What just happened?!?!

[GregoryU]

I bought a 1950 AR a while back. Ran great. NO problems other than the clutch slipping. I replaced the clutch discs last week and drove it a couple times to get it set. Drove it out of the shed Saturday...ran it back in at the end of the day. Ran perfectly. Old timey show coming up this weekend so I went to start it up and wash it, thought I might take it to show. Cranked and cranked on it. Doesn't really like any/very much choke. Wouldn't pop. Finally choked it a bit and kept cranking. Finally started up. BUT...ran rougher than a cob. Backfire...bad! Fire out of the exhaust about six inches bad! Almost shut it off, afraid I'd blow the muffler up. Now it idles rough, and now the tractor seems to be vibrating. I honestly think I blew some baffles out of the muffler cause it sure sounds louder/rougher now. Anybody with ideas here?? This absolutely floored me today, never had anything like this happen. I haven't looked at anything yet had other things to do and quite frankly pretty shocked with what happened.

 

[Ray,IN]

Sounds kinda like an exhaust valve stuck open.

 

[used red MN]

Check the plugs for being fouled with black soot from being flooded or ran rich. If black clean them with a spray carb cleaner, a wire brush and compressed air.

 

[Fixingfarmer]

I’m not sure where you live but just the condensation from all the humidity around here causes plug problems this time of year just like they say

Mine will run skipping a cylinder for a minute then pickup. I was a hair lean and it was backfiring last week too. 2 cylinders do that when lean or rich

Could be a carb issue but I’d try plugs first clean them off and check gap at the very least

Usually mine makes it through to the end of the year now and then I just replace them once a year mowing is almost done

 

[JIM MN]

You washed it?

 

[GregoryU]

Thanks for the replies! Nope, didn't wash it. Didn't get that far. Tomorrow I'll check the plugs and take off the valve cover and check the valves to see if they're free. Really blew me away...it's run perfectly the 3 months I've owned it. Was looking forward to finally showing it and my 49 at the show this weekend. Kinda took the wind out of my sails and I passed on that idea.

 

[used red MN]

I'll check the plugs and take off the valve cover and check the valves to see if they're free.

In my opinion if you check the plugs and they appear to be the problem no need to poke around under the valve cover unless you really want to look in there or set the valves. Since you have two screw the plugs out of the one that runs good and try them in the other one. Then you will immediately know if the plugs were the problem or not.

 

[GregoryU]

I've been checking some things on the AR. I took the valve cover off...valves are free. Replaced the sparkplugs. Same thing, won't hardly start, when it does, still backfires and runs rough. Checked the spark with my inline tester. Light spark on the right hand side. No spark on left. Cleaned everything in the mag and still nothing. So, did my mag take a dump on me? Somethin else?

 

[Fixingfarmer]

Do they take the same mag? If the 50 has a mag the 49 should?

That would be how I’d test this and know for sure

 

[a49deere]

I've been checking some things on the AR. I took the valve cover off...valves are free. Replaced the sparkplugs. Same thing, won't hardly start, when it does, still backfires and runs rough. Checked the spark with my inline tester. Light spark on the right hand side. No spark on left. Cleaned everything in the mag and still nothing. So, did my mag take a dump on me? Somethin else?

did you test at plug end of plug wire or at the mag port itself? Did you test it on bench or tractor? Are you getting good snap-on impulse spring when rotated? clean ground? Point gap, clean? Another thing to check would be the shaft bushings for slop, causing the points to not open and close correctly!

 

[Mark-Ia]

Bad condenser.

 

[GregoryU]

I'll have to check and see if they're the same mag. I put my inline tester between the plug/wire. Just did a quick cleaning of the points, rotor parts, then only took time to check with the inline again. Next time I go out I'll make some new plug wires to eliminate the wires first. Then start on the mag. Thanks for the replies.

 

[David from Kansas]

Have a '51 with distributor. Had a similar situation a few years ago and it turned out to be the condenser. Try the small stuff first before you dig too deep. I have also had a carburetor problem which required a carb rebuild. Is now starting and running perfectly. There is a you tube video "Plowing with the John Deere 51 AR" where I was pulling the guts out of it on some dry, hard packed wheat stubble.