded like it was running on just 2 or 3 cylinders... kinda choppy sounding. I had a heck of a time everytime attempting to restart. I eventually had to winch it onto my trailer and haul it home. I then went on to eventually working on the carb. I completely cleaned, rebuilt, cleaned and cleaned it again. Same issues everytime. Lack of power and hard starts. I did a compression test and if I remember correctly, they were all around 110 with the #4 cylinder being a little lower.

Fast-forwarding to recently, I blew the clutch and had to have another put in by a shop (again, I just dont have time to break it in half and blindly figure out how to replace a clutch). While it was in the shop, I had the mechanic go all through the carb, trying to find the issue. He turned up nothing.

I have my Cub back now, working again on just 2 or 3 cylinders. I have a strong spark from the coil and zapped myself a few times making sure all plugs were seing that heavy blue spark and they were. It's sluggish to start cold but does and rumbles to life (very choppy with black smoke) and levels out after a few seconds.

In putting it in drive, 1st gear is fine. From a stop, second is okay but getting a little down on power. 3rd gear is where the trouble is. I have to feather the clutch and it studders or chops until it reaches a decent speed. If I start going up hill, it boggs down.

Im able to engage the PTO and cut grass but anything taller than 6" and it really struggles to the point of almost dying.

If I turn the tractor off after getting it up to operating temp (or it dies from too much of a load), it wants to start and almost does but never will. It chugs, puffs and coughs but never runs.

6v system, fresh fuel, great spark, clean and rebuilt carb and excellent timing.

Beyond that, Im stumped. Im sure I'll think of more symptoms later.
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tmays
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Re: '51 Cub Power Issues

Postby tmays » Wed Apr 15, 2015 6:53 pm

Excellent timing: have you checked to be sure you have the firing order correct?
Thomas

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tnestell
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Re: '51 Cub Power Issues

Postby tnestell » Wed Apr 15, 2015 7:40 pm

Check valve lash 0.015 cold?

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AgTires4295
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Re: '51 Cub Power Issues

Postby AgTires4295 » Wed Apr 15, 2015 8:08 pm

Ive timed that cub twice so I know it's perfect. The order is burned in my brain and on the valve cover (1-3-4-2).

I'm not sure about valve lash or even what that is. I'll be Google-ing that.
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tst
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Re: '51 Cub Power Issues

Postby tst » Wed Apr 15, 2015 8:09 pm

Good Compression check first, if good it has to be fuel or spark, check for good fuel flow, coils can break down after getting hot, points/condenser condition, point gap, no cracks in distributor cap?

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Rick Spivey
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Re: '51 Cub Power Issues

Postby Rick Spivey » Wed Apr 15, 2015 9:17 pm

Magneto or battery ignition? To me, sounds like ignition breaking down, even though you say it has a good spark. Is the point gap correct (0.020" for battery ignition, 0.013" for magneto)?
Rick Spivey
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AgTires4295
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Re: '51 Cub Power Issues

Postby AgTires4295 » Wed Apr 15, 2015 9:34 pm

tst wrote:Good Compression check first, if good it has to be fuel or spark, check for good fuel flow, coils can break down after getting hot, points/condenser condition, point gap, no cracks in distributor cap?


Yeah I did a compression test sometime in the fall with all showing around (if I remember correctly) around 110 except #4 which was just slightly less. It definitely has good fuel flow. If anything, too much. I forgot to mention that it floods out very easily and dribbles through the rebuilt carb. I've checked the float and needle to make sure nothing was sticking but I'm sure the gas flowing as much as it is isn't healthy for it (and my yard...). This would also explain why it puffs black smoke on a cold start and whenever I put a load on it (whether driving up a small grade or turning on the PTO). The black smoke and sputters only last for a few seconds and it clears up.

I'm wondering if I had done damage last year when I used a 12v jump pack to jump the starter (it's all I had in my truck in the field and I was in the middle of NOWHERE cutting grass) when it would stall out.

I'm not sure if the coil is original or not but it's the same one that's been on the tractor for the years that I've owned it. Even after running for an extended period of time, it shoots a heavy blue spark to the distributor.

The points/condenser are new as of 2012/2013 when I re-timed it last. Point gap is to standard that I remember but would be worth another check just for good measure although I can't imagine it would change since I put new points in.

I purchased a new distributor cap in the fall, hoping it may have been the problem since I had been filing the original to clean the contacts.
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1940 Farmall A
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AgTires4295
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Tractors Owned: 1940 Farmall A
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1970 Simplicity Broadmoor 728 (x2)
1984 Cub Cadet 782
1964 Simplicity Landlord
2014 Simplicity Broadmoor 23/50
Location: La Plata, MD

Re: '51 Cub Power Issues

Postby AgTires4295 » Wed Apr 15, 2015 9:37 pm

Rick Spivey wrote:Magneto or battery ignition? To me, sounds like ignition breaking down, even though you say it has a good spark. Is the point gap correct (0.020" for battery ignition, 0.013" for magneto)?


This is a battery ignition (I wish it was a magneto). I'm 99% sure the gap is correct and wouldn't think it would move since I was in there last but stranger things have happened.
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Re: '51 Cub Power Issues

Postby robertst » Mon Apr 20, 2015 9:49 am

I would change points and condenser,sounds like condenser is weak to me.

