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John Deere L tractor with Hercules eng., TIMING!


 
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Jim R
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PostPosted: Mon Jun 04, 2012 2:35 pm    Post subject: John Deere L tractor with Hercules eng., TIMING! Reply to specific post Reply with quote

I have a friend who recently got a 1939 John Deere L tractor with the Hercules engine and a Wico "X" Magneto. We have had the magneto, and carb. rebuilt and got the tractor to run by towing it. It idles and runs Great with no smoke, But we just can't seem to get it started by cranking it! You have to tow it to get it started. I've been told to play with the timing a little, to see if that makes a difference. Can someone out there tell me how to set the timing and where to set it to get it to start better? I am no mechanic and will probably take it back to the one who installed the magneto, but I could use the advise of one of you JD Guys as to where we should set the timing. I believe he set it at T.D.C. Should we advance or retard it? I have a reproduction manual but the part that tells about timing doesn't explain it very well. Any help or advise would be appreciated!
 
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PopinJohn
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PostPosted: Mon Jun 04, 2012 3:44 pm    Post subject: Re: John Deere L tractor with Hercules eng., TIMING! Reply to specific post Reply with quote

If it starts and runs okay after pull starting, my guess is that the impulse in the magneto isn't working.
Possibly the impulse spring is broken.
Possibly the spring was wound backward, since WICO #909 magnetos rotate opposite from WICO's on JD ABG tractors.
If the magneto is timed properly, the impulse trips when the #1 piston tips over top dead center. I don't remember if #1 is the front or rear cylinder.
Mike Shelby
 
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jdal
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PostPosted: Mon Jun 04, 2012 5:28 pm    Post subject: Re: John Deere L tractor with Hercules eng., TIMING! Reply to specific post Reply with quote

I have a 39 L with Hercules and it starts great usually once over with choke on and next time over it starts even though the compression is poor. It does sound like a mag impulse problem. Can you hear the impulse "snap" when you crank it? I've used both a Wico and currently have an Edison-Splitdorf on it, both act the same. Good luck.
 
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Hotflashjr
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PostPosted: Tue Jun 05, 2012 4:12 am    Post subject: Re: John Deere L tractor with Hercules eng., TIMING! Reply to specific post Reply with quote

#1 is the front cylinder closest to the radiator.
 
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Hotflashjr
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PostPosted: Tue Jun 05, 2012 4:15 am    Post subject: Re: John Deere L tractor with Hercules eng., TIMING! Reply to specific post Reply with quote

I have a couple of original dealer L and LA repair manuals at home. I will try and make some time tonight to read over the timing procedure. We just got a new Mac and I'll be darned if I can get it to post a picture to this website. If I can I will scan and post the pages that deal with timing. I am not positive I have the correct procedure for the Hercules engine but I know I have it for the JD made engine with the Wico XH-909 magneto. Maybe swtiching to an Edison-Splitdorf or Wico C may cure the issue sinec those were both used on L's before the Wico XH?
 
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Jim R
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PostPosted: Tue Jun 05, 2012 4:26 am    Post subject: Re: John Deere L tractor with Hercules eng., TIMING! Reply to specific post Reply with quote

THANKS so much for your advise! I"m glad to know that someone else has a JD, L with another Hercules engine and is able to tell me how they get theirs started! Even with low compression it starts ok, ha. I was wondering if I had a compression problem, but I really don"t think so because it really doesn"t feel like it, and when we do get this one started by towing it, it runs Great and idles so slow, it"s amazing! This suggestion of a magneto impulse problem makes sense! I"m not a mechanic, as I said, but I understand how the magneto works. I will take the tractor back to the guy that worked on the magneto and have him do some more checking, but won"t be able to do it until this coming Saturday. With everything else that we"ve done to the tractor, it just has to be a magneto problem, either impulse problem or timing. I do hear the impulse spring when I crank over the engine. What should the timing be set at ideally, to be able to get it started with a crank? I will post the results here, when we finally get the problem figured out. Thanks again for all your advise!
 
