420 questions UPDATE

grandpa Love

Well-known Member
Got up yesterday and put new spark plugs and wires on it. Also new battery cables. Fired right up! But.... Still backfiring out the carb. Pulled valve cover. Cotter pin on front of rocker arm assembly was broken and the washer and spring had fallen off. The front rocker arm was wedged in place, off the top of valve. Push rod was bent, I straightened it to about 98 percent good. But the front valve is stuck. Taps down fairly easy with a hammer, but can't tap up with head on. Took keepers off and discovered that valve spring in bent and deformed. Off with it's head!! Would really like to get one valve spring and maybe a push rod, just to get it running. We could then check transmission, lift and pto. If it checks out, we will probably buy the darn thing. Got our youngest son and my dad trying to talk us into it. Anyone have a spare spring and rod I can buy? Also, not sure if it's an issue ,the tube the rocker arms ride on is bent up just enough to notice on the front. That rocker arm sits nice on valve and rod. Can I just adjust the valve to fit the bend?? Thanks!
 
Can you get a piece of say 5/16 rod and bend a curve into it so you can go in the spark plug hole and push the valve back up? If you can work it up and down and get penetrating oil worked into it I'll bet it will free up without pulling the head. You can readjust the valve clearance with the bent push rod to see how it runs but it's not a long term fix. You could also use the distorted spring just to see how it runs.
 
Kevin,

Have two heads (cracked) off an MT with springs, think I have push rods and one rocker arm. Email is open. Let me know what you need. I have freed up valves by removing the springs and chucking up the stem in a battery drill and adding penetrate. Reverse drill back and forth until you get it to turn a full turn. Then pull up on the drill so the valve head and seat will rub any carbon off. Might want to put pliers on stem and get it to turn a little first.
 
as i said before stuck valves. pulling the valve cover was first on the list you did all this damage by trying to start it with out going through the proper procedure. when a valve is stuck it will definitly bend the pushrod . on any engine sitting for years you remove valve cover and give the valves a tap or push to see if they will move. spark plugs dont make a backfire neither does wires unless they are all bound together and the spark takes a short cut. and the pushrod must be straight! if you cant get it staight then get another one. the john deere dealer will be able to get these parts or from a tractor wrecker. also once head is off pull ALL the valves out... clean the stems and bores and lube them then install again. post some pictures of them valves as they might be ready for a regrind or renew also. the guides have rust in them and you dont want that left in there as that will just wear them more. you are working backwards causing more work and money in the end.
 
Rustred, I did all the damage? I don't believe so. Someone else fooled with it about a year ago. According to my elderly friend that guy couldn't get it to run right, he said it needed a new carb.
 
(quoted from post at 05:51:00 10/17/21) Got up yesterday and put new spark plugs and wires on it. Also new battery cables. Fired right up! But.... Still backfiring out the carb. Pulled valve cover. Cotter pin on front of rocker arm assembly was broken and the washer and spring had fallen off. The front rocker arm was wedged in place, off the top of valve. Push rod was bent, I straightened it to about 98 percent good. But the front valve is stuck. Taps down fairly easy with a hammer, but can't tap up with head on. Took keepers off and discovered that valve spring in bent and deformed. Off with it's head!! Would really like to get one valve spring and maybe a push rod, just to get it running. We could then check transmission, lift and pto. If it checks out, we will probably buy the darn thing. Got our youngest son and my dad trying to talk us into it. Anyone have a spare spring and rod I can buy? Also, not sure if it's an issue ,the tube the rocker arms ride on is bent up just enough to notice on the front. That rocker arm sits nice on valve and rod. Can I just adjust the valve to fit the bend?? Thanks!

The valve spring is DEERE part # M102T, GOOGLE will find you all sorts of them, new ones are still available from DEERE for about $15, as well.

Pushrod, #AM2849T is still available from DEERE, as well, but $$$. (I will check, I MAY have some new pushrods.)

LOTS of alternate sources on the 'net.

If you haven't pushed the valve down so far you can't grab it (or can push it up with rope above the piston, as another poster suggested) grab the upper area of the valvestem with the chuck of a 1/2" electric VSR drill.

Tighten the chuck TIGHT. REALLY tight! then spin the sticky valve while keeping the stem wetted with penetrating oil.

Keep at it, working the spinning valve up and down in the guide and keep up with the penetrating oil 'til the valve frees up.

https://partscatalog.deere.com/jdrc/sidebyside/equipment/67961/referrer/navigation/pgId/70883
 
well ok then who ever turned that engine over did the damage . u just said it was sitting. so how am i to know with out info.??? plus u did not listen to what i said anyhow. so why ask for help? then people get ------ cause they think i shouldnt be so hard on them. well if your working in a shop for example and the shop foreman says did you check compression and you say no and start putting other parts on then your in a lot of chit! i got lots of engine experience being a ticketed mechanic also. then some backyard hill billy tells you to fill the muffler with auto trans fluid so it loosen valves... well that is so much b.s. i just shake my head. all of us are here to help each other but it appears some that know nothing are god. any of these little engine problems you guys have is a drop in the bucket to what i can do. and my answers are actual hand on experienced problems lots of times. i also notice some guys look up the problem on the computer then add that to a post of theirs. they have never even had hands on experience. i always say check compression when doing a tune up ... its standard procedure. so many people say i replaced the plugs and engine is missing and backfiring ,... well do the job properly and you will find the miss your self. hope u guys learn something by not listening to screwdriver and oil can mechanic's.
 
Kevin,

Failed to find an email from you after checking regular, spam and trash folders as well. Give me a call at 662 six one seven 2346. Leave message with a good time to call you back if no answer. I have several parts tractors you might be interested in Starkville, MS.
 

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