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AgTires4295
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Re: '51 Cub Power Issues

Postby AgTires4295 » Wed Apr 22, 2015 5:02 pm

Well I finally worked the Cub back into my schedule. Glen had PM'd me about a week ago suggesting the same as robertst. I switched the condenser with an old one I had laying around, lightly sanded and regapped the points, changed the oil, charged the 6v battery up and BOOM it fired right up without any hesitation. I even used some seafoam in the gas and squirted about 1/3 of the aerosol can of Seafoam into the carb intake (this leads me to the next question).

I had let the Cub warm properly for a good while at a low idle and gradually set the throttle to wide open. I then squirted the Seafoam and at one point, the engine started to knock! This scared the heck out of me so I immediately backed off. What was making that horrible knock??? Was that the engine beginning to hydrolock from the Seafoam spray??

I let it idle down, shut it off and let it sit awhile. I fired it back up and it smoked like crazy (expected) but ran amazingly. I even took it out to cut a two-acre field that easily had grown over two feet and it surprised the heck out of me with the restored power. I contribute the power restoration to everything but the Seafoam but figured it couldn't hurt.

Is there a chance I may have damaged something from those few seconds of loud knocking???
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Re: '51 Cub Power Issues

Postby staninlowerAL » Wed Apr 22, 2015 6:04 pm

I had a similar experience with a GM 350 cu. in. in a Buick, smoked like a tar bucket and rattled so bad it sounded like a diesel. The GM dealer who did this treatment said it was the carbon being disolved and burning off. Went on to put another 350,000 miles on the same engine, with no further mechanical problems.
Stan in LA (lower AL)
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AgTires4295
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Tractors Owned: 1940 Farmall A
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Re: '51 Cub Power Issues

Postby AgTires4295 » Wed Apr 22, 2015 7:54 pm

Well that's a relief! Glad to know! Maybe I'll give it another dose then when I can get back around to it. It just didnt sound right at all. I didnt want to hydrolock it or bend a connecting rod.
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Re: '51 Cub Power Issues

Postby Clark Thompson » Wed Apr 22, 2015 9:42 pm

Charging the battery indicates to me that the coil may be weak. I would take the spark plugs out to see if soot is on them. Just this last winter I needed some gas in my cub that sets a lot. When I parked it last fall it was running rich and missing. To make a long story short I buy laquer thinner by the 5 gallon can, I use the laquer can for a gas can when the laquer is used up . Then I buy more laquer in a 5 gallon can. Anyway I needed gas for the cub and you guess what I did. I poured a gallon of laquer in the cub tank by accident!. Fired right up. ran great! and after a half hour of running the engine stopped missing and idled very smooth. Had lots of power. I also noticed it wasnt making any more blue smoke out the exhaust like it did last fall. Ran it out of fuel again. Added gas this time to be sure! Fired up and still runs better than it ever did. :{_}:
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Re: '51 Cub Power Issues

Postby Scrivet » Thu Apr 23, 2015 6:58 am

AgTires4295 wrote:........... I then squirted the Seafoam and at one point, the engine started to knock! This scared the heck out of me so I immediately backed off. What was making that horrible knock??? Was that the engine beginning to hydrolock from the Seafoam spray??..............
My opinion is there is no way you can get enough Seafoam into the engine to hydrolock it and it keep running. I use a spray bottle that mists the spray and direct it into the carb. I can kill the engine with enough of that mist spray, not because there's to much liquid but because the air to fuel ratio gets to far off to burn. I personally wouldn't let a short lived knock bother me especially during a "breathing treatment". Just go hummm, mumble "that's odd" and only be concerned if/when it reoccurs.

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AgTires4295
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Posts: 197
Joined: Fri Dec 30, 2011 7:36 pm
Zip Code: 20646
Tractors Owned: 1940 Farmall A
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1970 Cub Cadet 127
1970 Simplicity Broadmoor 728 (x2)
1984 Cub Cadet 782
1964 Simplicity Landlord
2014 Simplicity Broadmoor 23/50
Location: La Plata, MD

Re: '51 Cub Power Issues

Postby AgTires4295 » Thu Apr 23, 2015 10:04 am

Clark Thompson wrote:Charging the battery indicates to me that the coil may be weak. I would take the spark plugs out to see if soot is on them. Just this last winter I needed some gas in my cub that sets a lot. When I parked it last fall it was running rich and missing. To make a long story short I buy laquer thinner by the 5 gallon can, I use the laquer can for a gas can when the laquer is used up . Then I buy more laquer in a 5 gallon can. Anyway I needed gas for the cub and you guess what I did. I poured a gallon of laquer in the cub tank by accident!. Fired right up. ran great! and after a half hour of running the engine stopped missing and idled very smooth. Had lots of power. I also noticed it wasnt making any more blue smoke out the exhaust like it did last fall. Ran it out of fuel again. Added gas this time to be sure! Fired up and still runs better than it ever did. :{_}:


Wow what a tank! I'll admit, mine is an oil burner (hence the Seafoam treatment to free up the rings as best as I can). I just put new plugs in it maybe an hour of runtime prior to the power issues to rule them out. The other ones were fine (and only a year old) but had a ton of soot caked on them. I dumped much of the Seafoam in the fuel tank so hopefully a healthy dose is setteling in there and everywhere else, doing its job while waiting for me to start it next.

I'm hoping the rings will free up because a teardown for me at this point will nearly be impossible because of time constraints. Im almost scared to take the head off and look at the cylinder walls but they cant be that bad... not after it has been running so well!
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1940 Farmall A
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