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Pete in MD
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PostPosted: Tue Jun 05, 2012 8:47 am    Post subject: Re: John Deere L tractor with Hercules eng., TIMING! Reply to specific post Reply with quote

Since it runs good after tow starting I would say the "run" timing is correct and that the "start" timing is what needs adjustment.

With the plugs out roll the engine over until #1 is coming up on compression and listen for the mag impulse to trip. It should trip at TDC. If it doesn't you need to make an adjustment on the backside of the mag. Before you remove the mag, roll the engine over again until #1 is at TDC. Make an index mark on the mag and mating surface so you can reinstall the mag at the same position.

On the backside you'll see the impulse coupling with a stamped "degree" marking--probably 25 degrees. Whatever degree is marked on the coupling is what the impulse has to be "retarded" to so the impulse will trip at TDC when cranking. Near the top of the coupling there are 11 marks (5 tall ones and 6 short ones). Just below these marks you'll see a single mark on a ring that is movable by loosening 4 screws. When the mark on the ring is lined up with the middle mark of the 11 marks the impulse is 12-1/2 degrees retarded. The distance between each of the 11 marks is 5 degrees. If your impulse coupling is marked 25 degrees, then you need to rotate the ring so the mark on it is 2 and 1/2 marks to the left. This gives a total of 25 degrees. When you have it set, tighten the 4 screws and reinstall the mag. While you're doing the above don't move the impulse coupling.
 
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DaveinNJ
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PostPosted: Tue Jun 05, 2012 6:08 pm    Post subject: Re: John Deere L tractor with Hercules eng., TIMING! Reply to specific post Reply with quote

My 1940 Model L with the Hercules engine has a flywheel with two marks on it. TDC and spark (or "SPK" or "SPRK" perhaps).

We set the timing with an automobile timing light, with the magneto sparking right when "SPK" is visible in the timing hole on the flywheel housing.

BTW before timing, we disconnected the plug wires. Then stuck a finger in the hole, turned the crankshaft/flywheel and wiped off the flywheel so the marks were visible. Then reconnected and set the timing. Dave
 
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Pete in MD
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PostPosted: Tue Jun 05, 2012 6:27 pm    Post subject: Re: John Deere L tractor with Hercules eng., TIMING! Reply to specific post Reply with quote

Dave,
What you're describing is the "run" timing. I think Jim's problem is with the "start" timing.
Pete
 
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Hotflashjr
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PostPosted: Wed Jun 06, 2012 3:04 am    Post subject: Re: John Deere L tractor with Hercules eng., TIMING! Reply to specific post Reply with quote

This is exactly what the repair manual says to do if the mag has been removed and needs to be timed before putting it on the tractor. I think this is where the issue is as well.
 
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Jim R
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PostPosted: Wed Jun 06, 2012 4:43 am    Post subject: Re: John Deere L tractor with Hercules eng., TIMING! Reply to specific post Reply with quote

Thanks so much, again to all you guys for your advise. As I said, it will be Saturday, June 9th before I can get the tractor to the guy that did the Magneto work, to get it set right. I will post the results and what we ended up doing to try to get it right. I really appreciate the help from all you guys!
 
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Jim R
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PostPosted: Sat Jun 09, 2012 9:13 pm    Post subject: Re: John Deere L tractor with Hercules eng., TIMING! Reply to specific post Reply with quote

Ok Guys, it is now Saturday night, June 9th. I promised I would report the outcome of this problem after I took the tractor back to the guy that checked out the magneto. The tractor, now wouldn"t start, even with towing it. We determined that we had No spark coming from the magneto, so the magneto guy that I took the tractor to, removed the magneto again and tested it out. I had put a "Hot Coil" in the magneto that we bought from Roberts Carb. Repair, in an effort to make the tractor start easier with the crank. It turns out that the new "Hot Coil" was only putting out a weak spark, and then none at all. This magneto repair man is the Best in the state and maybe, several states. He had in stock, an original Wico replacement Coil, which he installed in the magneto, and put it all back on the tractor. The tractor now starts GREAT with the crank, usually one crank with the choke and the next crank with the choke off and it"s running! The "Hot Coil" that I originally put in the magneto never did work right, from the start. Everything is working great now! Thanks for all your help and advise! You are a great bunch of guys out there!
 
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