Got Mag Back - Backfires

txasylum

Member
I got my rebuilt mag back today. I put it on my 28 JD D. I hooked up my spark plugs to view the spark. I turned it over and when the LH Spark Retard on the flywheel lined up with the mark on the housing, my number one plug sparked. I turned it to near LH Exhaust open and number two spark.

So that is okay. I put a little bit of gas in number two plug hole, put plug in. I have not put number one in yet, turn it over and when sparked it backfired and a flame shot out of the number one hole.

I decided to put number one in, turn it over and bam,another loud crack and a very impressive flame out the exhaust.

Scared the crab out of me!

What am I doing wrong?

Bob
 
Reverse your spark plug wires in the mag. Your mag can be installed in two positions. Normally, the spark occurs each time the piston reaches the top of the stroke. No doubt, yours is 180 degrees off, and is firing at the bottom of the stroke.
 
After a little more research, I do have the timing set right. NOt sure why it backfired initially, but now it is trying to fire over but it doesn't keep the momentum going. This is what it was doing when I decided to rebuild the mag. But now it is doing the same thing. I can only spin it a few times before I'm worn out. I will have to try to get someone to help me by pulling starting it. Anyone in the Western PA area?
 
you could belt it up to another tractor. Takes a lot of gas to get those old D's to run. You almost can't flood them.
 
I wish I had a belt. I don't know of anyone around here with belts or any old Deeres. I was just talking to my dad on the phone. He lives a couple of hours away and he mentioned a belt, but again out of luck with the belt.

Will try again tomorrow. I'm worn out now.
 
On my D it was 180 out when i tried to start it BAM.I was in my shop when it backfired. It has 4 inch dual 24inch tall strait pipes on it. I was right beside it when I was hand starting it. Rung my ears real good.
 
Does your carb have that spring action on the choke? I have to have someone hold on the choke while I turn the flywheel on mine. Also does yours have the priming cups on the compression releases. Fill those things a couple of times on each cylinder while the piston is just starting on the compression stroke. Remember those cylinders are about the size of a gallon paint can. Needs a lot of gas. check out my video on you tube "starting my 1928 john deere D" Have fun!
 
Reminds me of Forbe Rose back in the early 70s when I helped him gather hay out of the bar ditches in late summer. He would cut it with his D and watching this worn out old man who couldn't tip the scales at 90 lbs. start that beast was a highlight of the week for sure. He had the petcocks turned upside down and he would open them up and put in an old style, long spout oil can with gas in it and pump on the bottom of the can with his thumb until most of the gas had made it into the cylinder, fiddle around a bit filling the oil can back up and then he would toddle over to the other side and do that one too. One eighth of a turn or less at a time he would roll over that monster and eventually she would jump when that mag went ker-lank and off she was a running.

And then the real show would start because as soon as he could reach the valve, he would switch it over to distillate even though you are supposed to wait until the engine is very warm to do that first - he was just too tight to care about following directions or listening to reasons why. At any rate, the magnificent snorting and backfiring that occurred while the engine was too cold to vaporize the distillate was something every JD enthusiast needs to see at least once. The tractor would almost lift itself clear of the ground sometimes as smoke rings exited the exhaust fast enough to knock down birds from the sky, I swear a hundred feet up on rare occasion. Followed by a miniature explosion it was all a very grand show for me to witness at a distance of the hay stack. Soon enough she would settle down and get to business with no more objections. And we spent the rest of the day cutting kochia weeds with it. But that was a one man job so I was given a garden hoe and told to go uproot sunflowers in the half section of summer fallow - talk about mission impossible, as there were thousands upon thousands if not a full million already knee high or better, it all made for a really long day.

I was being paid $1.50 an hour and that was a very good wage as most others were only getting $1.25 that summer.
 
Pull the plugs out and see if it fires #2 at the top of compression for that one. Just helps to double check.

I can"t remember, are your valves adjusted correct?

The old Ds do love to backfire. Especially with your Wico C mag, where they fire on the exhaust stroke. It should fire up and run just fine as is.

Brandon
 
Yeah, it is firing on #2 compression stroke. It wants to fire over, but just doesn't keep the momentum going. May not be getting enough fuel. It starts when I pull it (at least last time it did), but I don't have anyone here to help me by pulling me. So been wearing myself out by hand cranking it.
 
If you've been fighting a lot, don't forget to take out the plugs and dry 'em and even replace.

Don't be afraid to richen up the idle and load needles on the carb a few clicks, maybe even half a turn or more.

Don't be afraid to chcke too.

I really sympathize with ya, I spent lots of time trying to start a cantankerous '28. Rebuilt carb and mag and figuring out the right settings helped a WHOLE lot.

Brandon
 
(quoted from post at 01:41:08 05/11/13) I wish I had a belt. I don't know of anyone around here with belts or any old Deeres.

I'm in Grove City and would gladly belt my 620 up to your D if you can find a belt, would love to hear that thing run.
 
I have seen a few belts on Ebay, but if you are close (about 10 miles from me), can you run my other tractor and pull me to jump start it?
 
(quoted from post at 13:42:22 05/12/13) I have seen a few belts on Ebay, but if you are close (about 10 miles from me), can you run my other tractor and pull me to jump start it?

sure we could do that, where you at?
 
I am off of Boyers Road, on Ferguson Rd. About 5 miles from Harrisville.

give me a call at 724-304-0500
Bob
 

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